Dose Of Paroxetine Research Articles

Impact of CYP2D6 Genotype on Paroxetine Serum Concentration.

Paroxetine is a selective serotonin reuptake inhibitor metabolized by cytochrome P450 (CYP)2D6. Only small-scale studies have reported the impact of CYP2D6 genotype on paroxetine exposure, and international guidelines differ in their recommendations on whether paroxetine should be administered according to CYP2D6 genotype. To clarify this issue, the aim of the present study was to investigate the impact of CYP2D6 genotype on paroxetine serum concentration in a large population of patients after adjusting for CYP2C19 genotype, age, and sex. Patients from a therapeutic drug monitoring database with records on their paroxetine serum concentrations and CYP2D6 and CYP2C19 genotyping between 2010 and 2021 were included in the study. The impact of CYP2D6 and CYP2C19 genotypes, age, and sex on the paroxetine concentration-to-dose (C/D) ratio was investigated by multiple linear regression analysis. Patients treated with relevant CYP inhibitors or inducers were excluded. In total, 304 patients were included in the study: 17 CYP2D6 poor metabolizers (PMs), 114 intermediate metabolizers (IMs), 168 extensive metabolizers (EMs), and 5 ultrarapid metabolizers. Multiple linear regression analysis showed that CYP2D6 IMs and PMs had 2.2-fold and 3.8-fold higher paroxetine C/D-ratios than extensive metabolizers, respectively ( P < 0.001). Patients who were CYP2C19 IMs (n = 70) or PMs (n = 13) had 1.6-fold higher paroxetine C/D ratio than extensive metabolizers ( P = 0.04). An age ≥65 years was associated with a 2.9-fold increased C/D ratio ( P < 0.001), whereas sex was not significantly associated with paroxetine exposure. The present study showed that CYP2D6 genotype is of significant importance for paroxetine dose adjustments. For CYP2D6 PMs, 25% of the regular paroxetine starting dose may be sufficient, whereas CYP2D6 IMs could receive 50% of the regular dosage. This well-powered study shows that the guidelines should consider the importance of CYP2D6 genotype for personalized dosing of paroxetine.

SSRI antidepressants differentially modulate serotonin reuptake and release in Drosophila.

Selective serotonin reuptake inhibitor (SSRI) antidepressants are commonly prescribed treatments for depression, but their effects on serotonin reuptake and release are not well understood. Drosophila melanogaster, the fruit fly, expresses the serotonin transporter (dSERT), the major target of SSRIs, but real-time serotonin changes after SSRIs have not been characterized in this model. The goal of this study was to characterize effects of SSRIs on serotonin concentration and reuptake in Drosophila larvae. We applied various doses (0.1-100 μM) of fluoxetine (Prozac), escitalopram (Lexapro), citalopram (Celexa), and paroxetine (Paxil), to ventral nerve cord (VNC) tissue and measured optogenetically-stimulated serotonin release with fast-scan cyclic voltammetry (FSCV). Fluoxetine increased reuptake from 1 to 100 μM, but serotonin concentration only increased at 100 μM. Thus, fluoxetine occupies dSERT and slows clearance but does not affect concentration. Escitalopram and paroxetine increased serotonin concentrations at all doses, but escitalopram increased reuptake more. Citalopram showed lower concentration changes and faster reuptake profiles compared with escitalopram, so the racemic mixture of citalopram does not change reuptake as much as the S-isomer. Dose response curves were constructed to compare dSERT affinities and paroxetine showed the highest affinity and fluoxetine the lowest. These data demonstrate SSRI mechanisms are complex, with separate effects on reuptake or release. Furthermore, dynamic serotonin changes in Drosophila are similar to previous studies in mammals. This work establishes how antidepressants affect serotonin in real-time, which is useful for future studies that will investigate pharmacological effects of SSRIs with different genetic mutations in Drosophila.

Metabolomics reveals biomarkers in human urine and plasma to predict cytochrome P450 2D6 (CYP2D6) activity.

