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Paroxetine (Paxil)

paxilPaxil is available by prescription in the United States.

Addictive Potential: Low more…

Emergency Room Visits Yearly: Unknown

Mandatory Minumum Sentence: Not Scheduled, Does Not Apply; Legal by Prescription

Mechanism of Action: Increases the Neurotransmitter Serotonin

Overview:

Paroxetine or paroxetine hydrochloride is a selective serotonin reuptake inhibitor (SSRI) antidepressant. It was released in 1992 by the pharmaceutical company GlaxoSmithKline and has since become one of the most prescribed antidepressants on the market due to its apparent efficacy in treating depression as well as a spectrum of anxiety disorders ranging from panic attacks to phobias.

Side Effects and Adverse Reactions:

Among the common adverse effects associated with paroxetine treatment of depression and listed in the prescribing information, those with the greatest difference from placebo are nausea (26% on paroxetine vs 9% on placebo), somnolence (23% vs. 9% on placebo), ejaculatory disturbance (13% vs. 0% on placebo), other male genital disorders (10% vs. 0% on placebo), asthenia (15% vs. 6% on placebo), sweating (11% vs. 2% on placebo), dizziness (13% vs. 6% on placebo), insomnia (13% vs. 6% on placebo), dry mouth (18% vs. 12% on placebo), constipation (14% vs. 9% on placebo), and tremor (8% vs. 2% on placebo). Other side effects include headache, agitation, weight gain, impaired memory and paresthesia.

General side effects are mostly present during the first 1–4 weeks while the body acquires a tolerance to the drug, although once this happens, withdrawal can cause a rebound effect with symptoms re-emerging in an exaggerated form for very long periods of time. Almost all SSRIs are known to cause either one or more of these symptoms. A person receiving paroxetine treatment may experience a few, all, or none of the listed side-effects, and most side-effects will disappear or lessen with continued treatment, though some may last throughout the duration. Side effects are also often dose-dependent, with fewer and/or less severe symptoms being reported at lower dosages, and/or more severe symptoms being reported at higher dosages. Increases or changes in dosage may also cause symptoms to reappear or worsen.

On 9 December 2004, the European Medicines Agency’s (EMEA) Committee for Medicinal Products for Human Use (CHMP) informed patients, prescribers, and parents that paroxetine should not be prescribed to children. CHMP also gave a warning to prescribers recommending close monitoring of adult patients at high risk of suicidal behaviour and/or suicidal thoughts. CHMP does not prohibit use of paroxetine with high risk adults but urges extreme caution. Due to reports of adverse withdrawal reactions upon terminating treatment, CHMP recommends to reduce gradually over several weeks or months if the decision to withdraw is made.

A statistical analysis of paroxetine clinical trials in children and adolescents was conducted by the FDA in 2004. It indicated a statistically significant 2.7-fold raise in suicide behavior and ideation as compared to placebo. The trend for increased suicidality was observed in both trials for depression and for anxiety disorders.

Cases of akathisia and activation syndrome have been observed during paroxetine treatment.

Rarely serotonin syndrome, a severe adverse effect may occur.

Paroxetine and other SSRIs have been shown to cause sexual side effects in most patients, both males and females. In males, paroxetine is also linked to sperm DNA fragmentation.

Mania or hypomania may occur as a serious side effect of paroxetine, affecting up to 8% of psychiatric patients treated. This side effect can occur in individuals with no history of mania but it is more likely to occur in those with bipolar or with a family history of mania.

Schmitt et al. (2001) suggested that paroxetine negatively affects memory (i.e., IQ). In their study, healthy participants given paroxetine for 14 days (20 mg for days 1–7 and 40 mg days 8–14) showed poorer recall of words on day 14 compared to those receiving a placebo. Schmitt et al. did not take into account a significant difference in verbal recall at baseline between the paroxetine and placebo groups, however, and this difference may have been the source of the significant group difference on day 14. Moreover, participants receiving paroxetine recalled as many words at baseline as they recalled on day 14, which is not consistent with the conclusion that paroxetine negatively affects verbal recall.

SSRI discontinuation syndrome

Many psychoactive medications can cause withdrawal symptoms upon discontinuation from administration. Evidence has shown that paroxetine has among the highest incidence rates and severity of withdrawal syndrome of any medication of its class. Common withdrawal symptoms for paroxetine include nausea, dizziness, lightheadedness and vertigo; insomnia, nightmares and vivid dreams; feelings of electricity in the body, as well as crying and anxiety. Liquid formulation of paroxetine is available and allows a very gradual decrease of the dose, which may prevent discontinuation syndrome. Another recommendation is to temporarily switch to fluoxetine, which has a longer half-life and thus decreases the severity of discontinuation syndrome.

In addition, The Lancet published an analysis of World Health Organization data showing SSRIs taken during pregnancy may cause withdrawal symptoms, including convulsions, in newborn children: among “93 suspected cases of SSRI-induced neonatal withdrawal syndrome…64 were associated with paroxetine, 14 with fluoxetine, nine with sertraline, and seven with citalopram.”

Paroxetine and pregnancy

The American College of Obstetricians and Gynecologists recommends that pregnant women and women planning to become pregnant should avoid using paroxetine. According to the prescribing information “epidemiological studies have shown that infants born to women who had first trimester paroxetine exposure had an increased risk of cardiovascular malformations, primarily ventricular and atrial septal defects (VSDs and ASDs). In general, septal defects range from those that are symptomatic and may require surgery to those that are asymptomatic and may resolve spontaneously. If a patient becomes pregnant while taking paroxetine, she should be advised of the potential harm to the fetus. Unless the benefits of paroxetine to the mother justify continuing treatment, consideration should be given to either discontinuing paroxetine therapy or switching to another antidepressant. For women who intend to become pregnant or are in their first trimester of pregnancy, paroxetine should only be initiated after consideration of the other available treatment options.” These conclusions are supported by multiple systematic reviews and meta-analyses that found that, on average, the use of paroxetine during pregnancy is associated with about 1.5-1.7-fold increase in congenital birth defects, in particular, heart defects. A recent non-systematic review in the Journal of Clinical Psychiatry, with the lead author, Salvatore Gentile, reporting to have received material or financial support from GSK, came to a different conclusion: “the teratogenic potential of paroxetine that has been reported in some studies remains unproven.” Gentile called for large, epidemiologic, prospective, controlled studies on “mothers who accept taking paroxetine during pregnancy”. Other reviews vary on whether the teratogenic risks outweigh the risk of disease relapse if the drug is discontinued: some advocate discontinuation, while others suggest caution; even where the overview of antidepressants generally is favorable, paroxetine is singled out for specific risks.

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