Low versus standard dose mCPP challenge in obsessive-compulsive patients

In several reports, the acute oral administration of the partial serotonergic agonist meta-chlorophenylpiperazine (mCPP) in dose of 0.5 mg/kg induced a significant worsening of obsessive-compulsive (OC) symptoms in a number of patients. The aim of our study was to test the 0.25 mg/kg mCPP dose, which was hypothesized to be more specific for OC symptoms and was until now tested only on healthy subjects. In a double-blind, controlled crossover study, 12 OC patients participated on three test days, receiving one of the following on each day: oral 0.5 mg/kg mCPP (standard dose), 0.25 mg/kg mCPP (low dose), or placebo. Behavioral ratings were obtained by means of Visual Analogue Scale (VAS) ratings. The low dose mCPP induced a significant worsening of OC symptoms in 50% (6/12) of the patients, whereas 8.3% (1/12) of the patients showed a worsening after the standard dose. On the other hand, only the standard dose mCPP induced a worsening, although not statistically significant, of anxiety ratings. Our data show that the 0.25 mg/kg dose mCPP induces a specific response in OC symptoms, with little anxiogenic effect. To confirm these preliminary data, future studies will be needed on larger samples and with more sensitive rating settles. (C) 2000 American College of Neuropsychopharmacology. Published by Elsevier Science Inc. Z8 0 ZR 0 ZS 0 ZB 16