Drug treatment of depression in frail elderly nursing home residents

The authors conducted a randomized, double-blind, 10-week clinical trial of two doses of nortriptyline in eight nursing homes. Sixty-nine patients, average age 79.5 years, were randomized to receive regular doses (60 mg-80 mg/day) vs. low doses (10 mg-13 mg/day) of nortriptyline. Among the more cognitively intact patients, there was a significant quadratic relationship defining a "therapeutic window" for nortriptyline plasma levels and clinical improvement. There were also significant differences in plasma level-response relationships between depressed patients who were cognitively impaired and those who were more cognitively intact. Depression remains a syndrome that responds to specific treatment, even in frail nursing home patients, and those depressions that occur in patients with significant dementia may represent a treatment-relevant condition with a different plasma level-response relationship than in depression alone.

Clinical pharmacokinetics of mirtazapine

Mirtazapine is the first noradrenergic and specific serotonergic antidepressant ('NaSSA'). It is rapidly and well absorbed from the gastrointestinal tract after single and multiple oral administration, and peak plasma concentrations are reached within 2 hours. Mirtazapine binds to plasma proteins (85%) in a nonspecific and reversible way. The absolute bioavailability is approximately 50%, mainly because of gut wall and hepatic first-pass metabolism. Mirtazapine shows linear pharmacokinetics over a dose range of 15 to 80mg. The presence of food has a minor effect on the rate, but does not affect the extent, of absorption. The pharmacokinetics of mirtazapine are dependent on gender and age: females and the elderly show higher plasma concentrations than males and young adults. The elimination half-life of mirtazapine ranges from 20 to 40 hours, which is in agreement with the time to reach steady state (4 to 6 days). Total body clearance as determined from intravenous administration to young males amounts to 31 L/h. Liver and moderate renal impairment cause an approximately 30% decrease in oral mirtazapine clearance; severe renal impairment causes a 50% decrease in clearance. There were no clinically or statistically significant differences between poor (PM) and extensive (EM) metabolisers of debrisoquine [a cytochrome P450 (CYP) 2D6 substrate] with regard to the pharmacokinetics of the racemate. The pharmacokinetics of mirtazapine appears to be enantioselective, resulting in higher plasma concentrations and longer half-life of the (R)-(-)-enantiomer (18.0 +/-2.5h) compared with that of the (S)-(+)-enantiomer (9.9+/-3. lh). Genetic CYP2D6 polymorphism has different effects on the enantiomers. For the (R)-(-)-enantiomer there are no differences between EM and PM for any of the kinetic parameters; for (S)-(+)-mirtazapine the area under the concentration-time curve (AUC) is 79% larger in PM than in EM, and a corresponding longer half-life was found. Approximately 100% of the orally administered dose is excreted via urine and faeces within 4 days. Biotransformation is mainly mediated by the CYP2D6 and CYP3A4 isoenzymes. Inhibitors of these isoenzymes, such as paroxetine and fluoxetine, cause modestly increased mirtazapine plasma concentrations (17 and 32%, respectively) without leading to clinically relevant consequences. Enzyme induction by carbamazepine causes a considerable decrease (60%) in mirtazapine plasma concentrations. Mirtazapine has little inhibitory effects on CYP isoenzymes and, therefore, the pharmacokinetics of coadministered drugs are hardly affected by mirtazapine. Although no concentration-effect relationship could be established, it was found that with therapeutic dosages of mirtazapine (15 to 45 mg/day), plasma concentrations range on average from 5 to 100 microg/L.

Citalopram in the treatment of depression

OBJECTIVE

To review the efficacy and safety of citalopram in the treatment of depression.

DATA SOURCES

MEDLINE search (1966-April 2000), Current Contents search, additional references listed in articles, and unpublished data obtained from the manufacturer were used to identify data from scientific literature. Studies evaluating citalopram (i.e., abstracts, clinical trials, data on file with the manufacturer) were considered for inclusion.

