Adalat

GENERIC NAME: nifedipine

BRAND NAMES: Adalat, Procardia, Afeditab, Nifediac

DRUG CLASS AND MECHANISM: Nifedipine belongs to a class of medications called calcium channel blockers (CCBs) that are used to treat angina (heart pain), high blood pressure, and abnormal heart rhythms. Other drugs in the same class include amlodipine (Norvasc), diltiazem (Cardizem LA, Tiazac), felodipine (Plendil), isradipine (Dynacirc), nicardipine (Cardene), nimodipine (Nimotop), and verapamil (Covera-HS, Veralan PM, Calan). Like other CCBs, nifedipine works by blocking the flow of calcium into the muscle cells surrounding the arteries that supply blood to the heart (coronary arteries) as well as other arteries of the body. Since the inflow of calcium is what causes the muscle cells to contract, blocking the entry of calcium relaxes the muscles and dilates (widens) the arteries. By dilating coronary arteries, nifedipine increases the flow of blood to the heart. This treats and prevents angina which occurs when the flow of blood to the heart is not adequate to supply the heart with enough oxygen necessary to pump blood. Relaxing the muscles surrounding other arteries of the body lowers blood pressure and thereby reduces the pressure against which the heart must pump blood and function. This reduces the demand of the heart for oxygen--another mechanism by which CCBs treat and prevent angina. In addition, nifedipine slows conduction of the electrical current that travels through the heart that causes the muscle of the heart to contract. This effect can be used to correct abnormally rapid heartbeats.

PRESCRIPTION: Yes

GENERIC AVAILABLE: Yes

PREPARATIONS: Capsules:10 and 20 mg. Tablets: 30, 60, and 90 mg

STORAGE: Tablets should be stored at room temperature 15-25 C (59-77 F). They should be protected from light, moisture, and humidity.

PRESCRIBED FOR: Nifedipine is used for the treatment and prevention of angina resulting from either an increased workload on the heart (as with exercise) or spasm of the coronary arteries. It is used in the treatment of high blood pressure, to treat abnormally fast heart rhythms such as atrial fibrillation, and in the prevention of episodes of rapid heart rhythm originating from the atria of the heart.

It also is used to dilate blood vessels that go into spasm such as those causing Raynaud's phenomenon, a painful condition of the hands caused by spasm of the arteries supplying blood to the hands. Non-FDA approved uses include anal fissures (applied to the fissures), prevention of migraine headaches in adults, ureteral stones (as secondary therapy) and wound healing (applied to the skin).

DOSING: The usual dose for nifedipine capsules is 10 to 20 mg three times daily. It is important to swallow capsules whole. For extended release tablets, the usual dose is 30 or 60 mg once daily. The tablets should be swallowed whole and not bitten or cut in half. Nifedipine can be taken with or without food.

DRUG INTERACTIONS: In rare instances, congestive heart failure has been associated with nifedipine, usually in patients already on a beta blocker, for example, propranolol (Inderal), metoprolol (Lopressor), etc. Excessive lowering of blood pressure (hypotension) during initiation of nifedipine treatment can occur, especially in patients already taking another blood pressure lowering drug.

Generally, nifedipine is avoided in children.

Nifedipine decreases the elimination of digoxin (Lanoxin) by the kidneys which can increase digoxin blood levels in the blood and give rise to digoxin toxicity. It is important, therefore, to monitor blood levels of digoxin in order to avoid toxicity.

Nifedipine interferes with the breakdown of tacrolimus (Prograf) by the liver, which in turn causes elevated blood levels of tacrolimus and may increase the risk of toxicity from tacrolimus.

Nifedipine reduces the blood levels of quinidine (Quinaglute, Quinidex, Quinora) which may reduce the effectiveness of quinidine. Conversely, blood levels of nifedipine are increased by quinidine and may lead to side effects from nifedipine.

Cimetidine (Tagamet) interferes with breakdown by the liver of nifedipine and increases nifedipine blood levels. Therefore, cautious dosing is necessary when both medications are administered concurrently.

Nifedipine should not be taken with grapefruit juice since grapefruit juice (one glass, approximately 200 ml) inhibits the breakdown of nifedipine by the liver and increases the levels of nifedipine in the blood.

PREGNANCY: There are no adequate studies of nifedipine in pregnant women, and in general, it is avoided during pregnancy.

NURSING MOTHERS: Nifedipine is excreted in human breast milk. Generally, nifedipine is avoided in nursing mothers.

SIDE EFFECTS: Side effects of nifedipine are generally mild, and reversible. Most side effects are expected consequences of the dilation of the arteries. The most common side effects include headache, dizziness, flushing, and edema (swelling) of the lower extremities. Less common side effects include dizziness, nausea and constipation.

Reference: FDA Prescribing Information