A fatal case of desvenlafaxine and paroxetine poisoning

Desvenlafaxine (O-desmethylvenlafaxine) and paroxetine are antidepressants that inhibit serotonin reuptake. Despite their relatively safe profiles, several serious side effects, including serotonin syndrome, bleeding, mania, and high blood pressure, are observed. We report the confirmation of the death of a 41-year-old female, with an overdose of desvenlafaxine and paroxetine suspected as the main cause of death. To quantify the level of desvenlafaxine and paroxetine in whole blood and urine, solid phase extraction combined with liquid chromatography-tandem mass spectrometry was developed and validated. Calibration curves were linear with coefficients of determination (r2) >0.999 for desvenlafaxine and paroxetine. The limits of detection and the limits of quantification for both desvenlafaxine and paroxetine were 0.001 µg/mL and 0.02 µg/mL, respectively. Desvenlafaxine and paroxetine were detected in the postmortem samples, along with various psychiatric drugs, and the blood alcohol content level was below 0.010%. The concentrations of desvenlafaxine and paroxetine in the heart blood were 11.0 µg/mL and 2.1 µg/mL, respectively, indicating lethal concentrations. In the urine, the concentrations of desvenlafaxine and paroxetine were 87.7 µg/mL and 3.5 µg/mL, respectively. This is the first report to determine the blood concentration of desvenlafaxine in a fatal intoxication caused by an overdose of desvenlafaxine single formulation.

Selective serotonin reuptake inhibitors and venlafaxine in pregnancy: Changes in drug disposition

Background

Pregnancy may cause changes in drug disposition. The clinical consequences may be profound and even counterintuitive; in some cases pregnant women may need more than twice their usual drug dose in order to maintain therapeutic drug levels. For antidepressants, evidence on drug disposition in pregnancy is scarce. The aim of this study was to determine the effects of pregnancy on serum levels of selective serotonin reuptake inhibitors (SSRIs) and venlafaxine in a large and naturalistic patient material, in order to provide tentative dose recommendations for pregnant women.

Methods

Using patient data from two routine therapeutic drug monitoring (TDM) services in Norway with linkage to the national birth registry, dose-adjusted serum drug concentrations of SSRIs and venlafaxine during pregnancy were compared to the women’s own baseline (non-pregnant) values, using a linear mixed model.

Findings

Overall, the TDM databases contained 196,726 serum concentration measurements from 54,393 women. After data linkage and drug selection (SSRIs or venlafaxine only), we identified 367 analyses obtained from a total of 290 pregnancies in 281 women, and 420 baseline observations from the same women. Serum concentrations in the third trimester were significantly lower than baseline for paroxetine (–51%; 95% confidence interval [CI], –66%, –30%; p<0.001), fluvoxamine (–56%; CI, –75%, –23%; p = 0.004) and citalopram (–24%; CI, –38%, –7%; p = 0,007), and higher than baseline for sertraline (+68%; CI, +37%, +106%; p<0.001). For escitalopram, fluoxetine and venlafaxine concentrations did not change significantly.

Conclusions

For paroxetine and fluvoxamine the pronounced decline in maternal drug serum concentrations in pregnancy may necessitate a dose increase of about 100% during the third trimester in order to maintain stable concentrations. For fluoxetine, venlafaxine, citalopram, escitalopram and sertraline, the present study indicates that dose adjustments are generally not necessary during pregnancy.

Paroxetine-induced increase in activity of locus coeruleus neurons in adolescent rats: implication of a countertherapeutic effect of an antidepressant

The concern that antidepressant (AD) drugs, especially selective serotonin reuptake inhibitors and paroxetine (PAR) in particular, can increase suicidality during the early treatment of juvenile patients (children and adolescents) has created a dilemma for clinicians treating depressives. Although preclinical research cannot resolve controversy in this area, our present findings may provide insight into how AD drugs might, under certain conditions, exacerbate rather than ameliorate the depressive state. Both clinical and preclinical evidences indicate that the principal noradrenergic cell group in the brain, the locus coeruleus (LC), is overactive in depressives and that, conversely, effective AD treatments decrease the activity of LC neurons. We report here that short-term (2 and 4 days) administration of PAR produces an increase in the activity of LC neurons (spontaneous firing rate and sensory-evoked responses) in young rats, contrary to the 'therapeutic' decrease in activity typically observed in adult rats. Blood levels of PAR were lower in young rats than in adult rats, although similar low blood levels produced by a lower dose of PAR in adult rats failed to produce an increase in LC activity. In addition, activity of young rats in the swim test was determined to assess depressive-like responses. The same dose/durations of PAR, which produced the largest increases in LC activity in young rats, produced decreases in swim-test activity, indicating that brief administration of PAR in young rats can promote, rather than reduce, the depressive state. These results offer a model that may help screen potential adjunctive treatments to avoid early adverse effects of ADs.