STUDY SELECTION

English-language literature was reviewed to evaluate the pharmacology, pharmacokinetics, therapeutic use, and adverse effects of citalopram.

DATA EXTRACTION

Controlled animal and human clinical studies published in the English-language literature were reviewed and evaluated. Clinical trials selected for inclusion were limited to those in human subjects and included data from animals if human data were not available.

DATA SYNTHESIS

Citalopram is an antidepressant belonging to the class of selective serotonin-reuptake inhibitors (SSRIs) available for the treatment of depression. Citalopram offers therapeutic efficacy similar to that of the other SSRIs and a more favorable adverse effect profile than that of the tricyclic antidepressants (TCAs). Citalopram does not cause anticholinergic or cardiovascular adverse effects associated with the TCAs. Citalopram is the most selective SSRI and, unlike other SSRIs, seems to be relatively free of interaction mediated by the cytochrome P450 system. Citalopram is also the least expensive antidepressant available to date. This review of citalopram includes data from clinical trials comparing safety, tolerability, efficacy, and pharmacoeconomics with TCAs and SSRIs.

CONCLUSIONS

Clinical trials demonstrate that citalopram's therapeutic efficacy is significantly greater than that of placebo and is comparable with that of other antidepressants. Citalopram has a favorable adverse effect profile, and thus may be useful in treating depressed patients who cannot tolerate anticholinergic or cardiovascular adverse effects associated with TCAs. It may also be useful in patients with comorbid illnesses requiring concomitant medicines.

Pharmacokinetics of mirtazapine and lithium in healthy male subjects

A substantial proportion of patients diagnosed with depression and treated with antidepressants show no or insufficient response. In such patients, lithium is often added to the antidepressant for augmentation. The present study investigated the possible drug-drug interaction between mirtazapine and lithium in 12 healthy male subjects in a randomized, double-blind, placebo-controlled two-period cross-over design. Subjects meeting the inclusion and exclusion criteria were randomly assigned to one of two groups. After an overnight fast, they received either a single oral dose of 600 mg lithium carbonate (16 meq Li+) for 10 days at 08.00 h and a single oral dose of 30 mg mirtazapine at 21.00 h on day 9 or the same number (n = 4) of placebo capsules and and a single oral dose of 30 mg mirtazapine at 21.00 h on day 9. At pre-defined times, blood samples were drawn for the measurement of mirtazapine plasma concentrations and lithium serum concentrations. In addition, psychometric tests were performed and the safety and tolerability of the drugs were assessed. The results indicate that mirtazapine does not alter the pharmacokinetics of lithium and vice versa. In addition, the combination of mirtazapine and lithium appeared to be safe and well-tolerated. Extensive psychometric testing after the administration of mirtazapine did not reveal any differences on any tests in subjects on lithium and placebo, respectively.

Metabolism of desipramine in Japanese psychiatric patients: the impact of CYP2D6 genotype on the hydroxylation of desipramine

We investigated the impact of the genotype of CYP2D6 on the hydroxylation of desipramine in eighteen patients who were administered desipramine hydrochloride per os. Significantly higher plasma concentration of desipramine/daily dose of desipramine/body weight was observed in the subjects with two mutated alleles than in the subjects with either no mutated alleles or one mutated allele (two mutated alleles versus no mutated alleles=530.4+/-215.2 versus 118.1+/-63.9 ng/ml/mg/kg, t=5.68, P<0.001; two mutated alleles versus one mutated allele=530.4+/-215.2 versus 176.2+/-62.3 ng/ml/mg/kg, P<0.001; One-way analysis of variance followed by Bonferroni's multiple comparison test, respectively). Significantly higher ratio of desipramine/2-hydroxy-desipramine was observed in the subjects with two mutated alleles compared to subjects with no mutated alleles or the subjects with one mutated allele (two mutated alleles versus one mutated allele= 4.39+/-0.36 versus 2.00+/-0.64, t=5.12, P<0.001; two mutated alleles versus no mutated alleles=4.39+/-0.36 versus 2.02+/-0.59, t=4.42, P<0.01). The genotyping of CYP2D6 only grossly predicts the steady state concentration of desipramine, mainly predicts the risk of getting very high plasma levels. Within each genotype there is marked interindividual variability.

