All drugs are used for treatment of OCD except:
Again, we have to choose between Carbamazepine and diazepam. Now, diazepam is a benzodiazepine and can improve anxiety temporarily however it doesn't act at core symptoms of OCD. Whereas, Carbamazepine, though has minimal evidence, but it has been found to act on core symptoms of OCD.
Carbamazepine
Lithium
Fluoxetine
Diazepam
Neurotic, Stress Related and Somatoform Disorders