Quantification of paroxetine in human plasma by liquid chromatography coupled with electrospray ionization tandem mass spectrometry

A rapid LC coupled with electrospray ionization (ESI) MS/MS method was developed and validated for the quantification of paroxetine in heparinized human plasma. The plasma samples were prepared by the solid-phase extraction method without drying or reconstitution. Elution was done with 0.5 mL 0.2% (v/v) formic acid in methanol-acetonitrile (65 + 35, v/v). The analyte and the internal standard (IS; imipramine hydrochloride) were chromatographed on a BDS Hypersil C18 column. The analyte was analyzed by LC/MS/MS with only 1.7 min run time. An ESI interface was chosen for ionization of the analyte from the sample matrix. Selected reaction monitoring mode for detection of paroxetine and the IS were achieved by using m/z 330.17/192.10 and 281.13/86.14, respectively. The LC retention times for paroxetine and imipramine were 0.94 and 1.05 min, respectively. The method was linear in the concentration range of 0.5-80.0 ng/mL with r > or = 0.9995. Recovery of paroxetine and imipramine ranged from 90 to 95%. The assay has been successfully applied to bioequivalence study samples for estimation of paroxetine in healthy human subjects.

New nonextractive and highly sensitive high-performance liquid chromatographic method for determination of paroxetine in plasma after offline precolumn derivatization with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole

New nonextractive and simple offline precolumn derivatization procedures have been proposed, for the first time, for the trace determination of paroxetine (PXT) in human plasma by HPLC with fluorescence detection. Trimetazidine (TMZ) was used as an internal standard. Plasma samples were treated with acetonitrile for protein precipitation and then derivatized with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole in borate buffer of pH 8 at 70 degrees C for 30 min. Separations of the derivatized PXT and TMZ were performed on a Nucleosil CN column using a mobile phase consisting of acetonitrile-10 mM sodium acetate buffer (pH 3.5)-methanol (47 + 47 + 6, v/v) at a flow rate of 1.0 mL/min. The derivatized samples were excited at 470 nm and monitored at an emission wavelength of 530 nm. Under the optimum chromatographic conditions, a linear relationship with good correlation coefficient (r = 0.9998, n = 7) was found between the peak area ratio and PXT concentrations in the range of 5-600 ng/mL. The LOD and LOQ were 1.37 and 4.14 ng/mL, respectively. The intraday and interassay precisions were satisfactory; the RSD did not exceed 4.2%. The accuracy of the method was proved by recovery of PXT from spiked human plasma at levels of 97.28-104.38 +/- 0.41-3.62%. The proposed method had high throughput, as the analysis involved a simple sample pretreatment procedure and short run time (< 10 min). The results demonstrated that the method would have a great value when it is applied in the therapeutic monitoring of PXT.

Serotonin transporter genotype interacts with paroxetine plasma levels to influence depression treatment response in geriatric patients

OBJECTIVE

To investigate whether variable antidepressant response may be influenced by an interaction between the serotonin transporter promoter polymorphism (5-HTTLPR) and antidepressant concentration.

METHODS

Elderly subjects with depression treated with paroxetine (n = 110) were genotyped and assessed with the Hamilton Rating Scale for Depression (HAMD). A mixed-effect analysis of repeated measures was used.

RESULTS

There was an interaction between early paroxetine concentration and 5-HTTLPR genotype on symptomatic improvement over 12 weeks (F(18,59.5) = 1.8, p < 0.05), as well as main effects of both paroxetine concentration (F(68,55.3) = 2.4, p < 0.005) and genotype (F(2,74.2) = 5.7, p < 0.005). Paroxetine concentrations were correlated with change in HAMD scores after 2 weeks of treatment in subjects with the short (s) allele (r = 0.31, p < 0.05) but not in subjects homozygous for the long (l) allele.

CONCLUSION

The results demonstrate a concentration-response relation for paroxetine in late-life depression and support the hypothesis for both a direct main effect and a moderating influence of 5-HTTLPR alleles on this concentration-response relation.

