Prolactin response to dl-fenfluramine challenge before and after treatmentwith paroxetine

The prolactin response to dl-fenfluramine (an indirect central serotonin ag onist) challenge has been used to assess serotonergic function and appears to be blunted in depressed patients. We used this method to determine wheth er the serotonergic deficit in depressed patients is corrected by treatment with paroxetine. Prior to treatment with paroxetine sixteen depressed pati ents received a placebo challenge followed by a dl-fenfluramine challenge t he next day. The same two challenges were repeated after treatment. Prolact in baseline levels were measured before pill administration, and then hourl y for 5 hours. Fenfluramine/ norfenfluramine levels were assayed at each ti me point after drug administration. Treatment with paroxetine significantly increased the baseline prolactin level independently of treatment response but positively correlated with paroxetine dose. We found that pre-treatmen t prolactin response to dl-fenfluramine challenge did not predict clinical response to paroxetine, nor did the prolactin response change significantly after treatment. There was no significant difference in the post-treatment prolactin response between treatment responders and treatment non-responde rs. We found evidence of increased prolactin levels that may reflect effect s of paroxetine in enhancing serotonin levels. Acute release of serotonin a s measured by the prolactin response to fenfluramine is not altered by paro xetine treatment. (C) 2001 American College of Neuropsychopharmacology. Pub lished by Elsevier Science Inc.