Biochemical effects of the antidepressant paroxetine, a specific 5-hydroxytryptamine uptake inhibitor

Differential effects of paroxetine on raphe and cortical 5-HT1A binding: a PET study in monkeys

Positron emission tomography (PET) ligands that are sensitive to transient changes in serotonin (5-HT) concentration are desirable for studies of neuropsychiatric diseases. Few studies, however, have sought to demonstrate that variations in 5-HT concentration can be closely tracked with available serotonergic ligands. Microdialysis studies in rats have shown a maximal increase in 5-HT concentration in raphe nuclei after systemic infusion of selective serotonergic re-uptake inhibitors (SSRIs). We performed PET scans with [(18)F]FPWAY, an intermediate-affinity antagonist of 5-HT(1A) receptors, in 4 anesthetized rhesus monkeys in control studies and after systemic paroxetine administration (5 mg/kg, i.v.). In addition, a paired [(11)C]DASB study revealed that this paroxetine regimen produced an occupancy of 54-83% of the serotonin transporters. According to the conventional receptor competition model, increased 5-HT concentration produces decreased binding of the radioactive ligand. Over a 3-h period following paroxetine infusion, a progressively increasing reduction (ranging from 8 +/- 6% to 27 +/- 10%) of [(18)F]FPWAY-specific binding was found in the raphe nuclei. This result is interpreted as an SSRI-induced increase in 5-HT concentration, potentially combined with reduced binding to internalized 5-HT(1A) receptors. In addition, a transient (1 h) increase in cerebral cortical binding was observed, attributed primarily to a reduction in cortical 5-HT due to the effects of raphe autoreceptor inhibition. This study is the first demonstration of the feasibility of quantifying dynamic changes in 5-HT neurotransmission in the raphe and the cortex with PET. These results lend promise to the use of these serotonergic neuroimaging techniques to study neuropsychiatric disorders.

The monoamine-mediated antiallodynic effects of intrathecally administered milnacipran, a serotonin noradrenaline reuptake inhibitor, in a rat model of neuropathic pain

Antidepressants are often used to treat neuropathic pain. In the present study, we determined the antiallodynic effects of selective monoamine reuptake inhibitors in the spinal cord in a rat model of neuropathic pain. Mechanical allodynia was produced by tight ligation of the left L5 and L6 spinal nerves and determined by applying von Frey filaments to the left hindpaw. A serotonin noradrenaline reuptake inhibitor, milnacipran, a selective serotonin reuptake inhibitor, paroxetine, or a selective noradrenaline reuptake inhibitor, maprotiline, was administered intrathecally via a chronically implanted catheter. Milnacipran produced dose-dependent antiallodynic effects at doses between 3 microg and 100 microg. The effect lasted for 7 h after injection of 100 microg (P < 0.05). The antiallodynic effect of 30 microg of milnacipran was attenuated by intrathecal coadministration of 30 microg of yohimbine, an alpha(2)-adrenoceptor antagonist, 30 microg of methysergide, a serotonin receptor antagonist, or 30 microg of atropine, a muscarinic receptor antagonist (P < 0.01, respectively). Intraperitoneal administration of milnacipran had no antiallodynic effects at doses of 3 to 30 mg/kg. Antiallodynic effects were not produced by intrathecal administration of paroxetine (10 to 100 microg) or maprotiline (10 to 100 microg). These findings suggest that simultaneous inhibition of serotonin and noradrenaline reuptake in the spinal cord is essential to mediate antiallodynic effects. Milnacipran might be effective for suppression of neuropathic pain.

Improvement of Dry Mouth by Replacing Paroxetine with Fluvoxamine

OBJECTIVE:

To present a case of improvement of paroxetine-induced dry mouth by substitution of fluvoxamine and analyze this case based on receptor occupancy theory.

CASE SUMMARY:

A 66-year-old woman with major depressive disorder had been treated with brotizolam 0.5 mg/day, flunitrazepam 2 mg/day, sulpiride 100 mg/day, bromazepam 2 mg/day, trazodone 25 mg/day, and paroxetine hydrochloride 10 mg/day. Although her psychological symptoms improved gradually, she complained of dry mouth. Paroxetine was replaced with fluvoxamine maleate 50 mg/day, and the dryness disappeared within a month.

DISCUSSION:

We calculated the time courses of muscarinic acetylcholine (mACh) receptor occupancy after oral administration of paroxetine and fluvoxamine at the treatment doses by using pharmacokinetic parameters obtained from the literature. The mACh receptor occupancy was estimated to be decreased from 0.22% to 0.020% by replacing paroxetine with fluvoxamine.

CONCLUSIONS:

The improvement of dry mouth observed after the replacement of paroxetine with fluvoxamine in this patient may have been due to a decrease in the mACh receptor occupancy.

Paroxetine controlled release

A controlled-release (CR) formulation of the SSRI paroxetine has been developed. This CR formulation delays the release of paroxetine until the tablet has passed through the stomach; the drug is then released over 4-5 hours. In well designed placebo-controlled trials in patients with major depressive disorder (including a study in the elderly), social anxiety disorder or premenstrual dysphoric disorder (PMDD), paroxetine CR was consistently superior to placebo with regards to primary endpoints (i.e. mean Hamilton Rating Scale for Depression total score [major depressive disorder], Liebowitz social anxiety scale total score and Clinical Global Impressions-Global Improvement score [social anxiety disorder] and Visual Analogue Scale-Mood score [PMDD]). The duration of treatment was 12 weeks or, in PMDD, over three menstrual cycles (intermittent or continuous administration). Paroxetine CR also demonstrated efficacy in three well designed studies in patients with panic disorder with or without agoraphobia. Paroxetine CR was generally well tolerated in clinical trials, with an adverse-event profile typical of SSRIs, although recipients of paroxetine CR experienced significantly less nausea than recipients of immediate-release paroxetine in the first week of treatment.

New formulations of existing antidepressants: advantages in the management of depression

For nearly 50 years, antidepressant drugs have been the first-line treatment for various forms of depression. Despite their widespread use, these medications have significant shortcomings, in particular problems of patient compliance due to adverse effects. The introduction of new formulations of existing antidepressant medications may provide patients with benefits in terms of convenience of use. As a consequence, improvements in compliance may lead to better antidepressant efficiency.An orally disintegrating formulation of mirtazapine (mirtazapine SolTab), a once-weekly formulation of fluoxetine, an enantiomer-specific formulation of citalopram (escitalopram), an extended-release formulation of venlafaxine (venlafaxine XR), a controlled-release formulation of paroxetine (paroxetine CR) and intravenous formulations of some of the newer antidepressants have all been evaluated in limited clinical trials. In this article, a review of the pharmacokinetics and clinical evaluations of these formulations is presented. While there do not appear to be major clinical advantages for the new formulations in terms of antidepressant efficacy, none of them is less efficacious than their older counterpart. Indeed, some of the new formulations are more acceptable to patients (fluoxetine once-weekly, paroxetine CR), others have pharmacokinetic advantages (venlafaxine XR, paroxetine CR), while others may have a faster onset of effect (mirtazapine SolTab, intravenous formulations). Further evaluation of some formulations is still required (mirtazapine SolTab, fluoxetine once-weekly), while others (venlafaxine XR, escitalopram) are finding widespread acceptance in clinical practice.

Effects of clozapine and its metabolites on the 5-HT2 receptor system in cortical and hippocampal cells in vitro

PURPOSE

The goal of the present study was to determine the effects of clozapine (Cloz) and its metabolites norclozapine (Norcloz) and clozapine-N-oxide (Cloz-N-oxide) on the 5-HT(2) receptor system on the levels of protein and gene expression in in vitro systems of primary cortical cells of the rat and human hippocampal SHS5Y5 neuroblastoma cells.

METHODS

Clinically relevant concentrations of Cloz (200/400 ng/ml) and its metabolites (200 ng/ml) were used for the examination of the effects of Cloz and its metabolites on serotoninergic 5-HT(2) receptor parameters (density, affinity and mRNA levels) as well as on glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA levels in primary cortical cells of the rat after treatment for 24 h under in vitro conditions. To compare the results to human cells, we also measured treatment-induced changes in 5-HT(2) and GAPDH mRNA levels in human hippocampal SHS5Y5 cells.

RESULTS

A significant decrease was found in primary cortical cells for 5-HT(2) receptor density (Cloz 200/Cloz 400/Norcloz 200 and Cloz-N-oxide 200 vs. control) and 5-HT(2A) receptor mRNA levels (Cloz 200 vs. control). 5-HT(2A) receptor mRNA levels were also significantly reduced (Norcloz 200 vs. control) in SHS5Y5 cells. GAPDH mRNA levels were not affected.

CONCLUSIONS

The results of the present study show that Cloz and Norcloz induce significant alterations on the 5-HT(2) receptor system in primary cortical cells of the rat and in human hippocampal cells.