Genetic polymorphisms in the 5-hydroxytryptamine type 3B receptor gene and paroxetine-induced nausea

Selective serotonin reuptake inhibitor (SSRI)-induced nausea can be severe enough to lead to early treatment discontinuation. However, it is currently not possible to predict the occurrence of nausea before the initiation of SSRI treatment. In this study, we investigated the effect of genetic polymorphisms in the 5-hydroxytryptamine type 2A, 3A, and 3B (5-HT3B) receptors, 5-HT transporter, and CYP2D6 genes on the incidence of paroxetine-induced nausea. A consecutive series of 72 Japanese patients with depressive or anxiety disorders were treated with paroxetine. Paroxetine-induced nausea was assessed by a pharmacist and was observed in 29.2% of the patients. A significant (nominal p=0.00286) association was found between the incidence of nausea and the -100_-102AAG insertion/deletion polymorphism of the 5-HT3B receptor gene. No significant associations were observed between the other genetic polymorphisms and the incidence of nausea. The -100_-102AAG deletion variant of the 5-HT3B receptor gene may affect paroxetine-induced nausea.

Determination of paroxetine in plasma by liquid chromatography coupled to tandem mass spectrometry for pharmacokinetic and bioequivalence studies

A rapid and validated liquid chromatography coupled to tandem mass spectrometric method (LC-MS-MS) has been developed and applied to pharmacokinetic and bioequivalence studies in 24 healthy male Korean volunteers. The procedure involves a liquid-liquid extraction of paroxetine (CAS 61869-08-7) and fluoxetine (internal standard, CAS 54910-89-3) with ether/methyl chloride (7:3, v/v) and separated by LC equipped with C18 column using acetonitrile: 5 mmol/L ammonium formate (4:3, v/v) as mobile phase. Detection is carried out on an API 2000 MS system by multiple reactions monitoring mode. The ionization was optimized using ESI(+) and selectivity was achieved by MS-MS analysis, mlz 330.0-->192.0 and m/ z 310-->148 for paroxetine and fluoxetine, respectively. The method has a total run time of 1.5 min and was linear over a working range of 0.05-20 ng/mL and the lower limit of quantification was 0.05 ng/ mL. No endogenous compounds were found to interfere with the analysis. The inter-day and intra-day accuracy was in the ranges of 102.69-107.79% and 102.07-109.57%, respectively and precision of inter-day and intra-day expressed as relative standard deviation were 1.86-9.99% and 1.52-6.28%, respectively. The validation of this method on linearity, specificity, accuracy, precision as well as applicability to pharmacokinetic and bioequivalence studies by analysis of blood samples taken up to 72 h after oral administration of 20 mg of paroxetine in 24 healthy volunteers were found to be good performance.

Effect of itraconazole on pharmacokinetics of paroxetine: the role of gut transporters

A recent in vitro study has shown that paroxetine is a substrate of P-glycoprotein. However, there was no in vivo information indicating the involvement of P-glycoprotein on the pharmacokinetics of paroxetine. The aim of this study was to examine the effects of itraconazole, a P-glycoprotein inhibitor, on the pharmacokinetics of paroxetine. Two 6 day courses of either 200 mg itraconazole daily or placebo with at least a 4 week washout period were conducted. Thirteen volunteers took a single oral 20 mg dose of paroxetine on day 6 of both courses. Plasma concentrations of paroxetine were monitored up to 48 hours after the dosing. Compared with placebo, itraconazole treatment significantly increased the peak plasma concentration (Cmax) of paroxetine by 1.3 fold (6.7 +/- 2.5 versus 9.0 +/- 3.3 ng/mL, P < 0.05) and the area under the plasma concentration-time curve from zero to 48 hours [AUC (0-48)] of paroxetine by 1.5 fold (137 +/- 73 versus 199 +/- 91 ng*h/mL, P < 0.01). Although elimination half-life differed significantly (16.1 +/- 3.4 versus 18.8 +/- 5.9 hours, P < 0.05), the alteration was small (1.1 fold). The present study demonstrated that the bioavailability of paroxetine was increased by itraconazole, suggesting a possible involvement of P-glycoprotein in the pharmacokinetics of paroxetine.

Simultaneous Determination of Nontricyclic Antidepressants in Human Plasma by Solid-Phase Microextraction and Liquid Chromatography (SPME-LC)

A sensitive, selective, and reproducible solid-phase microextraction and liquid chromatographic (SPME-LC) method for simultaneous determination of mirtazapine, citalopram, paroxetine, fluoxetine, and sertraline in human plasma was developed, validated, and further applied to analyze plasma samples obtained from patients with depression. Important factors in the optimization of SPME efficiency are discussed, including the fiber coating, extraction time, pH, ionic strength, influence of plasma proteins, and desorption conditions. The limit of quantitation of the nontricyclic antidepressants in plasma varied from 25 to 50 ng/mL with a coefficient of variation lower than 5%. The response of the SPME-LC method for most of the drugs was linear over a dynamic range of 50 to 500 ng/mL, with all of them having correlation coefficients greater than 0.9970. The performance of the SPME-LC method allowed the nontricyclic antidepressants analyses in therapeutic levels.