Background and PurposeIndividualized assessment of cytochrome P450 2D6 (CYP2D6) activity is usually performed through phenotyping following administration of a probe drug to measure the enzyme's activity. To avoid any iatrogenic harm (allergic drug reaction, dosing error) related to the probe drug, the development of non‐burdensome tools for real‐time phenotyping of CYP2D6 could significantly contribute to precision medicine. This study focuses on the identification of markers of the CYP2D6 enzyme in human biofluids using an LC‐high‐resolution mass spectrometry‐based metabolomic approach.Experimental ApproachPlasma and urine samples from healthy volunteers were analysed before and after intake of a daily dose of paroxetine 20 mg over 7 days. CYP2D6 genotyping and phenotyping, using single oral dose of dextromethorphan 5 mg, were also performed in all participants.Key ResultsWe report four metabolites of solanidine and two unknown compounds as possible novel CYP2D6 markers. Mean relative intensities of these features were significantly reduced during the inhibition session compared with the control session (n = 37). Semi‐quantitative analysis showed that the largest decrease (−85%) was observed for the ion m/z 432.3108 normalized to solanidine (m/z 398.3417). Mean relative intensities of these ions were significantly higher in the CYP2D6 normal–ultrarapid metabolizer group (n = 37) compared with the poor metabolizer group (n = 6). Solanidine intensity was more than 15 times higher in CYP2D6‐deficient individuals compared with other volunteers.Conclusion and ImplicationsThe applied untargeted metabolomic strategy identified potential novel markers capable of semi‐quantitatively predicting CYP2D6 activity, a promising discovery for personalized medicine.

A Case Report of Sleep-Related Painful Erection Successfully Treated with Paroxetine

Sleep-Related Painful Erection (SRPE) is a rare condition characterized by recurrent, painful penile erections occurring when awakening from the Rapid Eye Movement (REM) sleep stage. The cause of SRPE is still unknown, the therapeutic strategies still in an expert-based opinion phase and there is no consensus yet. We present a case of a 23-year-old patient suffering from SRPE for 1 year, the smart bracelet which has a sleep monitoring function showed his sleep was fragmented by awakenings at the end of all the REM period. Several treatments such as tamsulosin and highfrequency hyperthermia therapy and Chinese herbal medicine did not prompt any improvement of his condition, but after taking a single daily dose of paroxetine 20mg for twelves weeks, both the frequency and intensity of SRPE gradually decreased. Even though the antidepressants to which paroxetine belongs were included as one of the abandoned treatments in recent review, in our case, paroxetine showed a long-term and stable effect on patients with SRPE, it indicates that the therapeutic effect of paroxetine on SRPE deserves further study and observation.

Effects of paroxetine on the pharmacokinetics of atomoxetine and its metabolites in different CYP2D6 genotypes.

The aim of this study was to investigate the effects of paroxetine, a potent inhibitor of CYP2D6, on the pharmacokinetics of atomoxetine and its two metabolites, 4-hydroxyatomoxetine and N-desmethylatomoxetine, in different CYP2D6 genotypes. Twenty-six healthy subjects were recruited and divided into CYP2D6*wt/*wt (*wt=*1 or *2, n = 10), CYP2D6*wt/*10 (n = 9), and CYP2D6*10/*10 groups (n = 7). In atomoxetine phase, all subjects received a single oral dose of atomoxetine (20mg). In paroxetine phase, after administration of a single oral dose of paroxetine (20mg) for six consecutive days, all subjects received a single oral dose of atomoxetine with paroxetine. Plasma concentrations of atomoxetine and its metabolites were determined up to 24 h after dosing. During atomoxetine phase, there were significant differences in Cmax and AUC0-24 of atomoxetine and N-desmethylatomoxetine among three genotype groups, whereas significant differences were not found in relation to CYP2D6*10 allele after administration of paroxetine. AUC ratios of 4-hydroxyatomoxetine and N-desmethylatomoxetine to atomoxetine were significantly different among three genotype groups during atomoxetine phase (all, P < 0.001), but after paroxetine treatment significant differences were not found. After paroxetine treatment, AUC0-24 of atomoxetine was increased by 2.3-, 1.7-, and 1.3-fold, in CYP2D6*wt/*wt, CYP2D6*wt/*10, and CYP2D6*10/*10 groups in comparison to atomoxetine phase, respectively. AUC ratio of 4-hydroxyatomoxetine to atomoxetine in each group was significantly decreased, whereas AUC ratio of N-desmethylatomoxetine to atomoxetine significantly increased after administration of paroxetine. In conclusion, paroxetine coadministration significantly affected pharmacokinetic parameters of atomoxetine and its two metabolites, 4-hydroxyatomoxetine and N-desmethylatomoxetine. When atomoxetine was administered alone, Cmax, AUC0-24 and CL/F of atomoxetine were significantly different among the three CYP2D6 genotype groups. However, after paroxetine coadministration, no significant differences in these pharmacokinetic parameters were observed among the CYP2D6 genotype groups.

