Influence of the selective serotonin re-uptake inhibitor, paroxetine, on gastric sensorimotor function in humans.
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BACKGROUND: The role of 5-hydroxytryptamine in the control of gastric fundus tone in humans is still unknown. Selective 5-hydroxytryptamine re-uptake inhibitors act both centrally and peripherally to enhance the availability of physiologically released 5-hydroxytryptamine. AIM: To study the influence of a selective 5-hydroxytryptamine re-uptake inhibitor, paroxetine, on gastric fundus tone, on the perception to gastric distension and on gastric accommodation to a meal. METHODS: Sixteen healthy volunteers underwent a gastric barostat study on two occasions, after pre-treatment with placebo or paroxetine, 20 mg/day. Graded isobaric and isovolumetric distensions were performed and perception was scored by a questionnaire. Subsequently, the amplitude of the gastric accommodation to a mixed liquid meal was also measured. RESULTS: Pre-treatment with paroxetine did not alter the thresholds for perception and discomfort during isobaric (4.7 +/- 2.3 vs. 4.0 +/- 2.0 mmHg and 13.3 +/- 3.1 vs. 12.7 +/- 2.3 mmHg above the minimum intragastric distending pressure, N.S.) and isovolumetric (307 +/- 90 vs. 417 +/- 114 mL and 772 +/- 74 vs. 750 +/- 76 mL, N.S.) distensions. Paroxetine significantly enhanced the amplitude of the meal-induced fundus relaxation (136 +/- 51 vs. 255 +/- 43 mL, P < 0.05). CONCLUSIONS: Pre-treatment with paroxetine enhances gastric accommodation to a meal. These data suggest that the release of 5-hydroxytryptamine, probably at the level of the enteric nervous system, is involved in the control of the accommodation reflex in humans, and that paroxetine may be beneficial to patients with impaired post-prandial fundus relaxation. (+info)
Simple method of paroxetine determination using a single channel FIA with no in-line reaction process.
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A flow-injection analysis (FIA) of paroxetine hydrochloride (PRX), a selective serotonin reuptake inhibitor (SSRI) currently used as an antidepressant drug, is described. A 0.1 mol dm(-3) acetate buffer at pH 3.07 was found to be thebest solvent. The analyte was detected at 293 nm. The calibration equation was linear over the range of 1.07 x 10(-6) to 5.35 x 10(-6) mol dm(-3). The limit of detection (LOD) and the limit of quantitation (LOQ) were 3.2 x 10(-7) and 9.5 x 10(-7) mol dm(-3), respectively. The proposed method was applied to the determination of PRX in pharmaceutical preparations. The results were compared with those obtained by a conventional batchwise UV-spectrophotometry. (+info)
Quality of life and metabolic status in mildly depressed women with type 2 diabetes treated with paroxetine: a single-blind randomised placebo controlled trial.
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BACKGROUND: Depression is prevalent in people with type 2 diabetes and affects both glycemic control and overall quality of life. The aim of this trial was to evaluate the effect of the antidepressant paroxetine on metabolic control, quality of life and mental well-being in mildly depressed women with type 2 diabetes. METHODS: We randomised 15 mildly depressed women with non-optimally controlled type 2 diabetes to a 10-week single-blind treatment with either paroxetine 20 mg per day or placebo. Primary efficacy measurements were glycemic control and quality of life. Glycosylated hemoglobin A1c (GHbA1c) was used as a measure of glycemic control. Quality of life was evaluated using RAND-36. Mental state was assessed using two clinician-rated scoring instruments, Hamilton's Anxiety Scale (HAM-A) and Montgomery-Asberg's Depression Rating Scale (MADRS), and a patient-rated scoring instrument, Beck's Depression Inventory (BDI). RESULTS: At the end of the study no significant difference between groups in improvement of quality of life was found. A trend towards a superior improvement in glycemic control was found in the paroxetine group (p = 0.08). A superior increase in sex-hormone-binding-globuline (SHBG) levels was evidenced in the paroxetine group (p = 0.01) as a sign of improved insulin sensitivity. There was also a trend for superior efficacy of paroxetine in investigator-rated anxiety and depression. This notion was supported by a trend for superior decrease of serum cortisol levels in the paroxetine group (p = 0.06). CONCLUSION: Paroxetine has a beneficial effect on measures of insulin sensitivity and may improve glycemic control. Larger studies of longer duration are needed to verify the benefits of paroxetine in type 2 diabetes. While waiting for more conclusive evidence it seems sensible to augment standard care of type 2 diabetes with paroxetine even in patients who do not fulfil routine psychiatric criteria for initiation of antidepressant drug treatment. (+info)
Involvement of CYP3A4, CYP2C8, and CYP2D6 in the metabolism of (R)- and (S)-methadone in vitro.