Blood concentrations of amitriptyline and its metabolite in rats after acute oral administration of amitriptyline

Amitriptyline (AMT), a tricyclic antidepressant that is a dibenzocycloheptadine derivative, is frequently used. However, the case reports of AMT-related fatalities are increased, nowadays, due to the low levels of toxic and fatal concentration in blood. So, this study was carried out to determine the concentrations of AMT and its demethylated metabolite, nortriptyline (NTR), after acute single oral administration of AMT in rats. Blood samples were collected five times from the ophthalmic venous plexus at 0, 1, 2, 4, and 8 h after acute single oral administration of AMT in toxic doses of 10 (Group I) or 20 mg/kg (Group II), and the concentrations of AMT and NTR and the mean ratios of AMT to NTR (AMT/NTR) in the blood were periodically determined at designated times. The blood concentrations of AMT and NTR were identified and quantitated by gas chromatography with thermionic specific detection and gas chromatography-mass spectrometry after solid-phase extraction with a Clean Screen DAU column. The peak blood concentrations of AMT and NTR in Group I were 0.34 and 0.28 microg/mL, respectively, and those of AMT and NTR in Group II were 0.59 and 0.43 microg/mL, respectively, and were reached at 1 h after single oral administration.

The management of postnatal depression

At least one in ten women experiences depression in the weeks or months after the birth of a baby. While many recover spontaneously within a few months, one-third to one-half still have features of depression 6 months after delivery, and some go on to develop a chronic or recurrent mood disorder. Depression in the early postnatal months can have important effects on the mother and her baby, and on other family relationships. Here, we discuss the management of postnatal depression, concentrating on the treatment of women with non-psychotic illness.

Effect of tricyclic antidepressants on taste responses in humans and gerbils

One of the side effects of antidepressant pharmacotherapy reported clinically is impairment of the sense of taste. In this study, the taste effects of four tricyclic antidepressant compounds (clomipramine HCl, desipramine HCl, doxepin HCl, and imipramine HCl) were evaluated experimentally by topical application of the drugs to the tongue. Taste detection threshold concentrations for all four medications ranged from 0.1 mM to 0.2 mM in young persons but were elevated by as much as 7.71 times that in elderly individuals who were taking no concurrent medications. Each compound had a predominantly bitter taste with other qualities including metallic, sour, and sharp-pungent. In addition, each tricyclic antidepressant at concentrations from 1 mM to 5 mM blocked responses to a wide range of taste stimuli in both humans and gerbils. The differential suppression of other tastes by tricyclic antidepressants at the level of the taste receptors may contribute to the clinical reports of dysgeusia and hypogeusia.

Penetration of amitriptyline, but not of fluoxetine, into brain is enhanced in mice with blood-brain barrier deficiency due to mdr1a P-glycoprotein gene disruption

Mice with a genetic disruption (knockout) of the multiple drug resistance (Mdr1a) gene were used to examine the effect of the absence of the drug-transporting P-glycoprotein at the blood-brain barrier on the uptake of amitriptyline (AMI) and fluoxetine (FLU) and their metabolites into the brain. One hour after intraperitoneal injection of AMI or FLU, knockout (-/-) and wild-type (+/+) mice were sacrificed and drug concentrations of brain, kidney, liver, testis, and plasma were measured. The plasma concentrations of the AMI metabolites and the brain:spleen ratios of AMI, nortriptyline (NOR), 10-OH-AMI and 10-OH-NOR were significantly higher in the -/- mice, demonstrating that AMI and its metabolites are substrates of the P-glycoprotein and that mdr1a activity at the level of the blood-brain barrier reduces the penetration of these substances into the brain. In contrast, tissue distributions of FLU and its metabolites among the various tissues tested were indistinguishable between groups. The herein reported differences in brain penetration of antidepressant drugs depending on the presence of the mdr1a gene may offer an explanation for differences in the treatment response at a given plasma concentration. Moreover, individual differences in mdr1 gene activity may account for variable response patterns at different episodes and development of therapy resistance.