The Synergistic Combination of Everolimus and Paroxetine Exerts Post-ischemic Neuroprotection In Vitro.

Ischemic stroke is a debilitating multi-factorial cerebrovascular disorder, representing an area of tremendous unmet medical need. Combination treatment has been proposed as a promising therapeutic approach towards combating ischemic stroke. The present study employs in vitro oxygen glucose deprivation (OGD) model to evaluate the post-ischemic neuroprotective efficacy of Everolimus and Paroxetine, alone and in combination. Post-OGD treatment with Everolimus and Paroxetine, alone or in combination, significantly improved the cell survival (~ 80%) when compared to the cells subjected to ischemic injury alone. The individual neuroprotective doses of Everolimus and Paroxetine were found to be at 6.25 and 25nM, respectively. Whereas, the synergistic neuroprotective dose for Everolimus:Paroxetine was 2:10nM, calculated using theChou-Talalay combination index and other four mathematical models. The synergistic combination dose downregulated neuroinflammatory genes (Tnf-α, Il1b, Nf-κB, and iNos) and upregulated the neuroprotective genes (Bcl-2, Bcl-xl, Hif-1, and Epo). The mitochondrial functioning and ROS neutralizing ability increased with combination treatment. Further, the active role of nitric oxide synthase and calmodulin were revealed while exploring the bio-activity of Everolimus and Paroxetine through network pharmacology. The present study for the first time demonstrates the synergistic post-ischemic neuroprotective efficacy of combination treatment with Everolimus and Paroxetine in vitro. Taken together, these findings clearly suggest that Everolimus in combination with Paroxetine may represent a promising therapeutic strategy for the treatment of ischemic stroke, further supporting the combination treatment strategy for this debilitating disorder.

Laxative use and clinical correlates in hospitalized patients with obsessive-compulsive disorder: a retrospective descriptive study.

BackgroundConstipation is a common clinical problem with insufficient attention. Medication-emergent constipation is a rarely studied adverse reaction in patients with obsessive-compulsive disorder (OCD).MethodsIn this descriptive study, we retrospectively investigated the prevalence of laxative use and its relationship with clinical characteristics in hospitalized OCD patients. A total of 51 OCD patients were included in the final analysis.ResultsThe proportion of patients using laxatives was 31.4%, and the commonly used laxatives were phenolphthalein tablet, lactulose and congrongtongbian oral liquid (a patent herbal medicine). In the laxative group, hospital stays were longer when compared to the nonlaxative group. Moreover, the dose of paroxetine was higher in patients treated with laxatives than in those without laxative use. Correlation analysis indicated that laxative use was positively associated with hospital stays, as well as the dose of paroxetine.ConclusionThe current study provided a preliminary picture of constipation and laxative use in hospitalized OCD patients. Close monitoring and treatment of constipation are recommended in OCD patients with pharmacotherapy.

Comparative effectiveness of switching paroxetine formulation for treatment of major depressive disorder: an open-label multicenter study.

AimTo assess the effectiveness and safety of switching the antidepressant formulation from immediate-release (IR) to controlled-release (CR) paroxetine in patients with major depressive disorder (MDD).Patients and methodsA total of 113 outpatients with MDD diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision, and treated with a stable dose of IR paroxetine for at least 6 months were enrolled. Patients were then switched to CR paroxetine for 8 weeks. Effectiveness was evaluated by scores on the Himorogi Self-Rating Depression/Anxiety Scales (HSDS/HSAS) and the Clinical Global Impression – Severity (CGI-S). Safety was evaluated based on the reported adverse drug reactions (ADRs). Medication satisfaction and preference were assessed based on questionnaire responses using Likert-type scales.ResultsThe overall patient HSDS/HSAS scores significantly improved after switching from IR to CR paroxetine (P<0.001). Furthermore, CR paroxetine was superior to IR paroxetine (P<0.001) according to the results of the CGI-S evaluation. ADRs were experienced by 14 (12.4%) patients, including dry mouth, nausea/vomiting, somnolence/drowsiness, and wakefulness/arousal during sleep. Satisfaction and preference for paroxetine improved after switching to the CR formulation (P<0.001; chi-square test).ConclusionThese results suggest that switching the treatment from IR to CR paroxetine could improve depressive symptoms and decrease ADRs. However, these results may have been caused by the psychological effect of drug switching. Hence, future studies with blinded evaluation methods are required to confirm and expand our findings.

