In the present study, we investigated the relationship between the serotonin transporter gene linked polymorphic regions (5-HTTLPR) or plasma paroxetine levels and clinical response to paroxetine in depressed patients. Sixty patients who met the DSM-IV criteria for major depressive disorder were enrolled in the study. Twenty-two were male and 38 were female, with ages ranging from 25 to 71 (mean +/- SD = 42 +/- 16) years. The clinical improvement of patients was assessed using the Hamilton rating scale for depression (Ham-D) before and every week after paroxetine administration. According to the data reported previously, patients with an at least 50% decrease in their Ham-D score were classified as responders. The results showed that the plasma paroxetine levels at 4 weeks were significantly higher in responders (rapid responders) than in nonresponders. On the other hand, no significant associations were found between the L genotype (L/L, L/S) or S genotype (S/S) and the response rates either at 4 weeks or 8 weeks. These results suggest that patients with higher plasma levels at 4 weeks might respond rapidly to paroxetine treatment, but the final response rate at 8 weeks will be independent of the plasma paroxetine levels and the 5-HTTLPR L/S genotype.
2009 John Wiley & Sons, Ltd.