Effects of chronic paroxetine treatment on dialysate serotonin in 5-HT1B receptor knockout mice

The role of serotonin (5-HT)1B receptors in the mechanism of action of selective serotonin re-uptake inhibitors (SSRI) was studied by using intracerebral in vivo microdialysis in conscious, freely moving wild-type and 5-HT1B receptor knockout (KO 5-HT1B) mice in order to compare the effects of chronic administration of paroxetine via osmotic minipumps (1 mg per kg per day for 14 days) on extracellular 5-HT levels ([5-HT]ext) in the medial prefrontal cortex and ventral hippocampus. Basal [5-HT]ext values in the medial prefrontal cortex and ventral hippocampus, approximately 20 h after removing the minipump, were not altered by chronic paroxetine treatment in both genotypes. On day 15, in the ventral hippocampus, an acute paroxetine challenge (1 mg/kg i.p.) induced a larger increase in [5-HT]ext in saline-pretreated mutant than in wild-type mice. This difference between the two genotypes in the effect of the paroxetine challenge persisted following chronic paroxetine treatment. Conversely, in the medial prefrontal cortex, the paroxetine challenge increased [5-HT]ext similarly in saline-pretreated mice of both genotypes. Such a challenge produced a further increase in cortical [5-HT]ext compared with that in saline-pretreated groups of both genotypes, but no differences were found between genotypes following chronic treatment. To avoid the interaction with raphe 5-HT1A autoreceptors, 1 micro m paroxetine was perfused locally through the dialysis probe implanted in the ventral hippocampus; similar increases in hippocampal [5-HT]ext were found in acutely or chronically treated wild-type mice. Systemic administration of the mixed 5-HT1B/1D receptor antagonist GR 127935 (4 mg/kg) in chronically treated wild-type mice potentiated the effect of a paroxetine challenge dose on [5-HT]ext in the ventral hippocampus, whereas systemic administration of the selective 5-HT1A receptor antagonist WAY 100635 did not. By using the zero net flux method of quantitative microdialysis in the medial prefrontal cortex and ventral hippocampus of wild-type and KO 5-HT1B mice, we found that basal [5-HT]ext and the extraction fraction of 5-HT were similar in the medial prefrontal cortex and ventral hippocampus of both genotypes, suggesting that no compensatory response to the constitutive deletion of the 5-HT1B receptor involving changes in 5-HT uptake capacity occurred in vivo. As steady-state brain concentrations of paroxetine at day 14 were similar in both genotypes, it is unlikely that differences in the effects of a paroxetine challenge on hippocampal [5-HT]ext are due to alterations of the drug's pharmacokinetic properties in mutants. These data suggest that there are differences between the ventral hippocampus and medial prefrontal cortex in activation of terminal 5-HT1B autoreceptors and their role in regulating dialysate 5-HT levels. These presynaptic receptors retain their capacity to limit 5-HT release mainly in the ventral hippocampus following chronic paroxetine treatment in mice.

Influence of synaptic serotonin level on [18F]altanserin binding to 5HT2 receptors in man

The feasibility of in vivo serotonin 5HT(2) receptor binding measurement using [18F]altanserin as a radioligand has been well established. In this study, the postsynaptic receptor binding potential of this ligand was examined as a possible indicator of synaptic serotonin content after pharmacological challenge. Studies were performed in 11 subjects with a history of recurrent major depression. Six of them received serotonergic antidepressive treatment at the time of the experiment, the other five patients were untreated. Two PET measurements were carried out in each subject within 2 or 3 days. Before one of the measurements, 25 mg of the serotonin re-uptake inhibitor clomipramine were given intravenously, the other measurement was done without pharmacological challenge. The data were analyzed using non-linear least-square regression and Logan's graphical method. In the whole group of subjects, binding potential and distribution volume of altanserin decreased following clomipramine challenge. The decrease was between 14 (P=0.03) and 23% (P=0.004). This effect was mainly seen in subjects not on antidepressive medication. Clomipramine challenge probably increased the synaptic serotonin level, which competed with altanserin leading to the lowered binding potential. The paradigm might, thus, be useful to estimate serotonin release in vivo. Pretreatment with serotonergic antidepressants reduces the effect of clomipramine.

Serum leptin levels in patients with premature ejaculation before and after citalopram treatment

OBJECTIVE

To evaluate serum leptin levels (an adipocyte hormone involved in the suppression of appetite) in patients with premature ejaculation before and after treatment with citalopram, a selective serotonin reuptake inhibitor, with the hypothesis that leptin levels might become normal during this treatment.

PATIENTS AND METHODS

The inhibitory effect of serotonin on libido, ejaculation and orgasm is well documented. Although there is no direct evidence of an association involving brain pathways which are related to sexual behaviour, there is an interaction between leptinergic and serotonergic systems. In a previous study serum leptin levels were high in patients with premature ejaculation. The present study comprised 30 patients with premature ejaculation according to the Diagnostic and Statistical Manual of Mental Disorders Third Revised Version. Fifteen patients (group I) were randomly assigned to 8 weeks of citalopram treatment and the remainder (15, group II) received no therapy. The patients were asked to determine the average intravaginal ejaculation latency time, and their fasting serum leptin levels were measured at baseline and after 8 weeks.

RESULTS

There was no significant difference in the mean intravaginal ejaculation latency time between the groups at baseline; it increased after 8 weeks of treatment with citalopram in group I, to a mean (sd) of 209 (72.1) s, but not in group II. No difference was detected in leptin levels between the groups at baseline, but at 8 weeks they were lower in group I.

CONCLUSION

As hypothesized, leptin levels decreased in patients with premature ejaculation after treatment with citalopram, and this decrease seemed to be linked to the therapeutic effect. Further experimental studies are needed.

Paroxetine-induced enuresis

I would like to include one case to the literature on children and adolescents who have developed enuresis while taking paroxetine. Up to now, the fact that enuresis may have occurred as a result of the side effect of using paroxetine was not reported in some articles and letters.

Rat strain differences in peripheral and central serotonin transporter protein expression and function

Female Fischer 344 (F344) rats have been shown to display increased serotonin transporter (5-HTT) gene expression in the dorsal raphe, compared to female Lewis (LEW) rats. Herein, we explored, by means of synaptosomal preparations and in vivo microdialysis, whether central, but also peripheral, 5-HTT protein expression/function differ between strains. Midbrain and hippocampal [3H]paroxetine binding at the 5-HTT and hippocampal [3H]serotonin (5-HT) reuptake were increased in male and female F344 rats, compared to their LEW counterparts, these strain differences being observed both in rats of commercial origin and in homebred rats. Moreover, in homebred rats, it was found that these strain differences extended to blood platelet 5-HTT protein expression and function. Saturation studies of midbrain and hippocampal [3H]paroxetine binding at the 5-HTT, and hippocampal and blood platelet [3H]5-HT reuptake, also revealed significant strain differences in Bmax and Vmax values. Although F344 and LEW rats differ in the activity of the hypothalamo-pituitary-adrenal (HPA) axis, manipulations of that axis revealed that the strain differences in hippocampal [3H]paroxetine binding at 5-HTTs and [3H]5-HT reuptake were not accounted for by corticosteroids. Hippocampal extracellular 5-HT levels were reduced in F344 rats, compared to LEW rats, with the relative, but not the absolute, increase in extracellular 5-HT elicited by the local administration of citalopram being larger in F344 rats. Because the aforementioned strain differences did not lie in the coding sequences of the 5-HTT gene, our results open the promising hypothesis that F344 and LEW strains model functional polymorphisms in the promoter region of the human 5-HTT gene.

Focus on paroxetine

This review of paroxetine is based on Medline and PsycLit searches and a manual search of the available research literature. It aims to cover the pharmacology of this frequently prescribed SSRI antidepressant in terms of its indications, efficacy and adverse effects. Overall, paroxetine is a well-tolerated and safe first-line SSRI antidepressant with anxiolytic qualities. It has been found useful in depression, anxiety and other conditions such as obsessive compulsive disorder and post-traumatic stress disorder. The antidepressant has some advantages over earlier tricyclic medication in terms of a lack of cardiovascular side-effects and relative safety in overdose. Cessation of use, however, is associated with withdrawal or discontinuation symptoms and patients should be counselled as to how these might be avoided. A 3- or 4-week graded withdrawal regimen, perhaps with concomitant fluoxetine to cover serotonergic discontinuation symptoms, may be advisable.

Comparison of the effects of antidepressants on norepinephrine and serotonin concentrations in the rat frontal cortex: an in-vivo microdialysis study

The present study employed in-vivo microdialysis techniques in the freely moving rat to systematically compare the neurochemical effects of various antidepressant agents on extracellular concentrations of norepinephrine (NE) and serotonin (5-HT) in the frontal cortex. We found that acute administration of the tricyclic antidepressant, desipramine (3-30 mg/kg, s.c.) and the dual serotonin/norepinephrine reuptake inhibitor, venlafaxine (3-30 mg/kg, s.c.), produced dose-dependent and robust increases in cortical NE concentrations (498% and 403%, respectively). Conversely, acute injection of the selective serotonin reuptake inhibitors, fluoxetine (30 mg/kg, s.c.) and paroxetine (1-10 mg/kg, s.c.), did not alter forebrain NE concentrations. However, paroxetine did produce a significant increase in cortical NE concentrations (164%) when administered at 30 mg/kg. These changes in NE were not paralleled by 5-HT, which showed no increase following administration of desipramine, venlafaxine, paroxetine or fluoxetine. Combination treatment with the 5-HT1A receptor antagonist, WAY-100635 (0.3 mg/kg, s.c.), significantly enhanced extracellular 5-HT concentrations following venlafaxine (10 and 30 mg/kg), fluoxetine (30 mg/kg) and paroxetine (3-30 mg/kg). Alternatively, WAY-100635 produced no augmentation of the antidepressant-induced changes in extracellular NE. Collectively, these studies show that paroxetine, at low to intermediate doses, and fluoxetine are selective for 5-HT versus NE systems, whereas venlafaxine produces similar effects on both 5-HT and NE levels at the effective doses tested.