04 A Comparative Study Between Two Different Doses of Dapoxetine and a Single Dose of Paroxetine on Demand in the Treatment of Cases of Premature Ejaculation

04 A Comparative Study Between Two Different Doses of Dapoxetine and a Single Dose of Paroxetine on Demand in the Treatment of Cases of Premature Ejaculation

422 A Comparative Study between Two Different Doses of Dapoxetine and a Single Dose of Paroxetine on Demand in the Treatment of Cases of Premature Ejaculation

422 A Comparative Study between Two Different Doses of Dapoxetine and a Single Dose of Paroxetine on Demand in the Treatment of Cases of Premature Ejaculation

Effects of antidepressants on P2X7 receptors

Antidepressants including paroxetine, fluoxetine and desipramine are commonly used for treating depression. P2×7 receptors are member of the P2X family. Recent studies indicate that these receptors may constitute a novel potential target for the treatment of depression. In the present study, we examined the action of these antidepressants on cloned rat P2×7 receptors that were stably expressed in human embryonic kidney (HEK) 293 cells by using the whole-cell patch-clamp technique, and found that paroxetine at a dose of 10µM could significantly reduce the inward currents evoked by the P2×7 receptors agonist BzATP by pre-incubation for 6–12 but not by acute application (10µM) or pre-incubation for 2–6h at a dose of 1µM, 3µM or 10µM paroxetine. Neither fluoxetine nor desipramine had significant effects on currents evoked by BzATP either applied acutely or by pre-incubation at various concentrations. These results suggest that the sensitivity of rat P2×7 receptors to antidepressants is different, which may represent an unknown mechanism by which these drugs exert their therapeutic effects and side effects.

Pharmacokinetics of Paroxetine Tablets in healthy Arabic Subjects

A single oral dose of paroxetine 20 mg tablets (Seroxat®, GlaxoSmithKline, England) were administered to thirty six healthy male adult fasting subjects to study the pharmacokinetics of the drug in Arabic population.&#x0D; Twenty blood samples were obtained from each subject up to 96 hours after dosing. The concentrations of paroxetine were monitored in plasma to calculate the pharmacokinetic parameters; Cmax, Tmax, AUC0-t,AUC0-¥,Kel&amp; T0.5;applying non-compartmental analysis.&#x0D; The mean±SD for the abovementioned parameters were; 3.14±2.09 ng/ml, 5.1±1.28 hr, 48.6±45.9 ng.hr/ml, 59.5±42.3 ng.hr/ml, 0.066±0.022 hr-1 and 11.9±5.1 hrs, respectively. The present investigation demonstrated high inter individual variation particularly in the primary pharmacokinetic parameters Cmax (CV=66.5%), AUC0-t (CV=94.5%), and AUC0-¥ (CV=71%). Beside, comparing the results of the current investigation obtained from Arabic population with that published in other studies conducted in other nations indicating that there is clear population variability in the pharmacokinetic of paroxetine.&#x0D; Therefore, it can be concluded from the present investigation that individualization and therapeutic drug monitoring are suggested for optimal therapy with paroxetine. However, further investigations are recommended to confirm this suggestion by studying the pharmacokinetics of the drug in Arabic patients and after multiple dosing.

Items of the Montgomery-Åsberg Depression Rating Scale Associated With Response to Paroxetine Treatment in Patients With Major Depressive Disorder.