Effect of clomipramine on monoamine metabolites in the cerebrospinal fluid of behaviorally normal dogs

The tricyclic antidepressant, clomipramine, is an effective treatment for canine compulsive disorder (canine CD). This disorder is a clinical syndrome of abnormal conflict behaviors and its pathophysiology is unknown. However, because clomipramine is an effective treatment, information about the drug's neurochemical effect could enhance the understanding of canine CD. The following experiment used 6 behaviorally normal dogs to assess the effect of clomipramine (3 mg/kg, q24h, PO) on the central turnover of 3 monoamines (serotonin, dopamine, and norepinephrine) as measured by the concentrations of their respective metabolites in cerebrospinal fluid (CSF). In a randomized, placebo-controlled, AB-BA crossover experiment, cisternal CSF was taken after 1, 2, 4, and 6 wk on each treatment. No effect of clomipramine was detected. This contrasts with human studies that have suggested that clomipramine affects the concentrations of monoamine metabolites in lumbar CSF. However, those papers do not address methodological assumptions, such as (i) metabolites in CSF originate only from the brain, and (ii) concentrations of metabolites in cisternal/lumbar CSF reflect the concentrations in local areas of the brain. Notwithstanding the small sample size, our results suggest that more localized sampling techniques (e.g. microdialysis) are needed when examining the effect of drugs on central monoamine metabolites. Clomipramine's efficacy for canine CD indicates the need for neurobiological research and, to our knowledge, our study is the first of its kind in dogs. The resulting data are preliminary but they can inform optimal neurobiological studies of canine CD.

Pharmacokinetics of clomipramine in dogs following single-dose intravenous and oral administration

OBJECTIVE

To determine pharmacokinetics of clomipramine and its principle metabolite (desmethylclomipramine) in the plasma of dogs after IV or oral administration of a single dose.

ANIMALS

6 male and 6 female Beagles.

PROCEDURES

Clomipramine was administered IV (2 mg/kg), PO (4 mg/kg) after food was withheld for 15 hours, and PO (4 mg/kg) within 25 minutes after dogs were fed. Plasma clomipramine and desmethylclomipramine concentrations were measured by use of a gas chromatography with mass-selection method.

RESULTS

Time to peak plasma concentrations of clomipramine and desmethylclomipramine following oral administration was 1.2 hours. For clomipramine, after IV administration, elimination half-life was 5 hours, mean residence time was 3 hours, and plasma clearance was 1.4 L/h/kg. Values for mean residence time and terminal half-life following oral administration were similar to values obtained following IV administration, and systemic bioavailability was approximately 20% for clomipramine and 140% for desmethylclomipramine, indicating fast absorption of clomipramine from the gastrointestinal tract and extensive first-pass metabolism. Administration of clomipramine with food did not alter the area under the concentration versus time curve for desmethylclomipramine but resulted in a 25% increase for clomipramine. Clomipramine and desmethylclomipramine were extensively bound (> 96%) to serum proteins. There were no significant differences in area under the concentration versus time curve between male and female dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate that there should not be any clinically important differences in efficacy regardless of whether clomipramine is administered with or without food.

Pharmacokinetics of clomipramine in dogs following single-dose and repeated-dose oral administration

OBJECTIVE

To determine pharmacokinetics of clomipramine and its principle metabolite (desmethylclomipramine) in the plasma of dogs following single-dose and repeated-dose oral administration at various dosages.

ANIMALS

9 male and 9 female Beagles.

PROCEDURES

Clomipramine was administered orally at a dose of 1, 2, or 4 mg/kg to 3 male and 3 female dogs, first as a single dose and then, after an interval of 14 days, twice daily for 10 days. Plasma clomipramine and desmethylclomipramine concentrations were measured by use of a gas chromatography with mass-selection method.

