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PurposeRecent reviews have questioned the efficacy of selective serotonin reuptake inhibitors (SSRIs) above placebo response, and their working mechanisms remain unclear. New approaches to understanding the effects of SSRIs are necessary to enhance their efficacy. The aim of this study was to explore the possibilities of using cross-sectional network analysis to increase our understanding of symptom connectivity before and after SSRI treatment.MethodsIn two randomized controlled trials (total N = 178), we estimated Gaussian graphical models among 20 symptoms of the Beck Depression Inventory-II before and after 8 weeks of treatment with the SSRI paroxetine. Networks were compared on connectivity, community structure, predictability (proportion explained variance), and strength centrality (i.e., connectedness to other symptoms in the network).ResultsSymptom severity for all individual BDI-II symptoms significantly decreased over 8 weeks of SSRI treatment, whereas interconnectivity and predictability of the symptoms significantly increased. At baseline, three communities were detected; five communities were detected at week 8.ConclusionsFindings suggest the effects of SSRIs can be studied using the network approach. The increased connectivity, predictability, and communities at week 8 may be explained by the decrease in depressive symptoms rather than specific effects of SSRIs. Future studies with larger samples and placebo controls are needed to offer insight into the effects of SSRIs.Trial RegistrationThe trials described in this manuscript were funded by the NIMH.Pennsylvania/Vanderbilt study:5 R10 MH55877 (https://projectreporter.nih.gov/project_info_description.cfm?aid=6186633&icde=28344168&ddparam=&ddvalue=&ddsub=&cr=1&csb=default&cs=ASC&MMOpt=).Washington study:R01 MH55502 (https://projectreporter.nih.gov/project_info_description.cfm?aid=2034618&icde=28344217&ddparam=&ddvalue=&ddsub=&cr=5&csb=default&cs=ASC).

Purpose To investigate the effects of coadministration of paroxetine or fluvoxamine on the pharmacokinetics of aripiprazole in healthy adult Japanese with different CYP2D6 genotypes. Methods Fourteen CYP2D6 extensive metabolizer (EM) and 14 CYP2D6 intermediate metabolizer (IM) subjects were coadministered a single oral dose of aripiprazole 3 mg after steady-state plasma concentrations of the SSRIs paroxetine (20 mg/day) or fluvoxamine (100 mg/day) were reached by repeated oral doses for 6–7 days. The pharmacokinetics of aripiprazole with and without coadministration of SSRIs were compared according to CYP2D6 genotypes. Results Coadministration of paroxetine, a potent CYP2D6 inhibitor, decreased systemic clearance (CL/F) of aripiprazole by 58 and 23% in CYP2D6 EMs and IMs, respectively, demonstrating that the percentage inhibition of CYP2D6 activity by coadministration of paroxetine was apparently greater in CYP2D6 EMs than in IMs. Coadministration of fluvoxamine, a less potent CYP3A4 inhibitor, decreased the CL/F of aripiprazole by 39% in CYP2D6 EMs and 40% in IMs, indicating the same inhibitory effect on CYP enzymes, regardless of the CYP2D6 genotype. Percent contribution of CYP2D6 to total CL/F (CYP2D6 plus CYP3A4) of aripiprazole estimated as a reduced percentage of CL/F by CYP enzyme inhibition was 62% for CYP2D6 EMs and 24% for IMs in paroxetine coadministration, and 40% for CYP2D6 EMs and 18% for IMs in fluvoxamine coadministration. Conclusions There were marked differences in the degree of influence of paroxetine coadministration on the pharmacokinetics of aripiprazole between CYP2D6 EMs and IMs, but no apparent differences were found between two CYP2D6 genotypes in fluvoxamine coadministration. Aripiprazole can be used safely in combination with SSRIs that have a CYP enzyme-inhibitory action.

Purpose The main metabolic pathways of oxycodone, a potent opioid analgetic, are N-demethylation (CYP3A4) to inactive noroxycodone and O-demethylation (CYP2D6) to active oxymorphone. We performed a three-way, placebo-controlled, double-blind cross-over study to assess the pharmacokinetic and pharmacodynamic consequences of drug interactions with oxycodone. Methods The 12 participants (CYP2D6 extensive metabolizers) were pre-treated with placebo, ketoconazole or paroxetine before oral oxycodone ingestion (0.2 mg/kg). Results Pre-treatment with ketoconazole increased the AUC for oxycodone 2- to 3-fold compared with placebo or paroxetine. In combination with placebo, oxycodone induced the expected decrease in pupil diameter. This decrease was accentuated in the presence of ketoconazole, but blunted by paroxetine. In comparison to pre-treatment with placebo, ketoconazole increased nausea, drowsiness, and pruritus associated with oxycodone. In contrast, the effect of pre-treatment with paroxetine on the above-mentioned adverse events was not different from that of placebo. Ketoconazole increased the analgetic effect of oxycodone, whereas paroxetine was not different from placebo. Conclusions Inhibition of CYP3A4 by ketoconazole increases the exposure and some pharmacodynamic effects of oxycodone. Paroxetine pretreatment inhibits CYP2D6 without inducing relevant changes in oxycodone exposure, and partially blunts the pharmacodynamic effects of oxycodone due to intrinsic pharmacological activities. Pharmacodynamic changes associated with CYP3A4 inhibition may be clinically important in patients treated with oxycodone.