Comparison of the anticholinergic effects of the serotonergic antidepressants, paroxetine, fluvoxamine and clomipramine

Paroxetine, a selective serotonin reuptake inhibitor, shows relatively high affinity for muscarinic acetylcholine receptors compared to other selective serotonin reuptake inhibitors. To determine whether paroxetine has anticholinergic effects in vivo, we examined the effects of paroxetine on oxotremorine-induced tremor, spontaneous defecation and passive avoidance performance using mice and compared the results with those using fluvoxamine, another selective serotonin reuptake inhibitor, and clomipramine, a tricyclic antidepressant with serotonin selectivity. The potency of antidepressant activity as determined in the tail suspension test was paroxetine>fluvoxamine>clomipramine. Paroxetine and clomipramine inhibited oxotremorine-induced tremor, reduced spontaneous defecation and impaired passive avoidance performance, while fluvoxamine did not have similar effects. A comparison of ED(50) values showed that the ratio of anticholinergic effect to antidepressant activity was fluvoxamine, >3.2; paroxetine, 2.1-2.6; clomipramine, <0.8. These results suggest that paroxetine may induce fewer adverse anticholinergic effects than clomipramine, but more than fluvoxamine.

Serotonergic effects of clozapine and its metabolites in hippocampal HT22 cells

In the hippocampal neuronal in vitro system of HT22 cells, we studied the effects of clozapine (Cloz) and its metabolites clozapine-N-oxide (Cloz-N-oxide) and norclozapine (Norcloz) on 5-HT transporter affinity (K(M)) and uptake (V(max)), MAO-B affinity (K(M)) and maximal velocity (V(max)), as well as on 5-HT(2) receptor affinity and density. Clinically relevant concentrations of Cloz (200 and 400 ng/ml) and its metabolites (100 and 200 ng/ml) were used for the examination of the effects after short-term (4 h) and long-term (24 h) incubation. Statistical evaluation revealed that a significantly lowered 5-HT transporter affinity (higher K(M)) was related to higher concentrations of Cloz and its metabolites. A significantly higher 5-HT transporter uptake was dependent on both high concentrations of drugs and an increased time of incubation. No significant influence of the investigated independent variables on MAO-B affinity could be demonstrated, whereas a significant drug-related increase of MAO-B velocity was detectable. Additionally, low and high concentrations of Cloz and its metabolites induced a higher 5-HT(2) receptor affinity (lower K(D)). No significant influences of the investigated independent variables on 5-HT(2) receptor density were detectable. The results of the present study show that Cloz and its metabolites induce significant alterations in serotoninergic parameters of hippocampal HT22 cells, validating the system of hippocampal HT22 cells for further examinations of the mechanisms of action of atypical neuroleptics.

Discontinuation symptoms: comparison of brief interruption in fluoxetine and paroxetine treatment

Abrupt interruption or cessation of selective serotonin reuptake inhibitor (SSRI) treatment may result in discontinuation or treatment interruption symptoms. Recent reports suggested these symptoms occur more frequently with shorter half-life SSRIs. Previous studies indicated a 5-8-day treatment interruption resulted in fewer discontinuation-emergent adverse events in fluoxetine-treated patients than in paroxetine-treated patients. This study examines the effects of shorter treatment interruption (3-5 days), as would occur if patients miss just a few doses of medication. Patients successfully treated for depression with fluoxetine or paroxetine underwent treatment interruption in a double-blind fashion. Treatment interruption-emergent symptoms were assessed using the Discontinuation-Emergent Signs and Symptoms checklist. Other assessments included the Montgomery-Asberg Depression Rating Scale, Clinical Global Impressions-Severity scale and a social functioning questionnaire. Of 150 patients enrolled, 141 completed the study. Following treatment interruption, fluoxetine-treated patients experienced fewer treatment interruption-emergent events than did paroxetine-treated patients. The paroxetine treatment group also experienced significant increases in depressive symptoms, clinical global severity scores and difficulty in social functioning; the fluoxetine treatment group did not. These results are consistent with reports suggesting abrupt interruption of treatment with paroxetine is more often associated with somatic and psychological symptoms than is abrupt interruption of fluoxetine. Patients treated with fluoxetine appeared to be protected by its longer half-life.

Major depression with ischemic heart disease: effects of paroxetine and nortriptyline on long-term heart rate variability measures

BACKGROUND

Studies have linked depression to sudden death and serious cardiovascular events in patients with preexisting cardiac illness. Recent studies have shown decreased vagal function in cardiac patients with depression and depressed patients without cardiac illness.

METHODS

We compared 20-hour, sleeping, and awake heart period variability measures using spectral analysis, fractal dimension, and symbolic dynamics in two patient groups with major depression and ischemic heart disease (mean age 59-60 years) before and after 6 weeks of paroxetine or nortriptyline treatment.

RESULTS

Spectral measures showed decreases in awake and sleeping total power (TP: 0.0-0.5 Hz), ultra low frequency power (ULF: 0-0.0033 Hz), very low frequency power (VLF: 0.0033-0.04 Hz), and low-frequency power (LF: 0.04-0.15 Hz) for nortriptyline condition and a decrease in high-frequency power (HF: 0.15-0.5 Hz) for the awake condition in patients who received nortriptyline. A measure of nonlinear complexity, WC-100, significantly increased after paroxetine during the awake condition.

CONCLUSIONS

These findings suggest that nortriptyline has stronger vagolytic effects on cardiac autonomic function compared with paroxetine, which is in agreement with previous clinical and preclinical reports. Paroxetine may have some cardio-protective effects, especially in cardiac patients.

Paroxetine: an update of its use in psychiatric disorders in adults

Paroxetine is a selective serotonin reuptake inhibitor (SSRI), with antidepressant and anxiolytic activity. In 6- to 24-week well designed trials, oral paroxetine 10 to 50 mg/day was significantly more effective than placebo, at least as effective as tricyclic antidepressants (TCAs) and as effective as other SSRIs and other antidepressants in the treatment of major depressive disorder. Relapse or recurrence over 1 year after the initial response was significantly lower with paroxetine 10 to 50 mg/day than with placebo and similar to that with imipramine 50 to 275 mg/day. The efficacy of paroxetine 10 to 40 mg/day was similar to that of TCAs and fluoxetine 20 to 60 mg/day in 6- to 12-week trials in patients aged > or =60 years with major depression. Paroxetine 10 to 40 mg/day improved depressive symptoms to an extent similar to that of TCAs in patients with comorbid illness, and was more effective than placebo in the treatment of dysthymia and minor depression. Paroxetine 20 to 60 mg/day was more effective than placebo after 8 to 12 weeks' treatment of obsessive-compulsive disorder (OCD), panic disorder, social anxiety disorder (social phobia), generalised anxiety disorder (GAD) and post-traumatic stress disorder (PTSD). Improvement was maintained or relapse was prevented for 24 weeks to 1 year in patients with OCD, panic disorder, social anxiety disorder or GAD. The efficacy of paroxetine was similar to that of other SSRIs in patients with OCD and panic disorder and similar to that of imipramine but greater than that of 2'chlordesmethyldiazepam in patients with GAD. Paroxetine is generally well tolerated in adults, elderly individuals and patients with comorbid illness, with a tolerability profile similar to that of other SSRIs. The most common adverse events with paroxetine were nausea, sexual dysfunction, somnolence, asthenia, headache, constipation, dizziness, sweating, tremor and decreased appetite. In conclusion, paroxetine, in common with other SSRIs, is generally better tolerated than TCAs and is a first-line treatment option for major depressive disorder, dysthymia or minor depression. Like other SSRIs, paroxetine is also an appropriate first-line therapy for OCD, panic disorder, social anxiety disorder, GAD and PTSD. Notably, paroxetine is the only SSRI currently approved for the treatment of social anxiety disorder and GAD, which makes it the only drug of its class indicated for all five anxiety disorders in addition to major depressive disorder. Thus, given the high degree of psychiatric comorbidity of depression and anxiety, paroxetine is an important first-line option for the treatment of major depressive disorder, OCD, panic disorder, social anxiety disorder, GAD and PTSD.

Fluvoxamine: a review of its therapeutic potential in the management of anxiety disorders in children and adolescents

Fluvoxamine is a selective serotonin reuptake inhibitor (SSRI) which may be used for the management of anxiety disorders in children and adolescents. Absorption of fluvoxamine was similar in adolescents to that in adults, which suggests that the maximum dosage of the drug for patients aged between 12 and 17 years can be as high as 300 mg/day. However, steady-state plasma fluvoxamine [corrected] concentrations were 2 to 3 times higher in children (aged between 6 and 11 years) than in adolescents; thus, the maximum fluvoxamine dosage recommended for children is 200 mg/day. Fluvoxamine (50 to 300 mg/day) for 8 to 16 weeks significantly reduced symptoms of obsessive-compulsive disorder (OCD) [measured across multiple assessment scales] compared with placebo in a well controlled trial in paediatric patients (n = 120) or from baseline in noncomparative trials in adolescent (n = 20) or paediatric (n = 16) patients. Improvements with fluvoxamine (up to 200 mg/day) were observed for up to 1 year in 98 patients with OCD in a noncomparative trial. The drug (up to 250 or 300 mg/day) also improved symptoms of anxiety compared with placebo in an 8-week well controlled trial in 128 paediatric patients with social phobia, separation anxiety disorder or generalised anxiety disorder (GAD). Fluvoxamine (50 to 300 mg/day) appears to be well tolerated in paediatric patients, with most adverse events with the drug (except abdominal discomfort, which occurred more often in patients receiving fluvoxamine) occurring with a similar incidence to those with placebo. The most common adverse events involved the central nervous system or gastrointestinal system. Most adverse events reported by paediatric patients with OCD were similar to those reported by adults. In conclusion, fluvoxamine is generally well tolerated and has demonstrated short-term efficacy compared with placebo in the treatment of OCD, and social phobia, separation anxiety disorder or GAD in well controlled trials in paediatric patients. Reductions in symptoms of anxiety with fluvoxamine have been observed for up to 1 year in children and adolescents with OCD. However, there are currently no comparative trials of fluvoxamine with other pharmacological agents. In the absence of such trials, current consensus opinion recommends that when pharmacotherapy is indicated, fluvoxamine, like other SSRIs, can be used as first-line treatment for anxiety disorders, particularly OCD, in paediatric patients. However, direct comparisons are required to assess the relative efficacy and tolerability of pharmacological agents in order to make firm recommendations for the treatment of anxiety disorders in this patient group.