RESULTS

Dose-related accumulation was detected following repeated-dose administration. Accumulation ratios after administration of clomipramine at dosages of 1, 2, and 4 mg/kg twice daily were 1.4, 1.6, and 3.8, respectively, for clomipramine and 2.1, 3.7, and 7.6, respectively, for desmethylclomipramine. Terminal half-life increased slightly (1.6-fold for clomipramine and 1.2-fold for desmethylclomipramine) with repeated-dose administration but remained short in all groups (< or = 4 hours). Steady state was reached within 4 days in all animals. Ratios of the areas under the concentration versus time curves from time 0 to 12 hours for clomipramine and desmethylclomipramine were 3.9, 3.1, and 1.5 after repeated administration at dosages of 1, 2, and 4 mg/kg every 12 hours, respectively. Areas under the concentration versus time curve, mean residence times, and terminal half-lives were not significantly different between male and female dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Repeated administration of clomipramine results in higher concentrations of clomipramine than desmethylclomipramine in dogs.

Interactions between anticonvulsant and psychoactive drugs

This review considers the relevance of pharmacokinetic interactions between antiepileptic drugs (AEDs) and psychoactive drugs in the treatment of mood disorders in patients with epilepsy. The determination of plasma levels of some of these drugs (mainly the AEDs) has enabled clinicians to evaluate the kinetic modifications during the course of such combined therapies and to adjusting the dosages in cases of subtherapeutic or toxic levels. In general, phenobarbital, phenytoin, and carbamazepine stimulate the catabolic degradation of tricyclic antidepressants (TCAs), and TCAs have an inhibitory effect on the elimination of AEDs. The newer antidepressants that selectively inhibit the reuptake of serotonin (SSRIs), although in different fashions for the different substances (fluoxetine, fluvoxamine, paroxetine) may cause an increase of plasma AED levels through inhibition of the isoenzyme P450 2D6. Similarly, antipsychotics (APs) are more rapidly metabolized when AEDs are co-administered, whereas AED metabolism is scarcely influenced by AP. Finally, plasma levels of tranquilizers are lowered by AED co-therapy. As the concomitant administration of AED and psychoactive drugs becomes increasingly used for treatment of mood disorders in patients with or without epilepsy, therapeutic drug monitoring may be useful in designing correct and rational therapy.

Increased bioavailability of clomipramine after sublingual administration in rats

This study examined the absorption and disposition of clomipramine in rats after sublingual (5 and 50 mg/kg), oral (50 mg/kg), and iv (5 mg/kg) administration. The mean oral bioavailability of clomipramine was 24.8% and 29.7%, respectively, in conscious rats and in rats anesthetized with ketamine/xylazine (30/3 mg/kg). When given sublingually in isotonic saline at a dose of 50 mg/kg, clomipramine was rapidly absorbed, and the mean absolute bioavailability (36.2%) was increased over oral dosing. The mean AUC values of clomipramine were 2258 +/- 1762 ng.h/mL and 1891 +/- 867 ng.h/mL after oral administration to conscious and anesthetized rats, respectively, and 3303 +/- 1576 ng.h/mL after sublingual administration to anesthetized rats. Sublingual administration (5 mg/kg doses) of clomipramine formulated with a permeation enhancer, 2-hydroxypropyl beta-cyclodextrin, further increased the sublingual bioavailability to 57.1%. The sublingual route may be an alternative route of administration of clomipramine, providing enhanced bioavailability.

