Verapamil (Isoptin / Calan Generic) for Angina Pectoris

  • Type of Drug: Calcium channel blocker.
  • Prescribed for: Angina pectoris and Prinzmetals’s angina, high blood pressure, abnormal heart rhythms, asthma, cardiomyopathy, migraine headaches, nighttime leg cramps, and manic depression.
  • Brand Name: Calan/Calan SR , Isoptin/Isoptin SR, Verelan Sustained-Release Capsules.

General Information of Verapamil Generic

Verapamil is one of several calcium channel blockers available in the United States. These drugs work by blocking the passage of calcium into heart and smooth muscle. Since calcium is an essential ingredient in muscle contraction, blocking calcium reduces both muscle contraction and oxygen use by the muscle. This is why Verapamil is used in the treatment of angina, a kind of heart pain related to. poor oxygen supply to the heart muscles. Verapamil also dilates (widens) the vessels that supply blood to the heart muscles and prevents spasm of these arteries. Verapamil affects the movement of calcium only into muscle cells; it does not have any effect on calcium in the blood. Verapamil brands with “SR” after their name are sustained-release formulas. They should be used only for high blood pressure. Other calcium channel blockers may also be prescribed for Raynaud’s syndrome and congestive heart failure.

Cautions and Warnings

Verapamil may cause lowered blood pressure in some patients. Patients taking a beta-blocking drug who begin taking Verapamil may develop heart failure. Do not take this drug if you have had an allergic reaction to it.

Verapamil may cause angina pain when treatment is first started, when dosage is increased, or if the drug is rapidly withdrawn. This can be avoided by gradual dosage reduction.

Studies have shown that people taking calcium channel blockers (usually those taken several times a day, not those that are taken only once daily) have a greater chance of having a heart attack than people taking beta blockers or other medicines for the same purposes. Discuss this with your doctor to be sure you are receiving the best possible treatment.

In small numbers of people, Verapamil can interfere with the movement of nervous impulses within the heart, leading to an unusual slowing of heart rate.

People with hypertrophic cardiomyopathy, a condition in which heart muscle is progressively weakened and destroyed, who are receiving up to 720 mg a day of Verapamil are at risk of developing severe cardiac side effects. Most of these effects respond to dosage reduction, and people generally can continue on Verapamil at a lower dose.

People with severe liver disease break down Verapamil much more slowly than people with less severe disease or normal livers. Your doctor should take this into account when determining your daily Verapamil dosage. Caution is recommended in people with severe kidney disease, though dose adjustment may not be needed.

Verapamil may slow the transmission of nerve impulses to muscle in people with Duchenne’s muscular dystrophy, possibly causing respiratory muscle failure. Reduced Verapamil dosage may, be needed.

Possible Side Effects of Verapamil

Calcium-channel-blocker side effects are generally mild and rarely cause people to stop taking them. Verapamil generally causes fewer side effects than most other calcium channel blockers.

  • Most common: skin rash; low blood pressure; slowed heartbeat; heart failure or lung congestion (leading to coughing, wheezing, or breathing difficulty); tiredness or weakness; swelling of the ankles, feet, or legs; headache; dizziness; right-headedness; constipation; and nausea.
  • Rare: chest pain, rapid or irregular heartbeat, unusual production of breast milk, bleeding or tender gums, fainting, flushing or feeling warm.
  • Other rare side effects have affected a variety of body systems. Report anything unusual to your doctor.
    In addition, some patients taking Verapamil have experienced heart attack and abnormal heart rhythms, but the occurrence of these effects has not been directly linked to Verapamil.

Verapamil Drug Interactions

  • Long-term Verapamil use will cause the levels of Digoxin and Digitoxin drugs in the blood to increase by 50 to 70 percent. The dose of these drugs will have to be drastically lowered if Verapamil is added.
  • Disopyramide should; not be taken within 48 hours of taking Verapamil, because of possible interaction.
  • Patients taking Verapamil together with Quinidine may experience very low blood pressure, slow heartbeat, and fluid in the lungs.
  • Verapamil’s effectiveness and its side effects may be reversed by taking calcium products (including antacids).
  • Verapamil may interact with beta-blocking drugs to cause heart failure, very low blood pressure, or increased angina pain. However, in many cases these drugs have been taken together with no problem. Low blood pressure can also result from taking Verapamil with Fentanyl, a narcotic pain reliever.
  • Through interaction with other antihypertensive drugs, Verapamil may cause unexpected blood pressure reduction in patients already taking medicine to control their high blood pressure.
  • Cimetidine and Ranitidine increase the amount of Verapamil in the blood and may account for a slight increase in its effect.
  • The combination of Dantrolene and Verapamil can lead to high blood-calcium levels and heart muscle depression. If you are taking Dantrolene, a calcium channel blocker other than Verapamil should be precribed by your doctor.
  • Verapamil can increase the effects of Carbamazepine, Cyclosporine, and Theophylline products, increasing the chance of side effects with those drugs.
  • Verapamil may decrease the amount of Lithium in your body, leading to a possible loss of antimanic control, Lithium toxicity, and psychotic symptoms.
  • Rifampin, barbiturates, Phenytoin and similar antiseizure medicines, vitamin D, and Sulfinpyrazone may decrease the amount of Verapamil in your blood and its effect on your body.

Food Interactions

Take regular Verapamil tablets at least 1 hour before or 2 hours after meals.

Sustained-release Verapamil products may be taken without regard to food or meals. Take them with food if they upset your stomach.

Usual Dose of Verapamil

120 to 480 mg a day, individualized to patient need.


Overdosage of Verapamil can cause low blood pressure. Symptoms are dizziness, weakness, and (possibly) slowed heartbeat. If you have taken an overdose of Verapamil, call your doctor or go to a hospital emergency room. ALWAYS bring the medicine bottle with you.

Verapamil Special Information

Call your doctor if you develop abnormal heart rhythm, swelling in the arms or legs, difficulty breathing, increased heart pains, dizziness, light-headedness, or low blood pressure. Do not stop taking Verapamil abruptly.

If you forget to take a dose of Verapamil, take it as soon as you remember. If it is almost time for your next regularly scheduled dose, skip the one you forgot and continue with your regular schedule. Do not take a double dose.

Special Populations

Verapamil may cause birth defects or interfere with your baby’s development. Check with your doctor before taking it if you are, or might be, pregnant.
Verapamil passes into breast milk. Taking Verapamil during nursing may cause problems; nursing mothers should take the drug only if absolutely necessary.

Older adults are more sensitive to the side effects of Verapamil and are more likely to develop low blood pressure while taking it. Follow your doctor’s directions and report any side effects at once.