Pharmacological and behavioral analysis of the effects of some bivalent ligand-based monoamine reuptake inhibitors

Novel piperidine-based bivalent ligands were prepared in enantiomerically pure form and evaluated for their ability to inhibit reuptake of dopamine (DA), serotonin (5-HT), and norepinephrine (NE) into rat brain nerve endings (synaptosomes). In this study, we have succeeded in using (1) the length of the linking chain connecting the two piperidine-based monomer units and (2) the absolute configuration of the piperidine monomer as a means to tailor activity and selectivity at the three monoamine transporters tested. In this series, the bivalent ligand 16, comprised of two (+)-trans-piperidine units linked by a pentamethylene spacer, exhibits a combination of high DA transporter (DAT) and 5-HT transporter (SERT) activity (K(i) = 39 nM and 7 nM, respectively). Piperidine 16 is capable of reducing cocaine's locomotor effects in mice while not having any effect on locomotion when tested alone. Additionally, compound 16 (1-10 mg/kg) does not substitute for cocaine in drug discrimination studies in rats. However, the analogous bivalent ligand 15 comprised of two (-)-trans-piperidine units, which is SERT selective, was less effective in antagonizing cocaine's locomotor stimulant activity. The piperidine-based bivalent inhibitors described herein constitute a new class of monoamine reuptake inhibitors that exhibit varying levels of monoamine transporter activity and selectivity, and these ligands may serve as lead candidates in the discovery of new therapeutics to treat a range of neurological disorders including cocaine addiction.

Paroxetine: a review

Paroxetine is a potent and selective serotonin reuptake inhibitor (SSRI) with currently approved indications for the treatment of depression, obsessive-compulsive disorder, panic disorder and social phobia. It is also used in the treatment of generalized anxiety disorder, post traumatic stress disorder, premenstrual dysphoric disorder and chronic headache. Paroxetine, a phenylpiperidine derivative, is the most potent inhibitor of the reuptake of serotonin (5-hydroxytryptamine, 5-HT) of all the currently available antidepressants including the class of SSRIs. It is a very weak inhibitor of norepinephrine (NE) uptake but it is still more potent at this site than the other SSRIs. The selectivity of paroxetine, i.e., the ratio of inhibition of uptake of norepinephrine to serotonin (NE/5-HT) is amongst the highest of the SSRIs. Paroxetine has little affinity for catecholaminergic, dopaminergic or histaminergic systems and by comparison with tricyclic antidepressants (TCAs) has, therefore, a reduced propensity to cause central and autonomic side effects. Paroxetine exhibits some affinity for the muscarinic cholinergic receptor but much less than the TCAs. In addition, the adaptive changes of somatodendritic (5-HT(1A)) and terminal (5-HT(1B/1D)) autoreceptors observed with paroxetine are different to those observed with TCAs; it also inhibits nitric oxide synthase. It is both a substrate and an inhibitor of cytochrome isoenzyme P450 2D6. Paroxetine is well absorbed orally and undergoes extensive first pass metabolism that is partially saturable. Its metabolites are pharmacologically inactive in vivo. Steady state levels are achieved after 4-14 days and an elimination half-life of 21 h is consistent with once-daily dosing. There is wide inter-individual variation in the pharmacokinetics of paroxetine in adults as well as in the young and the elderly with higher plasma concentrations and slower elimination noted in the latter. Elimination is also reduced in severe renal and hepatic impairment. Serious adverse events are, however, extremely rare even in overdose. In summary, paroxetine is well tolerated and effective in the treatment of both depressive and anxiety disorders across the age range.

Sertraline versus paroxetine in major depression: clinical outcome after six months of continuous therapy

reuptake inhibitors (SSRIs) during continuation therapy. This investigation reports the differential effect of 6 months of treatment with sertraline versus paroxetine for symptoms of depression, quality of life, and personality outcomes. Outpatients with unipolar major depression (DSM-III-R) were randomly assigned to receive 24 weeks of double-blind treatment with flexible doses of paroxetine (20-40 mg) or sertraline (50-150 mg). Assessments included the Montgomery-Asberg Depression Rating Scale (MADRS), the Clinical Global Impression Scale, the Battelle Quality of Life Questionnaire, and the Structured Clinical Interview for DSM-III-R Personality Disorders screen questionnaire. One hundred seventy-six patients (mean age, 43 years; 64% female; baseline MADRS, 30.3) were treated with sertraline and 177 patients (mean age, 42 years; 71% female; MADRS, 30.7) with paroxetine. Antidepressant efficacy during continuation therapy was sustained, with only 2% of patients receiving sertraline and 9% of patients receiving paroxetine suffering a relapse. Continuation therapy resulted in a substantial conversion of responders during short-term treatment to full remission: remitter rates increased from 52% to 80% for sertraline and from 57% to 74% for paroxetine. The improvements in quality of life were related to a reduced depression score. SSRI treatment had significant beneficial effects on both categorical and dimensional measures of personality. A logistic regression analysis identified early response (25% reduction in MADRS scores at week 2) as the most important predictor of treatment response, whereas high severity, chronicity, and poor baseline quality of life had no effect. Both treatments were well-tolerated, with sertraline having a somewhat lower side effect profile. Sertraline and paroxetine demonstrated comparable efficacy during short-term and continuation therapy. Treatment was associated with significant improvement in quality of life and with reductions in axis II personality psychopathology.

Do antidepressants affect motivation in conditioned place preference?

The positive motivational effects of a range of antidepressants/neurotransmitter reuptake inhibitor compounds were studied using conditioned place preference. These agents included amitriptyline (2.5-10 mg/kg), venlafaxine (5 and 10 mg/kg), sibutramine (5 and 10 mg/kg), fluoxetine (2.5-10 mg/kg), paroxetine (5-15 mg/kg) and sertraline (2.5-10 mg/kg). Male Wistar rats were place conditioned in a three-compartment box to vehicle or drug alternately for 8 days using a 30-min pretreatment time. Control animals received vehicle only. Cocaine (5 mg/kg) was used as a positive control for the procedure. Significant place preference (P<0.05) was observed with paroxetine (15 mg/kg), fluoxetine (5 and 10 mg/kg), sertraline (2.5-10 mg/kg) and cocaine. Venlafaxine and sibutramine, serotonin/noradrenaline reuptake inhibitors, produced no place conditioning, while the highest dose of the tricyclic antidepressant, amitriptyline (10 mg/kg), produced signs of place aversion. The role of serotonin in reward pathways and differences in serotonin, noradrenaline and dopamine reuptake-inhibiting properties of these compounds may explain why only the serotonin-selective reuptake inhibitors produced place preference in this study.

Effect of a selective 5-hydroxytryptamine reuptake inhibitor on brain extracellular noradrenaline: microdialysis studies using paroxetine

The clinical efficacy of selective serotonin (5-hydroxytryptamine, 5-HT) reuptake inhibitors (SSRIs) is normally attributed to their ability to increase brain 5-HT function although recent preclinical findings indicate that their selectivity for 5-HT over noradrenaline may be less evident in vivo. The present study investigated the effects of the SSRI, paroxetine, on extracellular levels of noradrenaline. Microdialysis was carried out in the hippocampus of the awake rat. In rats treated twice daily for 14 days with paroxetine (5 mg/kg s.c.), dialysate levels of noradrenaline showed a maintained two-fold increase compared to saline-injected controls. Paroxetine (5 mg/kg s.c.) administered once daily for 14 days did not cause a sustained increase in noradrenaline but levels showed a moderate (+58%) increase in response to a paroxetine challenge. Acute injection of paroxetine (5 mg/kg s.c.) did not elevate noradrenaline levels. Paroxetine (5 mg/kg s.c.) elevated dialysate 5-HT after both acute and repeated (twice daily for 14 days) treatment. The paroxetine-induced increase in noradrenaline (and 5-HT) was positively correlated with plasma concentrations of the drug, which were around the therapeutic range. In comparison to paroxetine, desipramine (10 mg/kg s.c.) caused a four-fold increase in dialysate noradrenaline (but did not change 5-HT) following repeated (once daily for 14 days) treatment and a two-fold increase at for acute treatment. In summary, despite its selectivity as a 5-HT reuptake inhibitor, paroxetine increased extracellular levels of noradrenaline in rat hippocampus following repeated administration. We discuss the possibility that a facilitation of noradrenaline function might be involved in the antidepressant effect of paroxetine, and possibly other SSRIs.