Citalopram: an interaction study with clomipramine in a patient heterozygous for CYP2D6 genotype

A pharmacokinetic interaction between the selective serotonin reuptake inhibitor citalopram and a tricyclic antidepressant, clomipramine, was noted in a patient treated for major depression and obsessive-compulsive disorder. After the addition of citalopram, a desmethylclomipramine plasma level increase and an 8-hydroacy-desmethylclomipramine plasma level decrease were observed. The CYP2D6 phenotype, determined when the patient received the antidepressant comedication, characterized a poor metabolizer status (dextromethorphan metabolic ratio >0.3), despite a heterozygous genotype containing a wild-type allele with extensive metabolic capacity and a mutant non-functional allele (CYP2D6*1A/CYP2D6*4A). This case seems to be one of the first descriptions of the clinical relevance of a CYP2D6 heterozygous genotype in a patient treated with antidepressant.

Distribution of mirtazapine (Remeron) in thirteen postmortem cases

Mirtazapine is a new antidepressant agent that entered the United States market in April 1996. To date, the literature provides limited information about therapeutic blood concentrations and virtually no information about postmortem levels. The Los Angeles County Coroner's Toxicology Laboratory has encountered 13 cases where postmortem tissue distributions of mirtazapine were determined. The analysis of mirtazapine from postmortem specimens (2-mL sample size) consisted of an n-butylchloride basic extraction procedure with identification and quantitation on a gas chromatograph-nitrogen-phosphorus detector. Linearity was achieved from 0.025 mg/L to 3.0 mg/L with a limit of quantitation of 0.025 mg/L. Confirmation of mirtazapine was performed on a gas chromatograph-mass spectrometer by comparison with a pure analytical standard. The tissue distribution of mirtazapine are in the following concentration ranges: heart blood 0.03-0.57 mg/L (13 cases), femoral blood 0.04-0.24 mg/L (9 cases), vitreous 0.06-0.10 mg/L (3 cases), liver 0.32-2.1 mg/kg (12 cases), bile 0.40-6.6 mg/L (7 cases), urine 0.12-2.5 mg/L (11 cases), kidney 0.23 mg/kg (1 case), spleen 0.17 mg/kg (1 case), and gastric 0.001-2.7 mg total (9 cases). Mirtazapine was not implicated in the cause of death in any of the 13 cases studied. These cases are being presented to aid the forensic toxicologist in the evaluation of postmortem mirtazapine levels.

Tissue distribution of mirtazapine (Remeron) in postmortem cases

Mirtazapine (Remeron) is a member of the relatively new class of tetracyclic antidepressants. There are published cases of mirtazapine's detection as an incidental finding in postmortem cases; however, case reports with associated tissue concentrations and interpretations are not available. This report documents the tissue distribution of mirtazapine in eight postmortem cases in which it was identified but did not contribute to the cause or manner of death. The following mean mirtazapine concentrations (milligrams per liter or milligrams per kilogram) were found: heart blood 0.12 (range, < 0.01-0.33, n = 7); peripheral blood 0.09 (< 0.01-0.14, n = 4); urine 0.61 (0.01-3.2, n = 7); liver 0.88 (0.04-3.6, n = 6), kidney 0.21 (0.02-0.48, n = 5); and bile 0.62 (0.11-1.6, n = 6). In each case, the mirtazapine concentration in heart blood was approximately equal to that of peripheral blood, indicating that postmortem redistribution was not a factor in evaluating postmortem blood concentrations in these cases. However, because the liver mirtazapine concentrations were 5-30 times the blood concentrations, the potential for postmortem redistribution cannot be excluded. Additionally, because urine concentrations of the parent compound were consistently greater than the blood concentrations, urine is an adequate screening specimen for mirtazapine.

