Calan (generic: verapamil) is a prescription medication used to treat chest pain, an irregular heartbeat, and high blood pressure. Calan SR, the extended release form of Calan, is used to treat only high blood pressure. Calan belongs to a group of drugs called calcium channel blockers, which work by relaxing the blood vessels, making it easier for the heart to pump blood.

Calan comes in an immediate release tablet form and is taken 3 to 4 times a day, with or without food.

Calan SR comes in an extended release tablet form and is taken 1 to 2 times a day with food.

Common side effects of Calan include constipation, nausea, low blood pressure, and headache. This medication can cause dizziness. Do not drive or operate heavy machinery until you know how Calan affects you.