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To clarify the oxidative metabolism of methadone (R)- and (S)-enantiomers, the depletion of parent (R)- and (S)-methadone and the formation of racemic 2-ethylidene-1,5-dimethyl-3,3-diphe-nylpyrolidine were studied using human liver microsomes and recombinant cytochrome P450 enzymes. Based on studies with isoform-selective chemical inhibitors and expressed enzymes, CYP3A4 was the predominant enzyme involved in the metabolism of (R)-methadone. However, it has different stereoselectivity toward (R)- and (S)-methadone. In recombinant CYP3A4, the metabolic clearance of (R)-methadone was about 4-fold higher than that of (S)-methadone. CYP2C8 is also involved in the metabolism of methadone, but its contribution to the metabolism of (R)-methadone was smaller than that of CYP3A4. But for the metabolism of (S)-methadone, the roles of CYP2C8 and CYP3A4 appeared equal. Although CYP2D6 is involved in the metabolism of (R)- and (S)-methadone, its role was smaller compared with CYP3A4 and CYP2C8. Using clinically relevant concentrations of ketoconazole (1 microM, selective CYP3A4 inhibitor), trimethoprim (100 microM, selective CYP2C8 inhibitor), and paroxetine (5 microM, potent CYP2D6 inhibitor), these inhibitors decreased the hepatic metabolism of (R)-[(S)-]methadone by 69% (47%), 22% (51%), and 41% (77%), respectively. However, inhibition of the metabolism of (R)- and (S)-methadone by paroxetine was due to inhibition not only of CYP2D6, but also CYP3A4 and, to a minor extent, CYP2C8. The present in vitro findings indicated that CYP3A4, CYP2C8, and CYP2D6 are all involved in the stereoselective metabolism of methadone (R)- and (S)-enantiomers. These data suggest that coadministration of inhibitors of CYP3A4 and CYP2C8 may produce clinically significant drug-drug interactions with methadone. (+info)
Regulatory effects of reboxetine treatment alone, or following paroxetine treatment, on brain noradrenergic and serotonergic systems.
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When patients do not respond to an initial antidepressant, one clinical approach is to switch to an agent in a different pharmacological class. However, few studies have examined the neurochemical consequences of this practice. To study this, we examined changes in binding sites in rat brain for norepinephrine (NET) and serotonin transporters (SERT), alpha1, alpha2, and beta1 adrenergic receptors after chronic administration of paroxetine (PRX), reboxetine (RBX), or PRX followed by RBX. We also examined the effects of these treatments on mRNA expression for tyrosine hydroxylase (TH). RBX treatment for 3 weeks reduced NET binding significantly, by approximately 40% in terminal field areas, and 6 weeks of RBX reduced it even more, by approximately 60%. RBX treatment for 3 and 6 weeks reduced beta1 adrenergic receptor-binding sites equally, by 50-60%. At no time did RBX treatment reduce SERT-binding sites. PRX treatment had no effect on beta1 adrenergic or NET-binding sites, but reduced SERT-binding sites by 75-80%. Neither treatment altered mRNA for TH, alpha1, or alpha2 adrenergic receptor-binding sites. When 3 weeks of RBX treatment followed 3 weeks of PRX treatment, NET-binding sites were reduced to the same extent as measured after 6 weeks of RBX treatment alone, indicating that PRX pretreatment may have 'primed' the subsequent regulatory effect of RBX on the NET. Thus, pretreatment of rats with PRX actually enhanced at least one regulatory effect of RBX treatment on the noradrenergic system, and did not interfere with any other pharmacological effect caused by RBX treatment. (+info)
Effects of combined administration of 5-HT1A and/or 5-HT1B receptor antagonists and paroxetine or fluoxetine in the forced swimming test in rats.