Fluvoxamine. An updated review of its use in the management of adults with anxiety disorders

Fluvoxamine is a potent and selective serotonin reuptake inhibitor (SSRI) that has little or no effect on other monoamine reuptake mechanisms. Relative to other SSRIs, fluvoxamine is a weak inhibitor of cytochrome P450 (CYP) 2D6, a moderate inhibitor of CYP2C19 and CYP3A4 and a potent inhibitor of CYP1A2. In randomised, double-blind trials. fluvoxamine 100 to 300 mg/day for 6 to 10 weeks significantly reduced symptoms of obsessive-compulsive disorder (OCD) compared with placebo. Response rates of 38 to 52% have been reported with fluvoxamine, compared with response rates of 0 to 18% with placebo. In patients with OCD, fluvoxamine had similar efficacy to that of clomipramine and, in smaller trials, the SSRIs paroxetine and citalopram and was significantly more effective than desipramine. Maintenance therapy with fluvoxamine may reduce the likelihood of relapses in up to 67% of patients with OCD. Fluvoxamine < or = 300 mg/day for 6 to 8 weeks was as effective as imipramine in patients with panic disorder, and significantly more effective than placebo. In addition, treatment with fluvoxamine < or = 300 mg/day for > or = 8 weeks improved symptoms of social phobia (social anxiety disorder), post-traumatic stress disorder (PTSD), pathological gambling, compulsive buying, trichotillomania, kleptomania, body dysmorphic disorder, eating disorders and autistic disorder. Large trials comparing the efficacy of fluvoxamine and other SSRIs in patients with anxiety disorders are warranted. Fluvoxamine is generally well tolerated; in postmarketing studies, nausea was the only adverse event occurring in >10% of patients with less commonly reported events including somnolence, asthenia, headache, dry mouth and insomnia. Fluvoxamine is associated with a low risk of suicidal behaviour, sexual dysfunction and withdrawal syndrome. Fewer anticholinergic or cardiovascular events are associated with fluvoxamine than tricyclic antidepressants. Although comparative data are lacking, the tolerability profile of fluvoxamine appears to be broadly similar to those of other SSRIs.

CONCLUSION

Fluvoxamine has demonstrated short term efficacy in the treatment of OCD, panic disorder, social phobia, PTSD and in a range of obsessive-compulsive spectrum disorders. The drug is as effective as clomipramine in patients with OCD but appears to have a better tolerability profile. On the basis of current treatment guidelines, fluvoxamine, like other SSRIs, is recommended as first-line treatment for a number of anxiety disorders. It appears to offer some pharmacokinetic advantages and a different drug interaction profile to the other SSRIs with a broadly similar spectrum of adverse events. However, direct comparisons are required to assess the relative efficacy and tolerability of the different agents of this drug class.

The SSRI discontinuation syndrome

A characteristic selective serotonin reuptake inhibitor (SSRI) discontinuation syndrome appears to exist. It is usually mild, commences within 1 week of stopping treatment, resolves spontaneously within 3 weeks, and consists of diverse physical and psychological symptoms, the commonest being dizziness, nausea, lethargy and headache. SSRI reinstatement leads to resolution within 48 h. A transient stage of serotonin dysregulation appears central to causation with pharmacokinetic and pharmacodynamic differences accounting for the variation in incidence between the SSRIs. Discontinuation reactions are clinically relevant due to the associated morbidity, the potential for misdiagnosis and inappropriate treatment and because they may impair future antidepressant compliance. To minimize incidence, SSRIs, like other antidepressants, should be withdrawn gradually. Provisional diagnostic criteria for the SSRI discontinuation syndrome are proposed. Prospective studies are required to investigate the syndrome, particularly its effects on patient care.

Effects of acute and chronic tianeptine administration on serotonin outflow in rats: comparison with paroxetine by using in vivo microdialysis

Using in vivo microdialysis, we compared the effects of tianeptine (an antidepressant drug which, in marked contrast with other antidepressants, is thought to increase the uptake of serotonin (5-hydroxytryptamine, 5-HT) on extracellular 5-HT concentrations ([5-HT](ext)) in the frontal cortex and raphe nuclei of freely moving rats with those of paroxetine, a potent selective serotonin reuptake inhibitor. A single paroxetine dose (1 mg/kg, i.p.) increased [5-HT](ext) over baseline in the frontal cortex and raphe nuclei, respectively. A single administration of tianeptine (10 mg/kg, i.p.) did not change [5-HT(ext)] in the two brain regions studied. Repeated exposure to paroxetine (0.5 mg/kg) b.i.d. for 14 days induced a sixfold significant increase in basal [5-HT](ext) in the raphe nuclei. Administration of tianeptine (5 mg/kg) b.i.d. for 14 days did not affect 5-HT baseline concentrations. In rats chronically treated with either paroxetine or tianeptine, drug challenge did not alter area under the curve values. Thus, our in vivo data indicate that tianeptine and paroxetine do not exert a similar in vivo effect on the serotonergic system in rat brain.

Latency to paroxetine-induced anxiolysis in the rat is reduced by co-administration of the 5-HT(1A) receptor antagonist WAY100635

We report here the use of rat high-light social interaction to model the temporal anxiolytic/antidepressant effects of SSRIs seen in the clinic. Compared to vehicle controls, 21, but not 14, days of paroxetine treatment (3 mg kg(-1), p.o., daily) produced a marked increase in rat social interaction (Vehicle=71.3+/-7.3 s; Paroxetine=116.7+/-14.7 s; P<0.01) with no concurrent effect on locomotor activity, consistent with anxiolysis. To assess whether concurrent 5-HT(1A) receptor blockade reduces the time to onset of anxiolysis seen with paroxetine alone (21 days), rats were implanted with osmotic minipumps to continuously infuse the 5-HT(1A) receptor antagonist WAY100635 (1 mg kg(-1) day(-1), s.c., 7 days) alone or in combination with paroxetine (3 mg kg(-1), p.o., daily, 7 days), prior to anxiety testing. Paroxetine (Veh/Par=61.9+/-7.9 s) or WAY100635 (WAY/Veh=71.6+/-4.7 s) alone, had no effect on social interaction time compared to vehicle treated controls (Veh/Veh=76.4+/-4.9 s), whilst coadministration of WAY100635 with paroxetine, produced a marked elevation in social interaction (WAY/Par=149.3+/-16.8 s; P<0.01) relative to all other groups with no concurrent change in locomotor activity. In contrast, acute administration of WAY100635 (0.03 mg kg(-1), s.c.) with paroxetine (3 mg kg(-1), p.o.) did not alter any behavioural measure, suggesting that the anxiolysis induced by the combination after 7 days is attributable to a CNS adaptive response. This data demonstrates that coadministration of a 5-HT(1A) receptor antagonist with paroxetine markedly reduces the latency to anxiolysis, in the rat. This study supports the use of the rat social interaction test to further delineate adaptive changes in the CNS responsible for the anxiolytic/antidepressant action of SSRIs seen in humans.

Homeostatic regulation of serotonergic function by the serotonin transporter as revealed by nonviral gene transfer

With the aim of exploring the relationship between the serotonin transporter (5-HTT or SERT) and the activity level of serotonin (5-HT) neurotransmission, in vivo expression of this protein was specifically altered using a nonviral DNA transfer method. Plasmids containing the entire coding sequence or a partial antisense sequence of the 5-HTT gene were complexed with the cationic polymer polyethylenimine and injected into the dorsal raphe nucleus of adult male rats. Significant increase or decrease in both [(3)H]citalopram binding and [(3)H]5-HT synaptosomal uptake were observed in various brain areas up to 2 weeks after a single administration of the sense plasmid or 7 d after injection of the short antisense plasmid, respectively. Such changes in 5-HTT expression were associated with functional alterations in 5-HT neurotransmission, as shown by the increased capacity of 5-HT(1A) receptor stimulation to enhance [(35)S]GTP-gamma-S binding onto the dorsal raphe nucleus in sections from rats injected with the sense plasmid. Conversely, both a decrease in 5-HT(1A)-mediated [(35)S]GTP-gamma-S binding and a reduced potency of the 5-HT(1A) receptor agonist ipsapirone to inhibit neuronal firing were observed in the dorsal raphe nucleus of antisense plasmid-injected rats. Furthermore, changes in brain 5-HT and/or 5-HIAA levels, and sleep wakefulness circadian rhythm in the latter animals demonstrated that altered expression of 5-HTT by recombinant plasmids has important functional consequences on central 5-HT neurotransmission in adult rats.

Effects of subchronic paroxetine administration on night-time endocrinological profiles in healthy male volunteers

To evaluate the subchronic effects of paroxetine, a selective serotonin reuptake inhibitor, on nocturnal endocrinological profiles, eight healthy male volunteers with no personal or family history of a psychiatric or neurological disease were administered paroxetine (30 mg/day) or placebo in a double-blind cross-over design. Drugs were given as a single dose at 10:00 h for a period of 4 weeks each. Between days 21 and 28 of each treatment period, sleep EEG was registered for four consecutive nights from 23:00 to 07:00 h. During the last night, hormonal profiles for prolactin, growth hormone (GH), cortisol, corticotropin (ACTH), luteinizing hormone (LH), testosterone and melatonin were determined, and area-under-the-curve values were calculated. None of the endocrinological parameters revealed any statistically significant changes. A trend could be found for an increased cortisol production under paroxetine (P = 0.069). ACTH, LH, and melatonin showed slight and non-significant decreases. Prolactin release was only marginally elevated (+7%). The mean sleep onset GH release (as measured for a time period of 180 min after sleep onset) was decreased by about 30% under paroxetine. However, statistical significance could not be reached. For hGH, there was a delayed mean GH-peak under paroxetine. Nocturnal testosterone secretion remained almost unaltered. The lack of significant endocrinological alterations might be partially explained by both adaptational phenomena under subchronic treatment conditions and the extended time span between the single morning dose and the registration period, respectively.

Reboxetine: a pharmacologically potent, selective, and specific norepinephrine reuptake inhibitor

BACKGROUND

Reboxetine is a potent antidepressant, with efficacy comparable to that of imipramine, desipramine, and fluoxetine, and has improved side-effect profile. The basis of its efficacy and improved tolerability is sought through studies of reboxetine in a number of pharmacological models of depression.

