Migraine pills. Box and blister packs of Dixarit pills used to prevent recurrent migraines. Each pill contains 25 micrograms of the drug clonidine hydrochloride. This drug acts as an antihypertensive, reducing blood pressure. Its use in preventing migraines has now largely been superceded by other drugs such as pizotifen. Side- effects of Dixarit include depression, sedation, dizziness and nausea.