What are some side effects of verapamil?

Possible side effects of verapamil include dizziness, slow heartbeat, constipation, upset stomach, nausea, headache and tiredness, according to WebMD. Serious side effects such severe dizziness, shortness of breath, swelling of ankles or feet, fainting or very slow heartbeat require medical attention.

Verapamil is a calcium channel blocker, as reported by MedicineNet. It works by blocking the entry of calcium into the muscle cells of the coronary arteries and causes the muscles to relax so that blood can flow more easily. This medicine is used to treat chest pain due to spasm of the coronary arteries and to lower high blood pressure.