Niaprazine
Niaprazine is a sedative-hypnotic drug of the phenylpiperazine group. It has been used in the treatment of sleep disturbances since the early 1970s in several European countries including France, Italy, and Luxembourg. It is commonly used with children and adolescents on account of its favorable safety and tolerability profile and lack of abuse potential.
Originally believed to act as an antihistamine and anticholinergic, niaprazine was later discovered to have low or no binding affinity for the H1 and muscarinic [acetylcholine receptor|mACh receptor]s, and was instead found to act as a potent and selective 5-HT2A and α1-adrenergic receptor antagonist. It possesses low or no affinity for the 5-HT1A, 5-HT2B, D2, and β-adrenergic, as well as at SERT and VMAT, but it does have some affinity for the α2-adrenergic receptor.
Niaprazine has been shown to metabolize to the compound para-fluorophenylpiperazine in a similar manner to how trazodone and nefazodone metabolize to meta-chlorophenylpiperazine. It is unclear what role, if any, pFPP plays in the clinical effects of niaprazine. However, from animal studies it is known that pFPP, unlike niaprazine, does not produce sedative effects, and instead exerts a behavioral profile indicative of serotonergic activation.