Obsessive-compulsive disorder (OCD) affects 2-3% of the population and leads to a great deal of suffering. Many patients benefit from established treatments, the mainstay of which are cognitive behavioral therapy and a group of antidepressant medications known as serotonin reuptake inhibitors. However, 20-30% of patients get minimal benefit from these established therapeutic strategies. New avenues of treatment are urgently needed.

Existing medications for obsessive-compulsive disorder affect the neurotransmitters serotonin or dopamine; but increasing evidence suggests that functional disruptions of a different neurotransmitter, glutamate, may contribute to some cases of OCD. The investigators are therefore interested in using medications that target glutamate as novel treatment options for those OCD patients who do not benefit from established treatments.

One such medication is the drug riluzole, which is FDA approved for amyotrophic lateral sclerosis (ALS), or Lou Gehrig's disease, but may be of benefit to patients with psychiatric disorders due to its ability to moderate excessive glutamate. In preliminary studies, in which the investigators treated patients with riluzole (in addition to their established pharmacological regimen) in an open-label fashion (that is, without a placebo-treated control group), the investigators have found about 40-50% of patients to substantially improve over 2-3 months.

While immensely promising, these preliminary studies do not prove riluzole is truly a new beneficial medication for the treatment of OCD; a more rigorous placebo-controlled trial is needed for that purpose. The investigators are therefore now recruiting patients to participate in a double-blind, placebo-controlled trial of riluzole, added to whatever other OCD medications they are taking.