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Clinical data suggest that coadministration of pindolol, a 5-HT1A/5-HT1B/beta-adrenoceptor antagonist, and selective serotonin reuptake inhibitors (SSRIs) may shorten the time of onset of a clinical action and may increase beneficial effects of the therapy of drug-resistant depression. Effects of combined administration of SSRIs and 5-HT receptor ligands are currently evaluated in animal models for the detection of an antidepressant-like activity; however, the obtained results turned out to be inconsistent. The aim of the present study was to investigate effects of a 5-HT1A antagonist (WAY 100635), 5-HT1B antagonists (SB 216641 and GR 127935) or pindolol, given in combination with paroxetine or fluoxetine (SSRIs), in the forced swimming test in rats (Porsolt test). When given alone, paroxetine (10 and 20 mg/kg), fluoxetine (10 and 20 mg/kg), WAY 100635 (0.1 and 1 mg/kg), SB 216641 (2 mg/kg), GR 127935 (10 and 20 mg/kg) and pindolol (4 and 8 mg/kg) did not shorten the immobility time of rats in that test. Interestingly, SB 216641 administered alone at a dose of 4 mg/kg produced a significant reduction of the immobility time in that test. A combination of paroxetine (20 mg/kg) and WAY 100635 or pindolol failed to reveal a significant interaction; on the other hand, when paroxetine was given jointly with SB 216641 (2 mg/kg) or GR 127935 (10 and 20 mg/kg), that combination showed a significant antiimmobility action in the forced swimming test in rats. The active behaviors in that test did not reflect increased general activity because combined administration of both the 5-HT1B antagonists and paroxetine failed to alter the locomotor activity of rats, measured in the open field test. Coadministration of fluoxetine and all the antagonists used did not affect the behavior of rats in the forced swimming test. The obtained results seem to indicate that blockade of 5-HT1B receptors, but not 5-HT1A ones, can facilitate the antidepressant-like effect of paroxetine in the forced swimming test in rats. No interaction was observed between fluoxetine and 5-HT1A/5-HT1B receptor antagonists. (+info)
Effect of combined treatment with paroxetine and transcranial magnetic stimulation (TMS) on the mitogen-induced proliferative response of rat lymphocytes.
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Depression is associated with abnormal functions of the immune system. In this study, we investigated how two modem antidepressant therapies, chronic treatment with transcranial magnetic stimulation (TMS) and administration of an antidepressant belonging to selective serotonin reuptake inhibitors (SSRI), paroxetine, affect the proliferative response of thymocytes and splenocytes stimulated in vitro with various mitogens. Paroxetine (10 mg/kg) and TMS (B = 1.2 T, f = 30 Hz, t = 330 s) were applied once daily for 12 consecutive days, while, if given jointly paroxetine was injected 30 min before TMS. The mitogens used were: concanavalin A (Con A), pokeweed mitogen (PWM) or lipopolysaccharide (LPS). While either treatment applied alone had no effect on proliferative response, the joint application of paroxetine and TMS significantly depressed it. The literature data suggest that pulsed magnetic field may directly inhibit mitogen-activated lymphocyte proliferation, which is also inhibited by the presence of high level of serotonin. The present results suggest that both effects are additive, and because of that application of both treatments, whose effects alone are insufficient to prompt the reaction, possibly because adaptive changes during chronic treatment, results in a significant inhibition of lymphocyte proliferation. (+info)
Paroxetine-induced conversion of cytochrome P450 2D6 phenotype and occurence of adverse effects.
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The paper is focused on a comparison of the distribution of side effects of treatment with paroxetine within a group of 30 patients genotyped and phenotyped for their CYP 2D6 metabolic status. Genotyping procedure showed that the patient group did not include any individual with poor metabolizer (PM) genotype; on the other hand, most patients (24) were classified as PMs by virtue of their phenotype, which suggests that a conversion to the poor metabolic phenotype ("phenocopy") occurred, probably as a consequence of a long-term administration of the strong CYP 2D6 inhibitor paroxetine. As to the occurence of common adverse effects, no marked difference between subjects converted into the PM group and those who had no history of such conversion was found. A significantly higher incidence of sexual dysfunction (p < 0.05) was, nevertheless, recorded in patients with the PM phenotype. The results of the study may provide evidence that it is the metabolic phenotype status, rather than the genetically given enzyme capacity (CYP 2D6 genotype), that is relevant for the actual toleration of treatment with CYP 2D6 inhibitors. (+info)