Periactin® (cyproheptadine hydrochloride) is an antihistaminic and antiserotonergic agent. It acts as a 5-HT2 receptor antagonist and also blocks calcium channels. It is used in the treatment of allergies and is also used to stimulate appetite in underweight people (e.g. anorexia nervosa), however it also causes sedation. Sometimes it may be used to combat SSRI-induced sexual dysfunction, but is used cautiously in this manner due to the fact that it may reverse the effects of the SSRI. Cyproheptadine is also used, though rarely, as a prophylactic drug for migraine.