METHODS

Pharmacological selectivity for uptake systems was defined by uptake and binding assays for the three monoamine uptake sites. Specificity was determined in 39 different receptor and 6 enzyme assays. In vivo selectivity was defined by measurement of neuronal firing rates in the locus coeruleus, dorsal raphe, and substantia nigra. Reserpine-induced blepharospasm and hypothermia, clonidine-induced hypothermia, defined reboxetine's in vivo pharmacology. Reboxetine's antidepressant potential was evaluated behaviorally by the tail-suspension test, forced swimming, and the DRL72 operant responding test.

RESULTS

Reboxetine is a potent, selective, and specific norepinephrine reuptake inhibitor (selective NRI) as determined by both in vitro and in vivo measurements. Unlike desipramine or imipramine, reboxetine has weak affinity (Ki > 1,000 nmol/L)for muscarinic, histaminergic H1, adrenergic alpha1, and dopaminergic D2 receptors. In vivo action of reboxetine is entirely consistent with the pharmacological action of an antidepressant with preferential action at the norepinephrine reuptake site. Reboxetine showed an antidepressant profile in all tests of antidepressant activity used. Significant decreases in immobility were observed in the tail suspension test and behavioral despair test. Increased efficiency in responding was observed in the DRL72 test.

CONCLUSIONS

Reboxetine is a potent, selective, and specific noradrenergic reuptake inhibitor. It has a superior pharmacological selectivity to existing tricyclic antidepressants and selective serotonin reuptake inhibitors when tested in a large number of in vitro and in vivo systems. Given the pharmacological profile, reboxetine is expected to be a selective and potent tool for psychopharmacological research. The use of reboxetine in the clinic will also help clarify the role norepinephrine plays in depression.

Further SAR studies of piperidine-based analogues of cocaine. 2. Potent dopamine and serotonin reuptake inhibitors

The synthesis and monoamine transporter activity of additional members of a series of 3,4-disubstituted piperidines (truncated analogues of the WIN series) are described. All members of this series were prepared from arecoline hydrobromide in optically pure form and were evaluated for their ability to inhibit high affinity uptake of dopamine (DA), serotonin (5-HT) and norepinephrine (NE) into rat brain nerve endings (synaptosomes). Most of the compounds prepared in this series are reasonably potent DAT inhibitors (K(i) values of 4-400 nM) and have selectivity for the 5-HT transporter relative to both the NE transporter (3-9-fold) and to the DAT ( approximately 25-fold). In the present series, (-)-methyl 1-methyl-4beta-(2-naphthyl)piperidine-3beta-carboxylate (6) was found to be the most potent piperidine-based ligand, exhibiting K(i)'s of 21 nM and 7.6 nM at the DAT and 5-HTT, respectively. While the 5-HTT activity of compound 6 is comparable to that of the antidepressant medication fluoxetine, it is less selective. As is apparent from the data presented, the naphthyl substituted piperidines 6-9, which differ in their stereochemistry, show different degrees of selectivity for the three transporters. Consistent with results reported in the literature for the tropane analogues, removal of the methyl group from the nitrogen atom of 9 leads to a further enhancement in 5-HTT activity. To examine the in vivo effects of these piperidines, preliminary behavioral screening was carried out on piperidine 14. Despite its 2.5-fold greater DAT activity compared to cocaine, piperidine 14 was found to be about 2. 5-fold less potent in increasing distance traveled in mice. However, consistent with its DAT activity, piperidine 14 was found to be about 2.5-fold more potent than cocaine in enhancing stereotypic movements. Further studies of these piperidine-based ligands may provide valuable insights into the pharmacological mechanisms underlying the enhancement in distance traveled versus stereotypic movements. The present results have important implications for better understanding the structural motifs required in the design of agents with specific potency and selectivity at monoamine transporters.

The acute effects of monoamine reuptake inhibitors on the stimulus effects of hallucinogens

In a previous study it was observed that fluoxetine potentiates the stimulus effects of lysergic acid diethylamide (LSD). In the present investigation, stimulus control was established in groups of rats using as training drugs the hallucinogens lysergic acid diethylamide (LSD); 0.1 mg/kg), (-)-2,5-dimethoxy-4-methylamphetamine [(-)-DOM; 0.56 mg/kg], ibogaine (10 mg/kg), and 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT; 3 mg/kg). A two-lever, fixed-ratio 10, positively reinforced task with saline controls was employed. The hypotheses tested were that (a) monoamine uptake inhibitors other than fluoxetine potentiate the discriminative effects of LSD, and (b) hallucinogens other than LSD are potentiated by acute pretreatment with monoamine uptake inhibitors. The effects of a range of doses of each of the training drugs were determined both alone and following pretreatment with the monoamine reuptake inhibitors fluoxetine, fluvoxamine, and venlafaxine. In LSD-trained subjects, all three reuptake inhibitors caused a significant increase in LSD-appropriate responding. Similar results were observed in rats trained with (-)-DOM and with ibogaine. In 5-MeO-DMT-trained subjects, only fluoxetine resulted in an enhancement of drug-appropriate responding. The reuptake inhibitors given alone elicited varying degrees of responses appropriate for the respective training drugs. For fluoxetine in rats trained with LSD and ibogaine, for venlafaxine in LSD trained, and for fluvoxamine in (-)-DOM trained, the degree of responding met our criterion for intermediate responding, i.e., significantly different from both training conditions. Subsequent experiments in (-)-DOM-trained subjects examined a range of doses of each of the reuptake inhibitors in combination with a fixed dose of (-)-DOM (0.1 mg/kg), which alone yielded about 50% (-)-DOM-appropriate responding. With the exception of the point obtained with the highest dose of venlafaxine, all data were compatible with additivity of effects rather than true potentiation. In summary, the present data extend our previous observation of the augmentation of the stimulus effects of LSD by fluoxetine to include other hallucinogens. The mechanisms by which these interactions arise and possible differential effects of acute and chronic treatment remain to be established.

A Canadian multicenter, double-blind study of paroxetine and fluoxetine in major depressive disorder

BACKGROUND

Recent studies have suggested clinical differences among selective serotonin reuptake inhibitors. In a 12-week randomized, multicenter, double-blind trial, the antidepressant and anxiolytic efficacy of the selective serotonin reuptake inhibitors paroxetine and fluoxetine was compared in patients with moderate to severe depression.

METHODS

A total of 203 patients were randomized to fixed doses (20 mg/day) of paroxetine or fluoxetine for the first six weeks of therapy. From week 7-12, dosing could be adjusted biweekly, as required (paroxetine 20-50 mg/day, and fluoxetine 20-80 mg/day). The mean prescribed doses were paroxetine 25.5 mg/day (range 20.0-40.2 mg/day), and fluoxetine 27.5 mg/day (range 20.0-59.5 mg/day). Emergence of motor nervousness or restlessness was assessed using the ESRS scale for akathisia.

RESULTS

Both active treatments demonstrated comparable antidepressant efficacy (HAM-D, CGI). Anxiolytic activity of the two drugs (COVI, STAI, HAM-D) was also comparable. However, paroxetine was found to be superior to fluoxetine on two subscore measures at week 1 of therapy (HAM-D Agitation item, p < 0.05; Psychic Anxiety item, p < 0.05), with no differences detected after week 2. The overall incidence of adverse effects was comparable in the two treatment groups. Constipation, dyspepsia, tremor, sweating and abnormal ejaculation were more common in paroxetine-treated subjects, whereas nausea and nervousness were more frequent in fluoxetine-treated patients. Weight loss was more common in the fluoxetine versus paroxetine group (11.88% versus 2.94%, respectively). ESRS scores for akathisia were low throughout the study and showed little change.

LIMITATIONS

Differences observed between the two drugs in antianxiety effects were limited to two measures of anxiety among several others.

DISCUSSION

The data indicate that paroxetine and fluoxetine have comparable antidepressant and anxiolytic efficacy. Paroxetine appears to produce an earlier improvement in agitation and psychic anxiety symptoms compared with fluoxetine.

Venlafaxine: discrepancy between in vivo 5-HT and NE reuptake blockade and affinity for reuptake sites

Using an in vivo electrophysiological paradigm, venlafaxine and paroxetine displayed similar potency for suppressing the firing activity of dorsal raphe 5-HT neurons (ED50: 233 and 211 microg/kg i.v., respectively), while venlafaxine was three times less potent than desipramine (ED50: 727 and 241 microg/kg i.v., respectively) to suppress the firing activity of locus coeruleus NE neurons. The selective 5-HT1A receptor antagonist WAY 100635 (100 microg/kg, i.v.) reversed the suppressant effect of venlafaxine and paroxetine on the firing activity of 5-HT neurons and the alpha2-adrenoceptor antagonist piperoxane (1 mg/kg, i.v.) reversed those of venlafaxine and desipramine on the firing activity of NE neurons. The ED50 of venlafaxine on the firing activity of 5-HT neurons was not altered (ED50: 264 microg/kg) in noradrenergic-lesioned rats, while the suppressant effect of venlafaxine on the firing activity of NE neurons was greater in serotonergic-lesioned rats (ED50: 285 microg/kg). Taken together, these results suggest that, in vivo, venlafaxine blocks both reuptake processes, its potency to block the 5-HT reuptake process being greater than that for NE. Since the affinities of venlafaxine for the 5-HT and NE reuptake carriers are not in keeping with its potencies for suppressing the firing activity of 5-HT and NE neurons, the suppressant effect of venlafaxine on the firing activity of 5-HT and NE neurons observed in vivo may not be mediated solely by its action on the [3H]cyanoimipramine and [3H]nisoxetine binding sites. In an attempt to unravel the mechanism responsible for this peculiarity, in vitro superfusion experiments were carried out in rat brain slices to assess a putative monoamine releasing property for venlafaxine. (+/-)Fenfluramine and tyramine substantially increased the spontaneous outflow of [3H]5-HT and [3H]NE, respectively, while venlafaxine was devoid of such releasing properties.