Biotransformation of doxepin by Cunninghamella elegans

A filamentous fungus, Cunninghamella elegans ATCC 9245, was used as a microbial model of mammalian metabolism to biotransform doxepin, a tricyclic antidepressant drug. Doxepin is produced as an 85:15% mixture of the trans- (E) and cis- (Z) forms. After 96 h of incubation in Sabouraud dextrose broth, 28% of the drug was metabolized to 16 metabolites. No change in the trans- (E) and cis- (Z) ratio of doxepin was observed. Metabolites were isolated by reversed phase HPLC and identified by (1)H NMR and mass spectroscopic analysis. The major metabolites were (E)-2-hydroxydoxepin, (E)-3-hydroxydoxepin, (Z)-8-hydroxydoxepin, (E)-2-hydroxy-N-desmethyldoxepin, (E)-3-hydroxy-N-desmethyldoxepin, (E)-4-hydroxy-N-desmethyldoxepin, (Z)- and (E)-8-hydroxy-N-desmethyldoxepin, (E)-N-acetyl-N-desmethyldoxepin, (E)-N-desmethyl-N-formyldoxepin, (E)-N-acetyldidesmethyldoxepin, (E)-and (Z)-doxepin-N-oxide, and (E)- and (Z)-N-desmethyldoxepin. Six of the metabolites produced by C. elegans were essentially similar to those obtained in human metabolism studies, although nine novel metabolites were identified.

Pronounced differences in the dispositon of clomipramine between Japanese and Swedish patients

The aim of this study was to compare the disposition of the tricyclic antidepressant clomipramine (C) in Japanese and Swedish patients receiving continuous treatment. Therapeutic drug monitoring data for C and the active metabolite N-desmethylclomipramine (DC) in Japanese patients receiving monotherapy (N = 12) and in those receiving C plus benzodiazepines (BZDs) (N = 96) as well as in Swedes receiving C monotherapy (N = 131) and in those receiving C plus BZDs (N = 43) were used. A population kinetic approach with Bayesian feedback was used to estimate the individual clearance values for C. The relationships between kinetic variables and covariates were evaluated by linear multiple regression. The median (25% and 75% quartiles, respectively) oral clearance of C was 12.7 L/hr (11.6, 30.6) in Japanese patients receiving C monotherapy, 18.1 L/hr (5.6, 31.8) in Japanese patients receiving C plus BZDs, 62.7 L/hr (40.0, 90.6) in Swedish patients receiving C monotherapy, and 56.5 L/hr (34.3, 74.1) in Swedish patients receiving C plus BZDs. When combining all populations in a linear multiple regression, clearance was correlated with ethnic group (p < 0.00001) and age (p < 0.0005), but it was uncorrelated with gender, body weight, and administration of BZDs. The C/DC plasma concentration ratios were 1.08 in Japanese patients receiving C monotherapy, 0.90 in Japanese patients receiving C plus BZDs, 0.51 in Swedish patients receiving C monotherapy, and 0.49 in Swedish patients receiving C plus BZDs. Thus, the lower oral clearance of C in Japanese patients compared with that in Swedish patients is not accounted for by the lower body weight in Japanese patients or by concomitant treatment with BZDs and is therefore likely to be a true ethnic difference. The higher C/DC ratio implicates a more pronounced serotonergic than noradrenergic effect in Japanese patients than in Swedish patients.

Development of predictive retention-activity relationship models of tricyclic antidepressants by micellar liquid chromatography

The distribution of tricyclic antidepressants from plasma to brain, where these drugs exert their main clinical action, and other organs is related to transport events across the cell membranes of the different tissues. It could be expected that all the molecular features that condition the transport processes (mainly hydrophobicity and molar total charge) also control the pharmacokinetic and biochemical behavior. Micellar liquid chromatography (MLC) has been proposed to emulate in vitro the partitioning process in the biomembranes. The use of micellar solutions of Brij35 as mobile phases in reversed-phase liquid chromatography has proven to be valid to predict the biological activities of local anesthetics, barbiturates, catecholamines, and benzodiazepines. In this paper, the relationships between the capacity factor in MLC and some pharmacokinetic parameters and biological responses of tricyclic antidepressants are studied. Predictive regression models for the estimation of these parameter values, using the logarithm of the retention data (log k) as independent variable, are also proposed.