Time course of response to paroxetine: influence of plasma level

Early improvement of depression severity is considered an important therapeutic goal, predictive of later remission. The present study aimed at testing the hypothesis that plasma concentration might influence the time course of response to paroxetine. Eighty-four patients with a severe depressive episode started paroxetine 20 mg/day, with a possible dose adjustment to 30 mg/day after 2 weeks. Severity of depression (Montgomery-Asberg Depression Rating Scale) was assessed at weeks 0, 2 and 4 for all patients, and every 2 weeks thereafter until discontinuation. Median duration on paroxetine was 6 weeks (range 4-18 weeks). Plasma concentration was measured at steady-state after 2 weeks at 20 mg/day. In a first stage, pattern analysis led to distinguish patients with non-response, non-persistent response, early persistent response (obtained at week 2) and delayed persistent response (week 4 or later). Comparison of patients with (n=29, 34.5%) and without persistent response (n=55, 65.5%) did not reveal any significant difference, whereas focus on patients with persistent response indicated that shorter time to response was significantly associated with shorter duration of current episode (r(S)=0.54, p=0.003) and higher plasma level (r(S)=-0.47, p=0.011). In a second stage, a sigmoid mixed effects model was developed that adequately fitted depression severity versus time profiles among patients with persistent response (n=157 data for 29 patients). Estimated median time to response was 3.2 weeks (range 0.9-6.6). Higher paroxetine concentration, younger age and shorter episode duration were confirmed as significant determinants of a shorter time to response (likelihood ratio tests, p<0.005). The present study supports the hypothesis that higher paroxetine concentration might contribute to hasten relief of depressive symptoms in severely depressed patients.

Determination of the antidepressant paroxetine and its three main metabolites in human plasma by liquid chromatography with fluorescence detection

A high-performance liquid chromatographic method has been developed for the determination in human plasma of the specific serotonin reuptake inhibitor (SSRI) antidepressant paroxetine and its three main metabolites (M1, M2, M3). Fluorescence detection was used, exciting at lambda = 294 nm and monitoring emission at lambda = 330 nm for paroxetine (lambda(exc) = 280 nm, lambda(em) = 330 nm for M1 and M2; lambda(exc) = 268 nm, lambda(em) = 290 nm for M3). Separation was obtained on a reversed-phase C18 column using a mobile phase composed of 66.7% aqueous phosphate at pH 2.5 and 33.3% acetonitrile. Imipramine (lambda(exc) = 252 nm, lambda(em) = 390 nm) was used as the internal standard. A careful pre-treatment of plasma samples was developed, using solid-phase extraction with C8 cartridges (50 mg, 1 mL). The calibration curves were linear over a working range of 2.5-100 ng mL(-1) for paroxetine and of 5-100 ng mL(-1) for all metabolites. The limit of detection (LOD) was 1.2 ng mL(-1) for PRX and 2.0 ng mL(-1) for the metabolites. The method was applied with success to plasma samples from depressed patients undergoing treatment with paroxetine. Hence, the method seems to be suitable for the therapeutic drug monitoring of paroxetine and its main metabolites in depressed patients' plasma.

Altered HDAC5 and CREB mRNA expressions in the peripheral leukocytes of major depression

BACKGROUND

Gene expressions of the peripheral leukocytes in depressive patients might reflect the systemic dysfunction of major depression. We determined mRNA expression levels of Histone deacetylase 5 (HDAC5) gene and cyclic AMP response element-binding protein 1 (CREB) gene in the leukocyte of depressive patients. HDAC5 and CREB are reported to be important targets of antidepressants, the latter being located in the downstream of the former in lymphocyte calcium signaling.

METHODS

25 patients with major depression and 25 age- and sex-matched healthy controls were included in this study. Twenty patients were able to be followed up until the 8 week-treatment. The mRNA levels were determined by a quantitative RT-PCR method.

RESULT

Levels of HDAC5 and CREB mRNA were significantly higher in drug-free depressive patients than those of controls and the higher mRNA levels decreased to control levels after 8-week paroxetine treatment. There were positive correlation between levels of HDAC5 and CREB.

CONCLUSION

Our results suggest the alteration of HDAC5 and CREB gene expression in the systemic pathophysiology of major depression.

Reboxetine and cytochrome P450--comparison with paroxetine treatment in humans

OBJECTIVES

The noradrenaline-selective antidepressant reboxetine in vitro is a weak inhibitor of both cytochrome P450 (CYP) 2D6 and CYP3A4. Thus, in this study the pharmacokinetics of reboxetine in relation to pharmacogenetics and the effects of reboxetine compared to paroxetine treatment on the CYP2D6 and CYP3A4 phenotype were analyzed in healthy control subjects.