This study was aimed at resolving the time course of clinical action of antidepressants (ADs) and the type of early behavioral changes that precede recovery in treatment-responsive depressed patients. The first goal was to identify, during the first 2 weeks of treatment, the onset of clinical actions of the selective serotonin reuptake inhibitor (SSRI), paroxetine, and the selective noradrenergic reuptake inhibitor, desipramine (DMI). The second aim was to test the hypothesis that the two pharmacologic subtypes would induce different early behavioral changes in treatment-responsive patients. The design was a randomized, parallel group, placebo-controlled, double-blind study for 6 weeks of treatment following a 1-week washout period. The study utilized measures of the major behavioral components of the depressive disorder as well as overall severity. The results indicated that the onset of clinical actions of DMI ranged from 3 to 13 days, averaged 13 days for paroxetine, and was 16–42 days for placebo. Furthermore, as hypothesized, the different types of ADs initially impacted different behavioral aspects of the disorder. After 1 week of treatment, DMI produced greater reductions in motor retardation and depressed mood than did paroxetine and placebo, and this difference persisted at the second week of treatment. Early improvement in depressed mood–motor retardation differentiated patients who responded to DMI after 6 weeks of treatment from those that did not. Paroxetine initially reduced anxiety more in responders than in nonresponders, and by the second week, significantly improved depressed mood and distressed expression in responders to a greater extent. Depressed patients who responded to placebo showed no consistent early pattern of behavior improvement. Early drug-specific behavioral changes were highly predictive of ultimate clinical response to the different ADs, results that could eventually be applied directly to clinical practice.

Rationale Two biomarkers: concentration ratio of O -desmethylvenlafaxine/venlafaxine and concentration sum of venlafaxine +  O -desmethylvenlafaxine were adopted to indicate venlafaxine responses, but neither is validated. Objectives To evaluate the ability of two biomarkers in reflecting venlafaxine pharmacokinetic variations, and to further examine their relationship with venlafaxine treatment outcomes. Methods Two well-defined influencing factors: CYP2D6 genotypes and drug interactions were enriched into a three-period crossover study to produce venlafaxine pharmacokinetic variations: In each period, healthy CYP2D6 extensive metabolizers (EM group; n  = 12) and CYP2D6*10/*10 intermediate metabolizers (IM group; n  = 12) were pretreated with clarithromycin (CYP3A4 inhibitor), or nothing (control), or clarithromycin + paroxetine (CYP3A4 + CYP2D6 inhibitors), before administration of a single-dose of 75 mg venlafaxine. Both biomarkers were evaluated (1) for their relationship with the influencing factors in healthy volunteers and (2) for their relationships with the venlafaxine responses/adverse events reported in two patient studies. Results Significant venlafaxine pharmacokinetic variations were observed between the EM and IM groups (geometric mean ratio [95 % CI] of area under the curve, 3.0 [1.8–5.1] in the control period), and between the control and clarithromycin + paroxetine periods (4.1 [3.5–4.7] and 2.0 [1.7–2.4] in the EM and IM group, respectively). O -Desmethylvenlafaxine/venlafaxine was superior to venlafaxine +  O -desmethylvenlafaxine to reflect the influencing factors. In the patient studies, O -desmethylvenlafaxine/venlafaxine > 4 showed high precision in predicting venlafaxine responders/partial-responders (92 %) and patients without venlafaxine-related adverse events (88 %); the O -desmethylvenlafaxine/venlafaxine < 4 and venlafaxine +  O -desmethylvenlafaxine > 400 ng/ml combination showed higher precision (100 %) than O -desmethylvenlafaxine/venlafaxine < 4 alone (65 %) in predicting venlafaxine non-responders. Conclusion We propose using O -desmethylvenlafaxine/venlafaxine for CYP2D6 phenotyping, and O -desmethylvenlafaxine/venlafaxine with venlafaxine +  O -desmethylvenlafaxine for predicting venlafaxine treatment outcomes in future prospective studies.

