The mechanism of action of sertraline is presumed to be linked to its ability to inhibit the neuronal reuptake of serotonin. It has only very weak effects on norepinephrine and dopamine neuronal reuptake. At clinical doses, sertraline blocks the uptake of serotonin into human platelets.
Like most clinically effective antidepressants, sertraline downregulates brain norepinephrine and serotonin receptors in animals. In receptor binding studies, sertraline has no significant affinity for adrenergic (alpha1, alpha2 & beta), cholinergic, GABA, dopaminergic, histaminergic, serotonergic (5-HT1A, 5-HT1B, 5-HT2) or benzodiazepine binding sites.
In placebo-controlled studies in normal volunteers, ZOLOFT (sertraline hydrochloride) did not cause sedation and did not interfere with psychomotor performance.
Pharmacokinetics: Following multiple oral once-daily doses of 200 mg, the mean peak plasma concentration (Cmax) of sertraline is 0.19 µg/mL occurring between 6 to 8 hours post-dose. The area under the plasma concentration time curve is 2.8 mg hr/l. For desmethylsertraline, Cmax is 0.14 µg/mL, the half-life 65 hours and the area under the curve 2.3 mg hr/l. Following single or multiple oral once-daily doses of 50 to 400 mg/day the average terminal elimination half-life is approximately 26 hours. Linear dose proportionality has been demonstrated over the clinical dose range of 50 to 200 mg/day.
Food appears to increase the bioavailability by about 40%: it is recommended that ZOLOFT be administered with meals.
Sertraline is extensively metabolized to N-desmethylsertraline, which shows negligible pharmacological activity. Both sertraline and N-desmethylsertraline undergo oxidative deamination and subsequent reduction, hydroxylation and glucuronide conjugation. Biliary excretion of metabolites is significant.
Approximately 98% of sertraline is plasma protein bound. The interactions between sertraline and other highly protein bound drugs have not been fully evaluated - see PRECAUTIONS section.
The pharmacokinetics of sertraline itself appears to be similar in young and elderly subjects. Plasma levels of N-desmethylsertraline show a 3-fold elevation in the elderly following multiple dosing, however, the clinical significance of this observation is not known.
Analyses for gender effects on outcome did not suggest any differential responsiveness on the basis of sex.
Liver and Renal Disease: The pharmacokinetics of sertraline in patients with significant hepatic or renal dysfunction have not been determined - see PRECAUTIONS and DOSAGE AND ADMINISTRATION.
Panic Disorder: Four placebo-controlled clinical trials have been performed to investigate the efficacy of ZOLOFT in panic disorder: two flexible dose studies and two fixed dose studies. At the last week of treatment (week 10 or 12), both flexible dose studies and one of the fixed dose studies showed statistically significant differences from placebo in favour of ZOLOFT in terms of mean change from baseline in the total number of full panic attacks (last observation carried forward analysis). As the flexible dose studies were of identical protocol, data for these investigations can be pooled. The mean number of full panic attacks at baseline was 6.2/week (N=167) in the ZOLOFT group and 5.4/week in the placebo group (N=175). At week 10 (last observation carried forward analysis), the mean changes from baseline were -4.9/week and -2.5/week for the ZOLOFT and placebo groups, respectively. The proportion of patients having no panic attacks at the final evaluation was 57% in the placebo group and 69% in the ZOLOFT group. The mean daily dose administered at the last week of treatment was approximately 120 mg (range: 25-200 mg) in the flexible dose studies. No clear dose-dependency has been demonstrated over the 50 to 200 mg/day dose range investigated in the fixed dose studies.
Obsessive-Compulsive Disorder: Five placebo-controlled clinical trials, in adults, of 8 to 16 weeks in duration have been performed to investigate the efficacy of ZOLOFT in obsessive-compulsive disorder: four flexible dose studies (50-200 mg/day) and one fixed dose study (50, 100, & 200 mg/day). Results for three of the four flexible dose studies and the 50 and 200 mg dose groups of the fixed dose study were supportive of differences from placebo in favour of ZOLOFT in terms of mean change from baseline to endpoint on the Yale-Brown Obsessive-Compulsive Scale and/or the National Institute of Mental Health Obsessive-Compulsive Scale (last observation carried forward analysis). No clear dose-dependency was demonstrated over the 50 to 200 mg/day dose range investigated in the fixed dose studies. In the flexible dose studies, the mean daily dose administered at the last week of treatment ranged from 124-180 mg.