In the present study, we investigated the association between the severity of each symptom evaluated by the Montgomery-Åsberg Depression Rating Scale (MADRS) at baseline and responsiveness to treatment in patients with major depressive disorder (MDD) to identify the items that predict treatment response. The patients received a diagnosis of MDD if they had a score greater than 20 points on the MADRS. Following admission, 120 patients were enrolled in the study, and 89 patients completed the study. For the first week, a 20-mg/d dose of paroxetine was administered; thereafter, the dose was increased to 40 mg/d. The MADRS was applied at baseline and after 1, 2, 4, and 6 weeks. We defined responders as patients with improvements in their MADRS scores of more than 50% after 6 weeks of treatment. A multiple regression analysis of MADRS scores at 6 weeks was performed to identify patients who responded to treatment. There was a significant difference between responders and nonresponders in the reported sadness (RS) score for all MADRS items. In the multiple logistic regression analysis, only the RS and concentration difficulties (C) scores showed a significant association with treatment response. Based on the results of χ tests, RS score cutoff values of 2/3 and 3/4 revealed significant differences in the responder rate. None of the cutoff values for the C score revealed significant differences. The RS score was significantly associated with responsiveness to paroxetine treatment for MDD, with higher RS scores predicting poor responses to treatment.

Tailored therapy for the refractory GERD patients by combined multichannel intraluminal impedance-pH monitoring.

About 30% of patients with gastroesophageal reflux disease (GERD) are refractory to proton pump inhibitor (PPI). The reason for the PPI failure in Asian GERD patients has rarely been studied, and the therapy remained unclear. The aims were to explore the possible reasons for PPI failure and to treat these patients with the guidance of 24-h multichannel intraluminal impedance-pH (MII-pH) monitoring. Thirty-nine consecutive patients with refractory GERD were enrolled; 24-h MII-pH monitoring was performed on PPI. The refractory GERD patients were grouped into acid overexposure, non-acid reflux, and functional heartburn after the MII-pH monitoring. Double dose of either PPI or paroxetine was administered to refractory GERD patients within different groups. The number of patients in groups of acid overexposure, non-acid reflux, and functional heartburn was 6, 12, and 21, respectively. The acid overexposure group had the most acid reflux events. Among the acid overexposure group, five (5/6) patients accomplish symptom relief with double dose of esomeprazole. For the patients in non-acid reflux group, double dose of esomeprazole made half (6/12) of the patients obtain symptom relief. For the patients in functional heartburn group, the paroxetine had relieved the symptoms in 14 patients among all the 21 patients. In total, with the guidance of MII-pH monitoring, 64.1% (25/39) of refractory GERD patients accomplished symptom relief. Acid overexposure, non-acid reflux, and functional heartburn were the common reasons for persistent reflux symptoms despite PPI. With the guidance of MII-pH, a tailored therapy could resolve the persistent reflux symptoms among two-third of patients.

Effects of Paroxetine, a CYP2D6 Inhibitor, on the Pharmacokinetic Properties of Hydrocodone After Coadministration With a Single-entity, Once-daily, Extended-release Hydrocodone Tablet

PurposeA single-entity, once-daily, extended-release formulation of hydrocodone bitartrate (HYD) has been developed for the management of moderate to severe chronic pain. Hydrocodone undergoes cytochrome P-450 (CYP)-mediated metabolism involving the CYP3A4 and CYP2D6 isozymes. CYP3A4 yields norhydrocodone, a major inactive metabolite, whereas CYP2D6 yields hydromorphone, a minor active metabolite. This study examined the influence of the coadministration of paroxetine, a strong selective CYP2D6 inhibitor, on the pharmacokinetic properties of hydrocodone (and hydromorphone) in healthy adults. MethodsIn this randomized, double-blind, 2-period, 2-treatment crossover study, 24 healthy subjects received paroxetine 20 mg or placebo once daily for 12 days and an HYD 20-mg tablet on day 10 of each period. FindingsHydrocodone mean Cmax and t½ and median Tmax values were similar with paroxetine or placebo coadministration (16.8 vs 15.9 ng/mL, 8.5 vs 8.4 hours, and 18.0 vs 18.0 hours, respectively), as were mean AUC0–t and AUC0–∞ values (342.9 vs 325.3 ng · h/mL and 346.3 vs 328.5 ng · h/mL). The 90% CIs of the geometric mean ratios of the hydrocodone AUC and Cmax values were fully within the predetermined range of 80% to 125%, suggesting that there was no effect of multiple doses of paroxetine on systemic exposure to hydrocodone. Mean hydromorphone AUC0–t and Cmax values were decreased with paroxetine versus placebo (0.64 vs 3.8 ng · h/mL and 0.06 vs 0.19 ng/mL), whereas Tmax values remained similar (18.0 vs 16.1 hours, respectively). The mean hydromorphone AUC0–∞ value could not be calculated. Both regimens were well tolerated; after HYD administration, the numbers of adverse events were similar between the 2 treatment regimens, and all adverse events were mild. ImplicationsIn this study, the coadministration of single-dose HYD with paroxetine at steady state did not alter systemic exposure to hydrocodone, suggesting that HYD can be coadministered with CYP2D6 inhibitors at therapeutic doses, without dosage modification.

