Pizotifen (INN) or pizotyline (USAN), trade name Sandomigran, is a benzocycloheptene-based drug used as a medicine, primarily as a preventative to reduce the frequency of recurrent migraine headaches. Pizotifen is a serotonin antagonist acting mainly at the 5-HT2A and 5HT2C receptors. It also has some activity as an antihistamine as well as some anticholinergic activity. The main medical use for pizotifen is for the prevention of vascular headache including migraine and cluster headache. Pizotifen is one of a range of medications used for this purpose, other options include propranolol, topiramate, valproic acid and amitriptyline. While pizotifen is reasonably effective, its use is limited by side effects, principally drowsiness and weight gain, and it is usually not the first choice medicine for preventing migraines, instead being used as an alternative when other drugs have failed to be effective. It is not effective in relieving migraine attacks once in progress. Pizotifen has also been reported as highly effective in a severe case of erythromelalgia, a rare neurovascular disease that is sometimes refractory to the other drugs named above. Side effects include sedation, dry mouth, drowsiness, increased appetite and weight gain. Occasionally it may cause nausea, headaches, or dizziness. In rare cases, anxiety, aggression and depression may also occur. Pizotifen is well absorbed from the gastro-intestinal tract, peak plasma concentrations occurring approximately 5 hours after oral administration. The absorption of pizotifen is fast (absorption half life 0.5 to 0.8 hours) and nearly complete (80%). Over 90% is bound to plasma proteins. Pizotifen undergoes extensive metabolism. Over half of a dose is excreted in the urine, chiefly as metabolites; a significant proportion is excreted in the faeces. The primary metabolite of pizotifen (N-glucuronide conjugate) has a long elimination half-life of about 23 hours.