Paroxetine effects

SSRIs are widely used for treatment of depression, as well as, for example, panic disorders and obsessive—compulsive disorder. These dmgs are well recognized as clinically effective antidepressants having an improved side-effect profile as compared to the TCAs and irreversible MAO inhibitors. Indeed, these dmgs lack the anticholinergic, cardiovascular, and sedative effects characteristic of TCAs. Their main adverse effects include nervousness /anxiety, nausea, diarrhea or constipation, insomnia, tremor, dizziness, headache, and sexual dysfunction. The most commonly prescribed SSRIs for depression are fluoxetine (31), fluvoxamine (32), sertraline (52), citalopram (53), and paroxetine (54). SSRIs together represent about one-fifth of total worldwide antidepressant unit sales. 

Risperidone (11) was also included among a a 1-adrenergic receptor antagonists to study a quantitative structure-activity relationship (99BMC2437). A pharmacophore model for atypical antipsychotics, including 11, was established (00MI41). An increased plasma level of 11 and 9-hydroxyrisperidone (12) was observed in combination with paroxetine (01 MI 13). The effect of vanlafaxine on the pharmacokinetics of 11 was reported (99MI13). 

Antidepressants are used in the treatment of neuropathic pain and headache. They include the classic tricyclic compounds and are divided into nonselective nor-adrenaline/5-HT reuptake inhibitors (e.g., amitriptyline, imipramine, clomipramine, venlafaxine), preferential noradrenaline reuptake inhibitors (e.g., desipramine, nortriptyline) and selective 5-HT reuptake inhibitors (e.g., citalopram, paroxetine, fluoxetine). The reuptake block leads to a stimulation of endogenous monoaminer-gic pain inhibition in the spinal cord and brain. In addition, tricyclics have NMDA receptor antagonist, endogenous opioid enhancing, Na+ channel blocking, and K+ channel opening effects which can suppress peripheral and central sensitization. Block of cardiac ion channels by tricyclics can lead to life-threatening arrhythmias. The selective 5-HT transporter inhibitors have a different side effect profile and are safer in cases of overdose [3]. 

Antidepressants Desipramine, imipramine, sertraline, fluoxetine, paroxetine, venlafaxine, bupropion, nefazodone, mirtazapine, gepirone, amineptine Mixed findings suggest that better designed studies may find a niche for some of these drugs. Amineptine was effective for withdrawal symptoms. 

Dr. Gibb s hypothesis regarding dopamine involvement, we thought that perhaps MBDB would not be neurotoxic because of a lack of effect on dopamine. But, in fact, it is neurotoxic as well, measured by whole-brain serotonin 5-HIAA and tritiated paroxetine binding sites. It is perhaps two-thirds the toxicity, on a molecular weight basis, of MDMA, but it is toxic. 

TABLE 2. Effects of repeated systemic administration of MDMA on the regional decreases in [ H]paroxetine-labeled serotonin uptake sites... 

In initial ICC studies, animals were treated with MDA or MDMA using the protocol described by Ricaurte et al. (1985). Adult Sprague-Dawley rats (150 to 200 g) reeeived subcutaneous injections of racemic MDA or MDMA every 12 hours for 4 days. Each dose was equivalent to 20 mg/kg of the free base. The rats were sacrificed by intracardiac aldehyde perfusion 2 weeks after the final dose. In order to study subacute effects for evidence of degeneration, additional rats received MDA every 12 hours for 2 days and were sacrificed 24 hours after the last injection. Additional experimental details are described elsewhere (O Heam et al. 1986 O Heam et al. 1988). A series of animals treated identically and in parallel were analyzed for changes in 5-HT levels and density of uptake sites using paroxetine binding (Yeh et al. 1986 Battaglia et al. 1987). 

Venlafaxine extended release, in doses of 75 to 225 mg/day, improves social anxiety, performance, and avoidance behavior with a reduction in disability.61 Treatment with venlafaxine results in response rates similar to those seen with paroxetine.60 Venlafaxine may be effective in SSRI non-responders.62 As with SSRIs, doses should be tapered slowly when discontinuing therapy. Tolerability is similar to that observed in depression trials with venlafaxine extended release. Common side effects are anorexia, dry mouth, nausea, insomnia, and sexual dysfunction. 