Psychopharmacological profile of the selective serotonin reuptake inhibitor, paroxetine: implication of noradrenergic and serotonergic mechanisms

The present study was designed to evaluate the psychopharmacological profile of the selective serotonin reuptake inhibitor paroxetine, and thus assess potential noradrenergic and/or serotonergic activity. Paroxetine dose-dependently increased mobility time in the mouse forced swimming test (8, 16, 32 and 64 mg/kg, i.p.) and reduced spontaneous locomotor activity when administered at a high dose (64 mg/kg, i.p.). Prior administration of 8-hydroxy-2-(di-n-propylamino)tetralin (1 mg/kg, i.p.), (+/-) pindolol (32 mg/kg, i.p.) or 5-methoxy-3-(1,2,3,6-tetrahydro-4-pyridyl)-1H-indole (RU 24969) (1 mg/kg, i.p.) potentiated the antidepressant-like effects of subactive doses of paroxetine (1, 2 and 4 mg/kg, i.p.) in the mouse forced swimming test. These effects were antagonized by prior administration of 1-(2-methoxyphenyl)-4-[-(2-phthalimido)butyl]piperazine) (0.5 mg/kg, i.p.). Complementary studies suggested that RU24969-induced anti-immobility effects were a result of an increase in locomotor activity; other interactions were without increase/decrease in locomotor activity. Acute administration of paroxetine (8, 16, and 32 mg/kg, i.p.) antagonized the hypothermia induced by the D2/D1 receptor agonist, apomorphine (16 mg/kg, s.c.), while repeated treatment with paroxetine (32 mg/kg) attenuated clonidine-induced (0.5 mg/kg, i.p.) hypothermia. Pre-treatment with the serotonergic neurotoxin, para-chlorophenylalanine attenuated the anti-immobility effects of low doses of paroxetine (8 and 16 mg/kg, i.p.) in the forced swimming test, whereas a higher dose of paroxetine remained active (32 mg/kg, i.p.). The results of the present study indicated that paroxetine displayed both noradrenergic-like and serotonergic-like activity in the pre-clinical psychopharmacological tests employed.

Conventional and spectral power analysis of all-night sleep EEG after subchronic treatment with paroxetine in healthy male volunteers

Paroxetine is a selective and potent serotonin reuptake inhibitor with reported antidepressant properties. Since changes in the regular sleeping pattern were described as side effects under treatment with paroxetine, the impact of the drug on the sleep architecture is of major interest. The present study addressed the question of subchronic effects of paroxetine medication (30 mg/day) in eight healthy male volunteers in a double blind, placebo-controlled crossover-design. Conventional sleep EEG parameters and additionally computed spectral power analysis based on FFT of 20-s time epochs in the delta, theta, alpha, beta and gamma frequency range for different sleep stages after 4 weeks of treatment were investigated. Subchronic paroxetine administration in healthy subjects led to a prolonged REM latency and a decrease in the number of REM phases, whereas sleep efficiency, total sleep time, sleep onset latency, number of awakenings, and awake during sleep period time were not altered by paroxetine medication. Moreover, we could not detect any alterations of the spectral power values in certain frequency bands during NREM or REM sleep following subchronic paroxetine medication.

Sibutramine. A review of its contribution to the management of obesity

Sibutramine is an orally administered centrally acting weight management agent apparently devoid of amphetamine-like abuse potential. Its primary (M2; BTS 54,505) and secondary (M1; BTS 54,354) amine metabolites are pharmacologically active and are thought to induce the natural processes leading to enhancement of satiety and thermogenesis by inhibiting serotonin (5-hydroxytryptamine, 5-HT) and noradrenaline (norepinephrine) reuptake. In clinical trials, once-daily sibutramine was administered at dosages of < or = 30 mg for < or = 24 weeks and 10 or 15 mg for 1 year in conjunction with reduced calorie intake, increased daily exercise and advice on eating behaviour. Dose-related bodyweight loss was greater with sibutramine than with placebo. Clinical effects were most commonly apparent at dosages > or = 10 mg/day. Weight loss of > 1% within the first month of treatment appears indicative of good long term response with sibutramine. Weight loss was maintained during therapy for 1 year; longer term data are lacking. Weight regain occurred after treatment cessation in studies of < or = 24 weeks' duration; data from longer trials are unavailable. Up to 15% of patients in < or = 6-month studies did not respond to treatment irrespective of dose. Obese patients with type 2 (non-insulin-dependent) diabetes or hypertension lost significantly more mean bodyweight with sibutramine than with placebo, although weight loss was less than that in obese patients without comorbidities. The effect of sibutramine on mean fasting blood glucose levels and plasma lipid levels was unclear. Sibutramine, compared with placebo, statistically significantly increased blood pressure and heart rate in obese patients with or without hypertension when given for up to 12 months. However, after 12 weeks' treatment in hypertensive obese patients, diastolic blood pressure was reduced by similar amounts with sibutramine or placebo. Concerns over potential pressor effects with sibutramine are reflected in the manufacturer's dosage and administration recommendations.

SSRI-induced extrapyramidal side-effects and akathisia: implications for treatment

The selective serotonin reuptake inhibitors (SSRIs) may occasionally induce extrapyramidal side-effects (EPS) and/or akathisia. This may be a consequence of serotonergically-mediated inhibition of the dopaminergic system. Manifestations of these effects in patients may depend on predisposing factors such as the presence of psychomotor disturbance, a previous history of drug-induced akathisia and/or EPS, concurrent antidopaminergic and/or serotonergic therapy, recent monoamine oxidase inhibitor discontinuation, comorbid Parkinson's disease and possibly deficient cytochrome P450 (CYP) isoenzyme status. There is increasing awareness that there may be a distinct form of melancholic or endogenous depression with neurobiological underpinnings similar to those of disorders of the basal ganglia such as Parkinson's disease. Thus, it is not surprising that some individuals with depressive disorders appear to be susceptible to developing drug-induced EPS and/or akathisia. In addition, the propensity for the SSRIs to induce these effects in individual patients may vary within the drug class depending, for example, on their selectivity for serotonin relative to other monoamines, affinity for the 5-HT2C receptor, pharmacokinetic drug interaction potential with concomitantly administered neuroleptics and potential for accumulation due to a long half-life. The relative risk of EPS and akathisia associated with SSRIs have yet to be clearly established. The potential risks may be reduced by avoiding rapid and unnecessary dose titration. Furthermore, early recognition and appropriate management of EPS and/or akathisia is required to prevent the impact of these effects on patient compliance and subjective well-being. It is important that the rare occurrence of EPS in patients receiving SSRIs does not preclude their use in Parkinson's disease where their potentially significant role requires more systematic evaluation.

Investigation of the presynaptic effects of quinine and quinidine on the release and uptake of monoamines in rat brain tissue

Quinine and quinidine are reported to potentiate the behavioural effects of serotonergic agents and monoamine uptake inhibitors. We have therefore investigated the presynaptic actions of quinine and quinidine on monoamine uptake and release in rat brain tissue in vitro. Quinidine evoked the release of [3H]5-HT, [3H]noradrenaline and [3H]dopamine from pre-loaded rat brain slices in a concentration dependent manner with EC50 values of 175, 486 and 150 microM, respectively. Quinine induced [3H]monoamine release with similar potencies. Both quinine and quinidine also inhibited the active uptake of [3H]5-HT, [3H]noradrenaline and [3H]dopamine into rat brain synaptosomes with IC50 values in the range 0.13-12.4 microM. The potency of each drug to inhibit [3H]5-HT uptake was significantly higher than that for [3H]noradrenaline or [3H]dopamine. The relative potency of quinidine compared to quinine was more marked in the case of [3H]5-HT (58-fold) than for [3H]noradrenaline (3-fold) or [3H]dopamine (4-fold). The inhibition of [3H]5-HT uptake by quinine and quinidine was competitive in nature and corresponded with the potencies of these drugs to inhibit [3H]paroxetine binding. No correlation was observed between the potencies of quinine and quinidine to induce the release of [3H]monoamines and to inhibit their uptake, suggesting that these effects are mediated by two distinct mechanisms. We conclude that the presynaptic actions of quinine and quinidine on monoamine uptake and release may be implicated in their potentiation of the effects of serotonergic agents and uptake blockers.

Serotonin transporters in adult rat brain astrocytes revealed by [3H]5-HT uptake into glial plasmalemmal vesicles

Cultured astrocytes derived from neonatal rat brain exhibited high affinity, Na+-dependent, paroxetine and fluoxetine sensitive [3H]5-HT uptake. Reverse transcriptase-PCR demonstrated that astrocytes in culture expressed messenger RNA for the cloned serotonin transporter protein which has been characterised as the neuronal serotonin transporter. Although the serotonin transporter in cultured astrocytes displayed a Km value approximately 10 times greater than found in adult brain synaptosomes, these observations indicated that astrocytes in vitro may express the same serotonin transporter as neurons. Reverse transcriptase-PCR demonstrated the presence of serotonin transporter mRNA in the adult rat cerebral cortex, suggesting that astrocytes in vivo may express low levels of this mRNA. To investigate whether astrocytes in the adult CNS express functional serotonin transporters, glial plasmalemmal vesicles were prepared from cerebral cortex, representing a subcellular fraction composed primarily of vesicles derived from astrocytes. These vesicles were characterised by [3H]-glutamate and [3H]-dopamine uptake and by immunoblot analysis, using glial and synaptic markers: glutamate synthase, SNAP-25 and synaptobrevin. [3H]5-HT was taken up into glial plasmalemmal vesicles in a high affinity (Km approximately 40 nM), Na+ dependent, paroxetine-sensitive manner. The [3H]5-HT uptake capacity (Vmax) in these vesicles was approximately one quarter of that observed in synaptosomes. These data indicate that astrocytes in culture and in vivo are capable of 5-HT uptake via the previously characterised 'neuronal' serotonin transporter.

