Dopamine blocking activity of clomipramine in patients with obsessive-compulsive disorder.

While many data suggest that Obsessive-Compulsive Disorder (OCD) is an illness accompanied by dysregulation of the serotonergic system, interesting clinical evidence and animal studies also suggest possible dysregulation of the dopaminergic (DA) system. In order to determine whether clomipramine (CMI), an antiobsessional agent, is capable of altering DA function, we performed a neuroleptic radioreceptor assay (NRRA) on plasma samples from OCD patients before and after treatment in a double-blind, placebo controlled trial of CMI. CMI produced mild but significant DA D-2 receptor binding activity in an in vitro assay. The degree of dopamine binding activity did not correlate with clinical response to clomipramine. Because it has been suggested that another drug with antiobsessional efficacy, fluoxetine, may also have dopamine blocking properties, it may be speculated that antidopaminergic activity in combination with serotonergic effects is involved in antiobsessional activity of effective agents for some patients.