METHODS

Healthy male volunteers were treated with either 6 mg reboxetine (n = 26) or 30 mg paroxetine (n = 25). On Days 10/11 of treatment, serum concentrations of the antidepressants were measured and pharmacokinetic parameters calculated. Volunteers were phenotyped at the end of treatment and after at least 3 weeks washout (true phenotype) using 30 mg dextromethorphan (DM) hydrobromide given orally and measuring DM and metabolites in serum 2 h after intake. CYP2D6 and CYP2C19 genotypes were determined in parallel.

RESULTS AND CONCLUSION

Reboxetine serum concentrations showed no correlation with the CYP2D6 genotype and the CYP2D6 phenotype, whereas paroxetine concentrations showed some dependence on CYP2D6. In contrast to in vitro investigations, indicating a major role of CYP3A4 in reboxetine metabolism, reboxetine concentrations in serum showed no correlation with the respective DM metabolic ratios. There was also no correlation between paroxetine concentrations and the CYP3A4 phenotype data. The CYP2C19 genotype (only heterozygosity) had no influence on reboxetine and paroxetine pharmacokinetics. There were only minor changes in the DM metabolite pattern on treatment with reboxetine and no evidence of enzyme inhibition was obtained. In contrast and as expected, paroxetine strongly inhibited CYP2D6. Thus, reboxetine treatment has no effect on the CYP2D6 genotype and no clinically relevant drug interactions involving CYP2D6 are anticipated.

Quantification of striatal dopamine transporters with 123I-FP-CIT SPECT is influenced by the selective serotonin reuptake inhibitor paroxetine: a double-blind, placebo-controlled, crossover study in healthy control subjects

Dopamine transporter (DAT) imaging with (123)I-FP-CIT ((123)I-N-omega-fluoropropyl-2beta-carbomethoxy-3beta-(4-iodophenyl)nortropane) SPECT is frequently used to detect loss of nigrostriatal cells in parkinsonism. Recent (123)I-beta-CIT ((123)I-2beta-carbomethoxy-3beta-(4-iodophenyl)tropane) studies have shown a significant increase in striatal-to-nonspecific beta-CIT binding ratios after treatment with selective serotonin reuptake inhibitors (SSRIs). Due to similarities between (123)I-beta-CIT and (123)I-FP-CIT (both are derived from cocaine and show relatively high affinity for the DAT and the serotonin transporter [SERT]), we hypothesized that quantification of striatal (123)I-FP-CIT binding may be influenced by SSRIs. Moreover, we hypothesized that (123)I-FP-CIT in humans binds not only to DATs but also to central and peripheral SERTs.

METHODS

To study the influence of the SSRI paroxetine on (123)I-FP-CIT binding to DATs in the striatum, we conducted a double-blind, placebo-controlled, crossover study with paroxetine in 8 healthy young male control subjects. In addition, we studied whether paroxetine was able to block (123)I-FP-CIT binding in SERT-rich brain areas and in lung tissue, as lung tissue contains a considerable amount of SERTs. Participants were pretreated for 2 d with paroxetine (20 mg/d) or placebo at 2 sessions (crossover design), and brain SPECT was performed 1 and 3 h after (123)I-FP-CIT injection, whereas lung uptake was measured 2 h after injection.

RESULTS

Compared with placebo pretreatment, we found after paroxetine pretreatment a statistically significant increase (approximately 10%) in specific striatal-to-nonspecific (123)I-FP-CIT binding ratios at 3 h after injection, a time point at which striatal (123)I-FP-CIT binding ratios are stable. In addition, after paroxetine treatment, statistically significantly lower binding ratios were found in SERT-rich brain areas (e.g., at 1 h after injection, midbrain-to-cerebellar ratios were approximately 90% lower) as well as significantly lower uptake in lung tissue was found (approximately 40% lower after paroxetine).

CONCLUSION

In this study we show that the quantification of striatal (123)I-FP-CIT binding to DAT is significantly increased by the SSRI paroxetine in humans. To our knowledge, this is the first study which shows that (123)I-FP-CIT binds in vivo in humans not only to DATs but also to central SERTs and SERTs in lung tissue.