SSRIs are theorized to reduce the frequency of hot flashes by increasing serotonin in the central nervous system and by decreasing LH. Of the SSRIs, citalopram, paroxetine, and sertraline all have been studied and have demonstrated a reduction in hot flashes while treating other symptomatic complaints such as depression and anxiety.33 Venlafaxine, which blocks the reuptake of serotonin and norepinephrine, has demonstrated a reduction in hot flashes primarily in the oncology population.34 Overall, these antidepressant medications offer a reasonable option for women who are unwilling or cannot take hormonal therapies, particularly those who suffer from depression or anxiety. These agents should be prescribed at the lowest effective dose to treat symptoms and may be titrated based on individual response. 

Paroxetine-induced side effects were strongly associated with the HTR2A C/C genotype. Major depression Caucasian... 

Maj, J., Bijak, M., Dziedzicka-Wasylewska, M. etal. (1996). The effects of paroxetine given repeatedly on the 5-HT receptor subpopulations in the rat brain. Psychopharmacology, 127, 73-82. 

An open-label study of paroxetine and fluoxetine (Alonso et al, 1997) in depressed Hispanic (Mexican descent, n = 13) and non-Hispanic females (n = 13) showed no differences in response rates. At variance with the tricyclic data, Hispanic subjects complained of fewer side effects (2.2 2.0 vs. 5.1 2.5 p < 0.005), but twice as many terminated participation prior to study completion due to non-compliance, intolerable side effects or pregnancy. 

A prospective, randomized, placebo-controlled trial of paroxetine in adults with chronic post-traumatic stress disorder (PTSD) was recently conducted (Marshall etal., 2007). The subjects were New Yorkers, predominantly female (67%) and Hispanic (65.4%). Seventy subjects entered the study and after a one week placebo lead-in, 52 subjects were randomized to placebo or paroxetine for ten weeks. The subjects were treated with a flexible dosage design (mean dosage, 40.4 mg/day). Dropout rates were 32% for paroxetine and 51.9% for placebo. There were no differences in rates of adverse effects between treatment arms. Paroxetine was superior to placebo in ameliorating the primary symptoms of PTSD (56% vs. 22.2%). 

A pooled analysis of 14 875 adults (Hispanic, n = 361 White, n = 10 108 African American, n = 547 Asian, n = 112) who participated in 104 double-blind, placebo-controlled paroxetine trials for mood and anxiety disorders was performed to ascertain minority group differences (Roy-Byrne et al., 2005). There were significant differences in rates of response by ethnicity (p = 0.014) with the odds of responding being lower for the Asian and Hispanic subjects compared to the African American and White subjects. There was also a higher placebo response rate in Hispanic subjects. Rapidity of response and emergence of adverse effects were similar across groups. 

Gervasoni, D., Panconi, E., Henninot, V. et al. (2002). Effect of chronic treatment with milnacipran on sleep architecture in rats compared with paroxetine and imipramine. Pharmacol. Biochem. Behav. 73, 557-63. 

Smith, M. I., Piper, D. C., Duxon, M. S. Upton, N. (2002). Effect of SB-243213, a selective 5-HT2c receptor antagonist, on the rat sleep profile A comparison to paroxetine. Pharmacol. Biochem. Behav. 71, 599-605. 

It has been known for over 25 years that many of the tricyclic antidepressants (TCAs), e.g. imipramine and amitriptyline, are potent inhibitors of both norepinephrine and 5-HT reuptake. Some tricyclic antidepressants, e.g. desipramine, inhibit the uptake of norepinephrine much more potently than the uptake of 5-HT. Thus, it was unclear for some time whether the inhibition of 5-HT uptake played any role in the antidepressant action of those TCAs that possessed this pharmacological property. Recently, however, effective antidepressants such as fluoxetine, paroxetine and sertraline have been marketed and these SSRIs are much more potent inhibitors of the uptake of 5-HT than that of norepinephrine (Fig. 13-8). Thus, selective inhibition of the uptake of either norepinephrine or 5-HT can result in an antidepressant effect (Ch. 55). 

Treatment with a selective serotonin reuptake inhibitor is usually initiated in depressed patients with AD. Paroxetine causes more anticholinergic side effects than the other selective serotonin reuptake inhibitors. Ven-lafaxine may also be used. 

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