Whole-Blood Serotonin during Clomipramine Treatment of Juvenile Obsessive—Compulsive Disorder

Whole-blood serotonin (5-HT) concentration was assessed in 15 children and adolescents with obsessive–compulsive disorder (OCD) before and during treatment with clomipramine (CMI). Pretreatment blood 5-HT content had no correlation with clinical improvement during drug therapy. CMI administration produced a marked reduction in blood 5-HT content during the first 4 weeks of treatment, but not during the second 4 weeks of treatment. Significant clinical improvement occurred, however, during both 4-week periods of treatment. The percentage of change in blood 5-HT concentrations during the first 4 weeks of CMI administration had a significant positive correlation with the percentage of clinical change reached after 8 weeks of treatment. In contrast, CMI dosage was negatively correlated with the declines in symptom severity and blood 5-HT content. The results provide further evidence that the inhibition of 5-HT uptake by CMI is associated with its amelioration of OCD. The temporal delay between 5-HT uptake inhibition and clinical improvement suggests that biochemical adaptations to the pharmacological actions of CMI, rather than the direct drug effects themselves, are associated with clinical improvement.