Determination of paroxetine in human saliva by reversed-phase high-performance liquid chromatography with UV detection

A rapid and sensitive high-performance liquid chromatographic method was validated and described for determination of paroxetine in human saliva. Following liquid-liquid extraction of the drug and an internal standard (dibucaine), chromatographic separation was accomplished using a C18 analytical column with a mobile phase consisting of 0.05 mol/L sodium phosphate buffer, pH 5.0, and acetonitrile (A 30:70, v/v; B 60:40, v/v). Paroxetine and the internal standard were detected by ultraviolet absorbance at 205 nm. The average recoveries of the drug and internal standard were 92.5% and 89%, respectively. The lower limits of detection and quantification were 1 and 4 ng/ml, respectively, and the calibration curve was linear over a concentration range of 4 ng/ml. The saliva level of paroxetine in patients with depression taking 10 to 40 mg/day of the drug was significantly correlated with the plasma level of paroxetine in each patient (r = 0.617, P < 0.004, n = 19). These data indicate that the saliva level of paroxetine could be a useful marker to predict the plasma level of the drug.

High Plasma Concentrations of Paroxetine Impede Clinical Response in Patients With Panic Disorder

Selective serotonin reuptake inhibitors are thought to interact with serotonergic neurons and be effective for treatment of panic disorder. In the present study, the authors investigated an association between plasma concentrations of paroxetine in patients with panic disorder and clinical response to initial treatment with paroxetine. Subjects were 21 unrelated Japanese patients who fulfilled DSM-IV-TR criteria for a diagnosis of panic disorder (6 males, 15 females, mean age 35.9 +/- 11.3 years). Subjects were administered 10 mg/day of paroxetine for 2 weeks as initial treatment. Improvement of the symptoms of the disorder was assessed with the Panic and Agoraphobia Scale (PAS). In the range of plasma levels >20 ng/mL, none of the subjects showed the reduction ratio in PAS score >0.2. The subjects whose plasma concentrations of paroxetine were less than 20 ng/mL had a significantly higher mean reduction ratio in PAS score than the subjects whose plasma concentrations of paroxetine were >20 ng/mL. Multiple regression analysis showed that the plasma concentration of paroxetine was the only significant factor and accounted for 28.0% of the variability in the reduction ratio of PAS score of the subjects. The final model of correlation was: reduction ratio in PAS score = 0.423 - 0.009 x (plasma concentrations of paroxetine) (R = 0.529, P = 0.014, coefficient of determination (R2) = 0.280). Assuming that the reduction ratio in PAS score was 0.2 in the equation above, plasma concentration of paroxetine is calculated to be about 25 ng/mL, which is suggested to be the upper end of the therapeutic window for the initial phase of the treatment with paroxetine for panic disorder.

Effect of paroxetine on enhanced contextual fear induced by single prolonged stress in rats

RATIONALE

Single prolonged stress (SPS) is an animal model of posttraumatic stress disorder (PTSD) that can reproduce enhanced hypothalamo-pituitary-adrenal negative feedback.

OBJECTIVES

We examined whether SPS can produce an enhanced psychophysiological reactivity to laboratory stressors unrelated to trauma and whether paroxetine (PRX) can alleviate the enhanced anxiety and fear response in rats subjected to SPS. Furthermore, the effect of PRX on pain sensitivity was examined in rats with and without SPS.

METHODS

Rats were subjected to SPS (restraint for 2 h, forced swim for 20 min, and ether anesthesia) and then kept undisturbed for 14 days. After that, contextual fear response was assessed. Twenty-four hours after foot shock conditioning, freezing behavior was measured during reexposure to the shock environment for 3 min. Pain sensitivity was assessed by the flinch-jump test. PRX (0.01, 0.03, or 0.1 mg/mL) was chronically administered orally in drinking water.

RESULTS

Rats subjected to SPS showed a significant increase in contextual freezing compared to rats without SPS. Chronic administration of PRX at concentrations of 0.03 and 0.1 mg/mL (which produced serum concentrations similar to those that are clinically relevant) caused significant suppression of the enhanced contextual freezing. Acute administration of PRX at a dose producing clinically relevant serum concentrations did not affect the enhanced freezing.

CONCLUSIONS

Our results suggest that SPS can reproduce behavioral alteration similar to that observed in patients with PTSD, and this elevated fear response can be alleviated by the chronic administration of PRX at doses producing clinically relevant serum concentrations.

Serotonin transporter occupancy induced by paroxetine in patients with major depression disorder: a 123I-ADAM SPECT study

RATIONALE

To assess the paroxetine-induced serotonin transporter (SERT) occupancy (SERTocc) using in vivo (123)I-ADAM SPECT.

OBJECTIVES

(123)I-ADAM SPECT was used to investigate the SERTocc induced by paroxetine in major depression disorder (MDD) patients, to compare the SERT availability in drug-free MDD patients and healthy volunteers, and to study the relationship between paroxetine plasma concentrations (Cp) and SERTocc.

MATERIALS AND METHODS

Measures of SERT availability by means of (123)I-ADAM SPECT were obtained in ten MDD patients before and after 4- to 6-week treatment with paroxetine 20 mg/day. (123)I-ADAM SPECT measures of SERT availability from a group of ten previously studied age-matched healthy volunteers were used for comparison. The relationship between percentages of SERTocc and paroxetine Cp was studied using an E (max) model.