Differentiated effects of the multimodal antidepressant vortioxetine on sleep architecture: Part 2, pharmacological interactions in rodents suggest a role of serotonin-3 receptor antagonism.

Antidepressants often disrupt sleep. Vortioxetine, a multimodal antidepressant acting through serotonin (5-HT) transporter (SERT) inhibition, 5-HT3, 5-HT7 and 5-HT1D receptor antagonism, 5-HT1B receptor partial agonism, and 5-HT1A receptor agonism, had fewer incidences of sleep-related adverse events reported in depressed patients. In the accompanying paper a polysomnographic electroencephalography (sleep-EEG) study of vortioxetine and paroxetine in healthy subjects indicated that at low/intermediate levels of SERT occupancy, vortioxetine affected rapid eye movement (REM) sleep differently than paroxetine. Here we investigated clinically meaningful doses (80–90% SERT occupancy) of vortioxetine and paroxetine on sleep-EEG in rats to further elucidate the serotoninergic receptor mechanisms mediating this difference. Cortical EEG, electromyography (EMG), and locomotion were recorded telemetrically for 10 days, following an acute dose, from rats receiving vortioxetine-infused chow or paroxetine-infused water and respective controls. Sleep stages were manually scored into active wake, quiet wake, and non-REM or REM sleep. Acute paroxetine or vortioxetine delayed REM onset latency (ROL) and decreased REM episodes. After repeated administration, vortioxetine yielded normal sleep-wake rhythms while paroxetine continued to suppress REM. Paroxetine, unlike vortioxetine, increased transitions from non-REM to wake, suggesting fragmented sleep. Next, we investigated the role of 5-HT3 receptors in eliciting these differences. The 5-HT3 receptor antagonist ondansetron significantly reduced paroxetine’s acute effects on ROL, while the 5-HT3 receptor agonist SR57227A significantly increased vortioxetine’s acute effect on ROL. Overall, our data are consistent with the clinical findings that vortioxetine impacts REM sleep differently than paroxetine, and suggests a role for 5-HT3 receptor antagonism in mitigating these differences.

Requirement of AMPK activation for neuronal metabolic-enhancing effects of antidepressant paroxetine.

Reduced glucose metabolism has been implicated as a pathophysiology of depressive disorder. Normalization of such impaired neurometabolism has been related to the therapeutic actions of antidepressant medication. However, the molecular mechanism underlying the neurometabolic actions of antidepressants has not been fully understood. Given that AMP-activated protein kinase (AMPK) is a master switch for energy homeostasis, we aimed to determine whether selective serotonin reuptake inhibitor paroxetine enhances energy metabolism by activating AMPK in neuroblastoma cells. We found that paroxetine dose dependently increased mitochondrial biogenesis, which involves the AMPK-peroxisome proliferator-activated receptor-γ coactivator-1α pathway. In addition, paroxetine-induced AMPK activation increases glucose uptake and ATP production. These neurometabolic effects of paroxetine were suppressed by cotreatment with compound C (CC), an AMPK inhibitor. These findings suggest a possibility that modulation of the AMPK pathway might be a previously unrecognized mechanism underlying the neurometabolic action of antidepressants. Further study is warranted to examine the region-specific and time-specific effects of AMPK modulation by antidepressants on mood-related behaviors.

A 5-HT3 receptor antagonist potentiates the behavioral, neurochemical and electrophysiological actions of an SSRI antidepressant

More effective treatments for major depression are needed. We studied if the selective 5-HT3 receptor antagonist ondansetron can potentiate the antidepressant potential of the selective serotonin (5-HT) reuptake inhibitor (SSRI) paroxetine using behavioral, neurochemical and electrophysiological methods. Flinders Sensitive Line (FSL) rats, treated with ondansetron, and/or a sub-effective dose of paroxetine, were assessed in the forced swim test. The effects of an acute intravenous administration of each compound alone and in combination were evaluated with respect to 5-HT neuronal firing rate in the dorsal raphe nucleus (DRN). Effects of s.c. administration of the compounds alone and in combination on extracellular levels of 5-HT were assessed in the ventral hippocampus of freely moving rats by microdialysis. The results showed that ondansetron enhanced the antidepressant activity of paroxetine in the forced swim test. It partially prevented the suppressant effect of paroxetine on DRN 5-HT neuronal firing and enhanced the paroxetine-induced increase of hippocampal extracellular 5-HT release. These findings indicate that 5-HT3 receptor blockade potentiates the antidepressant effects of SSRIs. Since both paroxetine and ondansetron are used clinically, it might be possible to validate this augmentation strategy in depressed patients.