Comparison of the effects of antidepressants and their metabolites on reuptake of biogenic amines and on receptor binding

1. The present survey compares the effects of antidepressants and their principal metabolites on reuptake of biogenic amines and on receptor binding. The following antide-pressants were included in the study: the tricyclic antidepressants amitriptyline, dothiepin, and lofepramine and the atypical antidepressant bupropion, which all have considerable market shares in the UK and/or US markets; the selective serotonin reuptake inhibitors (SSRIs) citalopram, fluoxetine, fluvoxamine, paroxetine, and sertraline; and the recently approved antidepressants venlafaxine and nefazodone. 2. Amitriptyline has similar in vitro reuptake inhibitory potencies for 5-HT and NA, whereas the metabolite nortriptyline is preferentially a NA reuptake inhibitor. Both amitriptyline and nortriptyline are also 5-HT2 receptor antagonists. 3. Dothiepin has equipotent 5-HT and NA reuptake inhibitory activity, whereas northiaden shows a slight selectivity for NA reuptake inhibition. Dothiepin and northiaden are also 5-HT2 receptor antagonists. The slow elimination rate of northiaden (36-46 hr) compared to dothiepin (14-24 hr) suggests that northiaden contributes significantly to the therapeutic effect of dothiepin. 4. Lofepramine is extensively metabolized to desipramine. Desipramine plays an important role in the antidepressant activity of lofepramine, as the plasma elimination half-life of lofepramine (4-6 hr) is much shorter than that of desipramine (24 hr). Both compounds are potent and selective inhibitors of NA reuptake. 5. The five approved SSRIs, citalopram, fluoxetine, fluvoxamine, paroxetine, and sertraline, are potent 5-HT reuptake inhibitors, and the demethyl metabolites, norfluoxetine, demethylsertraline, and demethylcitalopram, also show selectivity. Paroxetine and sertraline are the most potent inhibitors of 5-HT reuptake, whereas citalopram is the most selective. Fluoxetine is the least selective and the metabolite of fluoxetine, norfluoxetine, is a more selective and more potent 5-HT reuptake inhibitor than the parent compound and has an extremely long half-life (7-15 compared to 1-3 days). Thus the metabolite plays an important role for the therapeutic effect of fluoxetine. Fluoxetine is also a 5-HT2C receptor antagonist. Demethylsertraline is a weaker and less selective 5-HT reuptake inhibitor in vitro than sertraline, but demethylsertraline has a very long half-life (62-104 hr) compared to the parent compound (24 hr) and it might play a role in the therapeutic effects of sertraline. Demethylcitalopram has about a 10 times lower 5-HT reuptake inhibitory potency in vitro than citalopram, and the elimination half-lives are approximately 1.5 and 2 days, respectively. 6. Bupropion and hydroxybupropion are weak inhibitors of biogenic amine reuptake. The mechanisms of action responsible for the clinical effects of bupropion are not fully understood, but it has been suggested that both dopaminergic and noradrenergic components play a role and that the hydroxybupropion metabolite contributes significantly to the antidepressant activity. 7. Venlafaxine and O-demethylvenlafaxine are weak inhibitors of 5-HT and NA reuptake, and the selectivity ratios are close to one. O-Demethylvenlafaxine is eliminated more slowly than venlafaxine (plasma half-lives of 5 and 11 hr, respectively), and it is likely that it contributes to the overall therapeutic effect of venlafaxin. 8. Nefazodone and alpha-hydroxynefazodone are equipotent 5-HT and NA reuptake inhibitors. Both compounds are also 5-HT2 receptor antagonists. Both parent compound and metabolite have short elimination half-lives.

Amitriptyline absorption in a patient with short bowel syndrome

Oral drug therapy in patients with short bowel syndrome can be quite challenging. We report the case of a 40-yr-old woman with short bowel syndrome and depression requiring antidepressant drug therapy. After buccal administration of amitriptyline, therapeutic serum antidepressant concentrations were attained despite the patient having only 18 inches of proximal small bowel. Clinical improvement in mood was seen, with the only drug side effects being dry mouth and bitter drug taste. Buccal absorption likely is playing a major role in attaining therapeutic serum tricyclic antidepressants drug concentrations.