RESULTS

Mean SERTocc values were 66.4 +/- 9.5% in midbrain, 63.0 +/- 9.6% in thalamus, and 61.3 +/- 10.9% in striatum. No significant differences in SERTocc were found among these three regions. No significant differences in mean SERT availability were found in any region between drug-free MDD patients (midbrain = 1.14 +/- 0.15; thalamus = 0.85 +/- 0.13; striatum = 0.70 +/- 0.07) and healthy volunteers (midbrain = 1.19 +/- 0.22; thalamus = 0.96 +/- 0.14; striatum = 0.67 +/- 0.15). The E (max) model returned a SERTocc(max) = 70.5% and a Cp(50) = 2.7 ng/ml.

CONCLUSIONS

Using (123)I-ADAM SPECT, treatment with paroxetine 20 mg/day leads to more than 60% SERTocc on average in cerebral regions with known high SERT density. Data from this study do not support the existence of SERT availability differences between drug-free MDD patients and healthy volunteers. Finally, the E (max) model is suitable for the study of paroxetine Cp relationship to (123)I-ADAM SPECT-measured SERTocc. This approach may be useful for pharmacokinetic-pharmacodynamic relationships in drug development.

Terbinafine increases the plasma concentration of paroxetine after a single oral administration of paroxetine in healthy subjects

OBJECTIVE

Paroxetine is believed to be a substrate of CYP2D6. However, no information was available indicating drug interaction between paroxetine and inhibitors of CYP2D6. The aim of this study was to examine the effects of terbinafine, a potent inhibitor of CYP2D6, on pharmacokinetics of paroxetine.

METHODS

Two 6-day courses of either a daily 150-mg of terbinafine or a placebo, with at least a 4-week washout period, were conducted. Twelve volunteers took a single oral 20-mg dose of paroxetine on day 6 of both courses. Plasma concentrations of paroxetine were monitored up to 48 h after dosing.

RESULTS

Compared with the placebo, terbinafine treatment significantly increased the peak plasma concentration (C(max)) of paroxetine, by 1.9-fold (6.4 +/- 2.4 versus 12.1 +/- 2.9 ng/ml, p < 0.001), and the area under the plasma concentration-time curve from zero to 48 h [AUC (0-48)] of paroxetine by 2.5-fold (127 +/- 67 vs 318 +/- 102 ng/ml, p < 0.001). Elimination half-life differed significantly (15.3 +/- 2.4 vs 22.7 +/- 8.8 h, p < 0.05), although the magnitude of alteration (1.4-fold) was smaller than C(max )or AUC.

CONCLUSION

The present study demonstrated that the metabolism of paroxetine after a single oral dose was inhibited by terbinafine, suggesting that inhibition of CYP2D6 activity may lead to a change in the pharmacokinetics of paroxetine. However, further study is required to confirm this phenomenon at steady state.

Dose-response relationship of duloxetine in placebo-controlled clinical trials in patients with major depressive disorder

RATIONALE

The optimal dose for achieving the maximum antidepressive effect of selective serotonin reuptake inhibitors (SSRIs) or serotonin-noradrenalin reuptake inhibitors (SNRIs) remains a controversial issue. The varying sensitivity of scales that measure the severity of depression is one of the many factors affecting the evaluation of the dose-response relationship with antidepressants.

OBJECTIVES

To determine if the 6-item Hamilton rating scale for depression (HAM-D6) demonstrates a clearer association between dose and antidepressive effect compared with the 17-item Hamilton rating scale for depression (HAM-D17) for fixed doses of duloxetine hydrochloride (40, 60, 80, and 120 mg daily) from six double-blind, randomized, placebo-controlled clinical trials assessing safety and efficacy in the acute treatment of patients with DSM-IV-defined major depressive disorder (MDD).

METHODS

Mantel-Haenszel adjusted effect sizes were determined by dose for change from baseline to endpoint in HAM-D6 and HAM-D17 scores from the six studies. To confirm, assessments were repeated on the subset of the population corresponding to the 70% of patients with the longest duration of treatment regardless of study, treatment, dose, geography, or completion status.

RESULTS

For the majority of assessments, HAM-D6 effect sizes were numerically larger than those estimated from the HAM-D17. Findings support that duloxetine 60 mg daily is the best effective dose.

CONCLUSIONS

In this assessment of patients with MDD, the HAM-D6 was shown to be more sensitive compared with the HAM-D17 at detecting treatment effects. These findings are consistent with published results of other effective antidepressants.