Rationale After exposure to a severe traumatic event, avoidance, fear sensitization, and increased anxiety are among features that can persist over time in people developing posttraumatic stress disorder (PTSD). Basic research on treatment interfering with these symptoms can provide insights to improve PTSD treatment. Objectives The purposes of the present study were to induce these behavioral changes in mice and examine whether paroxetine would interfere with their expression. Methods Mice were submitted to avoidance training with a low (0.4 mA) or high (1.5 mA) foot-shock intensity, as mild and severe stressors, respectively, and posttraining avoidance was evaluated 1 and 12 days later. Fear sensitization, measured as increased freezing to a neutral tone, and enhanced contextual fear, measured as increased freezing to a conditioned context (wherein all mice received a 0.4-mA foot-shock), were assessed during this time window. An elevated plus maze test was also used to assess mouse anxiety-like behavior. Results Persistent avoidance, persistent fear sensitization, and long-term enhancement of contextual fear and increased anxiety-like behavior were established only in mice that received the 1.5-mA foot-shock during avoidance training. Paroxetine (at 8 mg/kg/day), injected from day 5 to day 11 after avoidance training, suppressed all of these behavioral changes. Conclusions These data provide additional evidence for the role of paroxetine against expression of PTSD-like behaviors in mice.

Background The drug treatments of choice for obsessive-compulsive disorder (OCD) are serotonin reuptake inhibitors (SRIs). However, a correlation between the neuropeptide oxytocin in cerebrospinal fluid and the severity of OCD has previously been shown, and oxytocin and serotonin are interconnected within the brain. Few studies have investigated whether SRIs have any effect on oxytocin; thus, our aim was to explore the possibility that oxytocinergic mechanisms contribute to the anti-obsessive effect of SRIs. Method In a randomized, double-blind trial, comparing SRIs (clomipramine and paroxetine) with placebo in 36 adults with OCD (characterized for subtypes), plasma oxytocin was measured with radioimmunoassay after plasma extraction, at baseline, after 1 week, and after 4 weeks of treatment, and related to baseline severity and clinical response after 12 weeks, as measured by the Yale-Brown Obsessive Compulsive Scale (Y-BOCS). Results Baseline oxytocin levels correlated positively with baseline Y-BOCS ratings, but only among the future SRI responders. Patients with early onset of OCD had higher baseline oxytocin. During treatment, plasma oxytocin did not differ between SRI and placebo treatment. In SRI responders, plasma oxytocin first decreased and then increased; in non-responders (to SRI as well as to placebo), the reverse was the case. After 4 weeks, treatment responders had attained higher oxytocin levels compared to non-responders. The intra-individual range (i.e. the variability) of plasma oxytocin between measurements was the measure that best differentiated responders from non-responders. This range was higher in responders than non-responders, and lower in patients with autistic traits. Conclusions SRIs have highly variable effects on plasma oxytocin between individuals. The associations between baseline oxytocin and OCD severity and between oxytocin changes and treatment response support the notions that oxytocin is involved in OCD pathophysiology, and that the anti-obsessive effects of SRIs are partly exerted through oxytocinergic mechanisms.

A 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. In 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. Hydrocodone 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. In 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.

We tested the theory that central serotonin (5-hydroxytryptamine 9 or 5-HT) activity regulates aggression by modulating response to provocation. Eighty men and women (40 with and 40 without a history of aggression) were randomly assigned to receive either 40 mg of paroxetine (to acutely augment serotonergic activity) or a pfaebo, administered using double-blind procedures. Aggression was assessed during a competitive reaction time game with a fictitious opponent. Shocks were selected by the participant and opponent before each trial, with the hser on each trial receiving the shock set by the other player. Provocation was manipulated by having the opponent select increasingly intense shocks for the participant and eventually an ostensibly severe shock toward the end of the trials. Aggression was measured by the number of severe shocks set by the participant for the opponent. As predicted, aggressive responding after provocation was attenuated by augmentation of serotonin in individuals with a pronounced history of aggression.

Due to the physiological coupling with metabolism, brain perfusion is a potential aid in understanding the effects of medication on neural activity in vivo. In this study, arterial spin labeling (ASL) was used to quantify the effect of seven days of administration of paroxetine (20mg), bupropion (150mg) on cerebral blood flow levels at rest in a double-blind, placebo-controlled crossover design in N=21 healthy participants. Paroxetine administration was associated with diffuse cortical perfusion decrements, more marked in the prefrontal region, and with decrements in the striatum, caudate and the basal forebrain. The effect of bupropion on the cortex was similar but less conspicuous. In the brainstem, there was suggestive evidence of perfusion decrements in the main serotonergic and noradrenergic nuclei. These results demonstrate the existence of effects on rest perfusion of antidepressant medication of potential use in monitoring its action. The observed perfusion reductions may be related to compensatory decrements of monoaminergic neural activity in the initial phases of treatment that are observed under both drugs following the increase in extracellular concentration of transmitters.