Verapamil is used to treat angina pectoris (chest pain), high blood pressure, and irregular heartbeats (arrhythmia). It belongs to a group of drugs known as calcium channel blockers. It is not clearly understood how verapamil works, but it is thought to increase the blood supply to the heart.

Verapamil is also a vasodilator that relaxes the muscle tissue of the blood vessels, thereby lowering blood pressure.

Verapamil Facts
Brand names (manufacturers): Calan (Searle); Calan SR (Searle); Isoptin (Knoll); Isoptin SR (Knoll); verapamil (various manufacturers); Verelan (Lederle)

Type of drug: Antianginal (calcium channel blocker) and antihypertensive

Ingredient: Verapamil

Dosage forms: Tablets (40 mg, 80 mg, and 120 mg); sustained-
release tablets (120 mg,
180 mg, and 240 mg); sustained-release or extended-release capsules
(100 mg, 120 mg, 180 mg,
200 mg, 240 mg, and 360 mg)

Storage: Store at room temperature in a tightly closed container. Do not refrigerate it.

Treatment

Verapamil can be taken either on an empty stomach or with meals, as directed by your doctor or pharmacist. Do not crush or chew the sustained-release tablets or capsules; they must be swallowed whole.

The sustained-release and extended-release capsules may
be opened and the contents sprinkled onto a spoonful of applesauce that is either at room temperature or cold from
the refrigerator (not hot). After swallowing this mixture, be
sure to drink a glass of water to ensure that all the pellets
have been swallowed. Never crush or chew the pellets. Do
not prepare the applesauce-pellet mixture ahead of time. It
must be taken immediately after it is prepared.

If you miss a dose of verapamil, take the missed dose as
soon as possible. However, if it is almost time for the next
dose, do not take the missed dose at all; just return to your regular dosing schedule. Do not double the next dose.

Verapamil does not cure your medical condition, but it will
help to control the condition as long as you continue to
take it.

Side Effects

Minor: Abdominal pain, blurred vision, constipation, dizziness, headache, muscle cramps, nausea, sleeplessness, or sweating. These side effects should disappear as your body adjusts to verapamil.

To relieve constipation, increase the amount of fiber in your diet (fresh fruits and vegetables, salads, bran, and whole-grain breads), and drink more water (unless your doctor directs you to do otherwise).

If verapamil makes you feel dizzy, sit or lie down for a while, get up slowly from a sitting or reclining position, and be careful on stairs.

To avoid dizziness when you stand, contract and relax the muscles of your legs for a few moments before rising. Do this by pressing one foot against the floor while raising the other foot slightly, alternating feet so that you are "pumping" your legs in a pedaling motion.

In addition, to help prevent dizziness or fainting while taking verapamil, try not to stand for long periods of time, avoid drinking alcoholic beverages, and try not to become overheated (avoid exerting yourself or exercising strenuously in hot weather, and do not take hot baths, showers, or saunas).

Major: Tell your doctor about any side effects that are persistent or particularly bothersome. IT IS ESPECIALLY IMPORTANT TO TELL YOUR DOCTOR about changes in menstruation, confusion, depression, fainting, fatigue, hair loss, itching, loss of balance, palpitations, rapid weight gain (three to five pounds within a week), shortness of breath, swelling of the hands or feet, tremors, or unusual weakness.

Interactions

Verapamil will interact with a number of other types of medications:

  • The concurrent use of alcohol, quinidine, or prazosin and verapamil can cause a severe drop in blood pressure and result in fainting.

  • Beta blockers (acebutolol, atenolol, betaxolol, carteolol, esmolol, labetalol, metoprolol, nadolol, penbutolol, pindolol, propranolol, or timolol) and digoxin should be used cautiously with verapamil, because side effects to the heart may be increased.

  • Disopyramide should not be taken within 48 hours of verapamil; the combination of these medications could lead to heart failure.

  • Cimetidine and ranitidine can decrease the elimination of verapamil from the body, which can lead to an increased risk of side effects.

  • Sulfinpyrazone and rifampin can increase the elimination of verapamil from the body, which can lead to a decrease in its effectiveness.

  • Verapamil can increase the effects of carbamazepine, theophylline, cyclosporine, sirolimus, tacrolimus, amiodarone, prazosin, and drugs that treat high cholesterol (including lovastatin, atorvastatin, and pravastatin).

BE SURE TO TELL YOUR DOCTOR about any medications you are taking.

Warnings

  • Tell your doctor about unusual or allergic reactions you have had to any medications, especially to verapamil.

  • Before starting therapy with verapamil, be sure to tell your doctor if you have ever had any type of heart disease, kidney disease, liver disease, low blood pressure, or a slowed heartbeat.

  • Your doctor may want you to check your pulse while you are taking verapamil. If your heart rate drops below 50 beats per minute, contact your doctor.

  • Verapamil is not effective for an attack of chest pain that has already started; this medication is only effective in preventing attacks from occurring.

  • It is extremely important that you do not stop taking verapamil without first consulting your doctor. Stopping abruptly may lead to a worsening of your chest pain. Your doctor may, therefore, want to reduce your dosage gradually or have you switch to another similar medication when verapamil is discontinued.

  • Do not become concerned if you notice the outer shell of certain verapamil tablets in your stools. This is normal and to be expected.

  • Be sure to tell your doctor if you are pregnant. Extensive studies in pregnant women have not been conducted. Also be sure to tell your doctor if you are breast-feeding an infant. Small amounts of verapamil pass into breast milk and may cause unwanted side effects in the nursing infant.