Treatment of behavioural disturbances in Parkinson's disease

Behavioural disorders in Parkinson's disease can grossly be subdivided in primary disturbances and those which are related to drug treatment. Depression and anxiety are a common feature in parkinsonian patients. Both occur independently of drug treatment. In general, most current antidepressive and anxiolytic drugs could be administered in Parkinson's disease with the same precautions as in the normal population. However, in single case reports modern serotonin reuptake blockers in Parkinson's disease have been accused to worsen parkinsonian motor condition. Combinations of serotonin reuptake inhibitors with MAO-inhibitors like selegiline should be used with caution. In the case of cognitive decline firstly an underlying depression should be disclosed or if existent be treated. Depression seems to be the single most important factor associated with the severity of dementia and early antidepressant treatment seems to decrease cognitive decline in depressed parkinsonian patients. Anticholinergic medications should be discontinued since they may cause mental side effects. Sleep disorders in Parkinson's disease are mainly caused by nocturnal akinesia, which causes sleep fragmentation or altered dreaming and nightmares, which might be a side-effect of dopaminergic treatment. In the first case the administration of a controlled release preparation of levodopa at bedtime may be indicated. If the sleep disorder is considered to be due to dopaminergic medication, a reduction of long-term acting agents like modern dopamine agonists and controlled-release levodopa should be considered. In severe psychotic states related to drug treatment antiparkinsonian therapy must be carefully analysed and, if possible, reduced. If motor condition worsens and/or psychiatric symptoms do not improve, initiation with "atypical" neuroleptics like clozapine is indicated. The pharmacological and clinical properties of new antipsychotic drugs that can be used in Parkinson's disease are revised.

Evaluation of efficacies of different classes of antidepressants in the forced swimming test in mice at different ages

1. The efficacies of different classes of antidepressants were investigated using the forced swimming test with mice at different ages. 2. Imipramine (4-32 mg/kg), desipramine (2-16 mg/kg) and bupropion (32, 64 mg/kg) showed activity in all age groups. 3. The selective serotonin reuptake inhibitors (SSRIs) citalopram (16 and 32 mg) and paroxetine (4 and 8 mg) were inactive in the oldest (40 weeks) group of mice, despite showing activity at the same doses in mice ranging in age from 4-24 weeks old. 4. Both SSRIs showed anti-immobility effects at low doses, (paroxetine: 1 and 2 mg/kg; citalopram: 4 and 8 mg/kg) in the 40-week old mice. These effects were not evident in the three younger groups of mice. 5. Moclobemide, a reversible selective inhibitor of monoamine oxidase-A, showed activity only at a high dose (128 mg/kg) and only in 12-week old animals. 6. Since SSRIs have been reported to have relatively selective effects on 5-HT1B receptors, the present results suggest that further studies comparing the effectiveness of SSRIs and other antidepressants in elderly patients should be done. Studies of the effects of aging on the density and/or affinity of 5-HT1A and 5-HT1B/1D receptors are also warranted.

Paroxetine. An update of its pharmacology and therapeutic use in depression and a review of its use in other disorders

Paroxetine is a potent and selective inhibitor of the neuronal reuptake of serotonin (5-hydroxytryptamine; 5-HT), which was previously reviewed as an antidepressant in Drugs in 1991. Since then, more comparative trials with other antidepressants have become available, and its use in the elderly and as long term maintenance therapy has been investigated. Paroxetine has also been studied in several other disorders with a presumed serotonergic component, primarily obsessive compulsive disorder (OCD) and panic disorder. In short term clinical trials in patients with depression, paroxetine produced clinical improvements that were significantly greater than those with placebo and similar to those achieved with other agents including tricyclic antidepressants (TCAs), maprotiline, nefazodone and the selective serotonin reuptake inhibitors (SSRIs) fluoxetine, fluvoxamine and sertraline. Long term data suggest that paroxetine is effective in preventing relapse or recurrence of depression in patients treated for up to 1 year. In the elderly, the overall efficacy of paroxetine was at least as good as that of comparator agents. In short term clinical trials involving patients with OCD or panic disorder, paroxetine was significantly more effective than placebo and of similar efficacy to clomipramine. Limited long term data show that paroxetine is effective in maintaining a therapeutic response over periods of 1 year (OCD) and up to 6 months (panic disorder). Preliminary data suggest that paroxetine has potential in the treatment of social phobia, premenstrual dysphoric disorder and chronic headache. Like the other SSRIs, paroxetine is better tolerated than the TCAs, causing few anticholinergic adverse effects. The most commonly reported adverse event associated with paroxetine treatment is nausea, although this is generally mild and subsides with continued use. Fewer withdrawals from treatment due to adverse effects occurred with paroxetine treatment than with TCAs. The adverse events profile of paroxetine appears to be broadly similar to that of other SSRIs, although data from comparative trials are limited. Serious adverse effects associated with paroxetine are very rare. In conclusion, paroxetine is effective and well tolerated, and suitable as first-line therapy for depression. It also appears to be a useful alternative to other available agents for the treatment of patients with OCD or panic disorder.

Breast enlargement during chronic antidepressant therapy

Recent reports of mammoplasia during selective serotonin re-uptake inhibitor (SSRI) therapy suggested that this side effect may be more common than previously reported. We examined 59 women receiving > or = 2 months treatment with an SSRI or venlafaxine for changes in breast size in relation to menopausal status, weight gain and duration of drug therapy. Serum prolactin, estradiol and beta-hCG were also measured before and during treatment in a subgroup of patients. Twenty-three out of 59 patients (39%) reported some degree of mammoplasia. Significantly more SSRI vs. venlafaxine patients reported mammoplasia (p < 0.01). Eighty-four percent with mammoplasia had weight gain vs. 30% without mammoplasia (p < 0.001). The rate of mammoplasia was unrelated to age, menopausal status or duration of treatment. Serum prolactin increased during treatment in the paroxetine subgroup (p < 0.03). In conclusion, antidepressant-induced mammoplasia may be more common than previously expected.

Simultaneous measurement of serotonin and paroxetine in rat brain microdialysate by a single-pump column-switching technique

Simultaneous quantitation of paroxetine and serotonin in rat brain microdialysate is presented as a means to study the neuropharmacokinetics and neuropharmacodynamics of paroxetine, a selective serotonin reuptake inhibitor. In order to achieve this objective, a single-pump column-switching technique was developed. Optimization of the mobile phase in terms of the concentration of ion-pairing agent, pH of mobile phase, temperature of the stationary phase and concentration of organic modifier was investigated and a single mobile phase was developed for both separations. The design was such that the switching valve employed column I (50 mm length) and column II (250 mm length) in series in position A. At 15.3 min, the valve was switched to position B, in which the flow of the mobile phase was directed only through the short column (column I). A flow gradient program was used to increase the flow-rate from 0.125 ml/min to 0.4 ml/min, which enabled a reduction in total analysis time to less than 20 min. The limits of detection for serotonin and paroxetine were 6 fmol and 300 fmol, respectively. The accuracy of the method demonstrated percent differences from spiked samples that were within 12.5% and the precision was found to be within 10% R.S.D.

Headache induced by serotonergic agonists--a key to the interpretation of migraine pathogenesis?

Serotonergic agonists such as m-chlorophenylpiperazine (m-CPP) and fenfluramine may induce migraine attacks. This has led to opposing theories concerning the role of 5-hydroxytryptamine (5HT) in triggering migraine attacks; is there hyperfunction or hypofunction of the central serotonergic system. Our review of the literature strongly suggests that m-CPP and fenfluramine provoke migraine attacks by stimulating, directly or indirectly, the 5HT2C/5HT2B receptors, although there is no total agreement with this interpretation. Central 5HT hypersensitivity in migraine patients, probably due to 5HT neuronal depletion, is proposed on the basis of review of electrophysiological tests and neuroendocrine challenge paradigms.

Tolerance and side-effects of paroxetine in elderly depressed patients

Paroxetine, a selective serotonin reuptake inhibitor (SSRI) antidepressant, is considered to have fewer side-effects than a typical tricyclic antidepressant. As the elderly frequently suffer from adverse effects of psychotropic drugs, safeties and tolerance of paroxetine and their relationship with dose were studied in a double-blind study. Sixteen nondashhospitalised depressed patients, aged 72-86 years, were recruited but 12 patients completed the study. Patients were randomly selected to receive either 15 mg or 30 mg paroxetine daily for 42 days in a double-blind study. A trained nurse made weekly home visits to monitor their medication and general conditions. Patients were assessed at the hospital on days 1, 7, 14, 28 and 42. There were four drop-outs during the first week of study due to lack of motivation, skin rash and upper gastrointestinal symptoms (n=2). Plasma levels of paroxetine showed a dose-related increase in concentrations and indicated a good compliance. At the dosages used, no changes in blood pressure, heart rate, salivary volume, visual choice reaction time, critical flicker fusion threshold and short-term memory were observed in these patients. However, there was a significant improvement in their subjective symptoms (as assessed by a symptom check list and Hamilton Rating Scale) in the 30 mg group, indicating a feeling of well-being.