Alteration of decreased plasma NO metabolites and platelet NO synthase activity by paroxetine in depressed patients

Although major depression (MD) and cardiovascular disease (CVD) have been conclusively linked in the literature, the mechanism associating MD and CVD is yet undetermined. The purpose of this paper is to further investigate a potential mechanism involving nitric oxide (NO) and to examine the effect of the selective serotonin reuptake inhibitor paroxetine on NO production by both platelets and the endothelium. In total, 17 subjects with MD and 12 healthy controls (HCs) with no known history of cardiovascular illness completed the study. Paroxetine was administered to both the MD patients and HCs over an 8-week period, and then medication was discontinued. Blood samples were taken at various times throughout paroxetine treatment and after discontinuation. Plasma NO metabolite (NOx) levels were measured by a chemiluminescence method. Platelet endothelial NO synthase (eNOS) activity was examined through the conversion of L-[14C]arginine to L-[(14)C]citrulline. Data were analyzed using t-tests and a linear mixed effects model. Baseline levels of both plasma NOx and platelet NOS activity were significantly lower in subjects with MD compared to HCs. Throughout paroxetine treatment, plasma NOx levels increased in both HCs and MD patients. However, platelet eNOS activity decreased in HCs, while no statistically significant change was evidenced in MD patients. These data suggest that, in MD patients, decreased peripheral production of NO, a potential contributor to increased cardiovascular risk, is modified by administration of the antidepressant paroxetine.

Risperidone in the treatment of psychotic depression

In the preset study, the authors investigated that effects of the antipsychotic drug risperidone on psychotic depression and examined the mechanism of risperidone to ameliorate psychotic depression. Fifteen patients met the DSM-IV criteria for major depressive disorder with psychotic features and the remaining five patients met those for bipolar I disorder (most recent episode depressed) with psychotic features (M/F: 8/12, age: 54+/-18). All patients were evaluated regarding their clinical improvement using the Hamilton Rating Scale for Depression (Ham-D), and Positive and Negative Syndrome Scale (PANSS). In addition, plasma concentrations of HVA and MHPG were analyzed by HPLC. Patients with a 50% or more improvement in Ham-D score were defined as responders. Three were prescribed risperidone alone, and the other 17 were administered risperidone as an addition to preexisting antidepressants or mood stabilizers. The preexisting antidepressants or mood stabilizers were as follows: paroxetine (6), lithium (3), valproic acid (3), clomipramine (2), fluvoxamine (1), amitriptyline (1), amoxapine (1). The average dose of risperidone was 1.8+/-0.5 mg/day. Eleven of twenty patients (55%) turned out to be responders 4 weeks after initiation of risperidone administration. No differences were observed between responders and nonresponders with respect to age, sex, Ham-D score before risperidone treatment, dose and plasma level of risperidone or its active metabolite, 9-hydroxyrisperidone. Plasma HVA levels before risperidone administration in responders were significantly higher than those in nonresponders. In addition, a significant correlation was observed between changes in plasma HVA level and the percentage improvement on Ham-D score. These results indicate that treatment with risperidone is effective to ameliorate psychotic depression, and the influence of risperidone on dopaminergic activity is associated with its efficacy.

The impact of CYP2D6 genotypes on the plasma concentration of paroxetine in Japanese psychiatric patients

The authors investigated the impact of the CYP2D6 genotypes on the plasma concentration of paroxetine (PAX) in 55 Japanese psychiatric patients. They were administered 10 to 40 mg/day (24+/-10.0 mg/day) of PAX and maintained at the same daily dose for at least two weeks to obtain the steady-state concentrations. The plasma levels of PAX were 15.8+/-15.0, 47.4+/-32.0, 101.2+/-59.9 and 177.5+/-123.6 ng/ml at the daily dose of 10, 20, 30 and 40 mg, respectively, which suggested dose dependent kinetics of PAX. The allele frequencies of the CYP2D65, CYP2D610 and CYP2D641 were 1.8%, 41.8% and 1.8%, respectively. Significantly higher PAX concentrations were observed in the patients having one functional allele compared with those with two functional alleles (150.9+/-20.6 vs. 243.6+/-25.2 ng/ml mg(-1) kg(-1), p<0.05, Newman-Keuls multiple comparison test) or no functional (243.6+/-25.2 vs. 76.7+/-6.1 ng/ml mg(-1) kg(-1), p<0.05, Newman-Keuls multiple comparison test) in the subjects with 30 mg/day of paroxetine. The same trend of findings as in the subjects treated with 30 mg/day were observed in the subjects with 40 mg/day of PAX. The present results suggest that having one non-functional allele is the marker for high plasma concentration of PAX when relatively high daily dose of PAX is administered.