Pipamperone

Pipamperone (INN, USAN, BAN), sold under the brand name Dipiperon, is a typical antipsychotic of the butyrophenone family used in the treatment of schizophrenia and as a sleep aid for depression. It is or has been marketed under brand names including Dipiperon, Dipiperal, Piperonil, Piperonyl, and Propitan. Pipamperone was discovered at Janssen Pharmaceutica in 1961, and entered clinical trials in the United States in 1963.

Pharmacology
Pipamperone acts as an antagonist of the 5-HT2A, 5-HT2B, 5-HT2C D2, D3, D4, α1-adrenergic, and α2-adrenergic receptors. It shows much higher affinity for the 5-HT2A and D4 receptors over the D2 receptor (15-fold in the case of the D4 receptor, and even higher in the case of the 5-HT2A receptor), being regarded as "highly selective" for the former two sites at low doses. Pipamperone has low and likely insignificant affinity for the H1 and mACh receptors, as well as for other serotonin and dopamine receptors.

Pipamperone is considered to have been a forerunner to the atypical antipsychotics, if not an atypical antipsychotic itself, due to its prominent serotonin antagonism. It is also used to normalise mood and sleep patterns and has antianxiety effects in neurotic patients.

Antidepressant effects
Low-dose pipamperone (5 mg twice daily) has been found to accelerate and enhance the antidepressant effect of citalopram (40 mg once daily), in a combination (citalopram/pipamperone) referred to as PipCit (code name PNB-01).