The influence of 5-HTTLPR genotype on the association between the plasma concentration and therapeutic effect of paroxetine in patients with major depressive disorder.

IntroductionThe efficacy of treatment with selective serotonin reuptake inhibitors in patients with major depressive disorder (MDD) can differ depending on the patient's serotonin transporter-linked polymorphic region (5-HTTLPR) genotype, and the effects of varying plasma concentrations of drugs can also vary. We investigated the association between the paroxetine plasma concentration and clinical response in patients with different 5-HTTLPR genotypes.MethodsFifty-one patients were enrolled in this study. The Montgomery-Asberg Depression Rating Scale (MADRS) was used to evaluate patients at 0, 1, 2, 4, and 6 weeks. The patients' paroxetine plasma concentrations at week 6 were measured using high-performance liquid chromatography. Additionally, their 5-HTTLPR polymorphisms (alleles S and L) were analyzed using a polymerase chain reaction with specific primers. We divided the participants into two groups based on their L haplotype: the SS group and the SL and LL group. We performed single and multiple regression analyses to investigate the associations between MADRS improvement and paroxetine plasma concentrations or other covariates for each group.ResultsThere were no significant differences between the two groups with regard to demographic or clinical data. In the SS group, the paroxetine plasma concentration was significantly negatively correlated with improvement in MADRS at week 6. In the SL and LL group, the paroxetine plasma concentration was significantly positively correlated with improvement in MADRS at week 6 according to the results of the single regression analysis; however, it was not significantly correlated with improvement in MADRS at week 6 according to the results of the multiple regression analysis.ConclusionAmong patients with MDD who do not respond to paroxetine, a lower plasma concentration or a lower oral dose of paroxetine might be more effective in those with the SS genotype, and a higher plasma concentration might be more effective in those with the SL or LL genotype.

Higher anti-depressant dose and major adverse outcomes in moderate chronic kidney disease: a retrospective population-based study.

BackgroundMany older patients have chronic kidney disease (CKD), and a lower dose of anti-depressants paroxetine, mirtazapine and venlafaxine is recommended in patients with CKD to prevent drug accumulation from reduced elimination. Using information available in large population-based healthcare administrative databases, we conducted this study to determine if ignoring the recommendation and prescribing a higher versus lower dose of anti-depressants associates with a higher risk of adverse events.MethodsWe conducted a population-based cohort study to describe the 30-day risk of delirium in older adults who initiated a higher vs. lower dose of these three anti-depressants in routine care. We defined delirium using the best proxy available in our data sources - hospitalization with an urgent head computed tomography (CT) scan. We determined if CKD status modified the association between anti-depressant dose and outcome, and examined the secondary outcome of 30 day all-cause mortality. We used multivariable logistic regression analyses to estimate adjusted odds ratios (relative risk (RR)) and 95% confidence intervals.ResultsWe identified adults (mean age 75) in Ontario who started a new study anti-depressant at a higher dose (n = 36,651; 31%) or lower dose (n = 81,160; 69%). Initiating a higher vs. lower dose was not associated with an increased risk of hospitalization with head CT (1.09% vs. 1.27% (adjusted RR 0.90; 95% CI, 0.80 to 1.02), but was associated with a lower risk of all-cause mortality (0.76% vs. 0.97% RR 0.82; 95% CI, 0.71 to 0.95). Neither of these relative risks were modified by the presence of CKD (p = 0.16, 0.68, respectively).ConclusionsWe did not observe an increase in two adverse outcomes when study anti-depressants were initiated at a higher dose in elderly patients with moderate CKD. Contrary to our hypothesis, the 30-day risk of mortality was lower when a higher versus lower dose of anti-depressant was initiated in these patients, a finding which requires corroboration and further study.