Nifedipine

Drugs. 2003;63(14):1435-44
Current treatment of patients with hypertension: therapeutic implications of INSIGHT
Taddei S, Ghiadoni L, Salvetti A
Department of Internal Medicine, University of Pisa, Pisa, Italy.

When planning treatment for patients with hypertension, current guidelines emphasise the importance of risk stratification, based on blood pressure, the presence of end-organ damage and other cardiovascular risk factors. Because the beneficial effect of antihypertensive therapy seems to be linked to the degree of blood pressure reduction, guidelines recommend reducing blood pressure below 140/90mm Hg, with a lower target in patients who are young or who have diabetes mellitus (with or without nephropathy) or non-diabetic nephropathy. Blood pressure reduction can be achieved with several classes of drugs, including diuretics, beta-blockers, ACE inhibitors, angiotensin II antagonists and calcium channel antagonists. Calcium channel antagonists have been shown to reduce the risk of stroke and major cardiovascular events. However, it is still controversial whether different treatment regimens based on different drug classes can offer advantages beyond similar degrees of blood pressure control in preventing cardiovascular morbidity and mortality. The International Nifedipine GITS Study: Intervention as a Goal in Hypertension Treatment (INSIGHT) was a controlled clinical trial aimed at comparing the efficacy of a long-acting calcium channel antagonist, nifedipine gastrointestinal-transport-system (GITS), versus co-amilozide, a combination of the diuretics hydrochlorothiazide (HCTZ) and amiloride, on morbidity and mortality in high-risk hypertensive patients. Nifedipine GITS and HCTZ/amiloride were equally effective at reducing blood pressure and the risk of primary outcomes (a composite of death from any cardiovascular or cerebrovascular cause, non-fatal stroke, myocardial infarction and heart failure). Results from other studies indicate that there may be greater benefits for stroke and smaller benefits for coronary artery disease with calcium channel antagonist-based regimens than with diuretic or beta-blocker-based regimens. However, there is at present insufficient evidence to recommend a specific drug choice based on patient risk profile. Thus, the choice of antihypertensive drug(s) should be according to efficacy and tolerability. In addition to the reductions in cardiovascular risk, two substudies of INSIGHT showed that nifedipine GITS was able to prevent the progression of intima media thickness in the common carotid artery and slow the progression of coronary calcification. The clinical significance of this effect in the prevention of cardiovascular events still remains to be established.

GENERIC NAME: nifedipine
BRAND NAMES: Adalat, Procardia

DRUG CLASS AND MECHANISM: Nifedipine belongs to a class of medications called calcium channel blockers. These medications block the transport of calcium into the smooth muscle cells lining the coronary arteries and other arteries of the body. Since calcium is important in muscle contraction, blocking calcium transport relaxes artery muscles and dilates coronary arteries and other arteries of the body. By relaxing coronary arteries, nifedipine is useful in treating and preventing chest pain (angina) resulting from coronary artery spasm. Relaxing the muscles lining the arteries of the rest of the body lowers the blood pressure, which reduces the burden on the heart as it pumps blood to the body. Reducing heart burden lessens the heart muscle's demand for oxygen, and further helps to prevent angina in patients with coronary artery disease. For more detailed information related to coronary artery disease, please visit the Chest Pain, Cholesterol, and Heart Attack articles.

PREPARATIONS: 10mg and 20mg capsules. Also available in extended release forms (Procardia XL, Adalat CC) in 30, 60, and 90mg capsules

STORAGE: Store at room temperature, avoid light and moisture.

PRESCRIBED FOR: Chest pain (angina) occurs because of insufficient oxygen delivered to the heart muscles. Insufficient oxygen may be a result of coronary artery blockage or spasm, or because of physical exertion which increases heart oxygen demand in a patient with coronary artery narrowing. Nifedipine is used for the treatment and prevention of angina resulting from coronary artery spasm as well as from exertion. Nifedipine is also used in the treatment of high blood pressure. It is also used to open the blood vessels which spasm, causing Raynaud's phenomenon.

DOSING: Nifedipine can be taken with or without food. Nifedipine is metabolized mainly by the liver and dosages may need to be lowered in patients with liver dysfunction.

DRUG INTERACTIONS: In patients with severe obstructive coronary artery disease, nifedipine can increase the frequency and severity of angina or actually cause a heart attack on rare occasions. This phenomenon usually occurs when first starting nifedipine, or at the time of dosage increase. Excessive lowering of blood pressure during initiation of nifedipine treatment can occur, especially in patients already taking another blood pressure lowering medication. In rare instances, congestive heart failure has been associated with nifedipine, usually in patients already on a beta blocker.

Administration of nifedipine with digoxin can increase digoxin blood levels. Therefore, blood levels of digoxin are usually monitored to avoid toxicity. Concurrent administration of cimetidine (Tagamet) interferes with the liver breakdown of nifedipine, and significantly increases nifedipine blood levels. Therefore, cautious dosing is necessary when both medications are administered. Generally, nifedipine is avoided in children.

PREGNANCY: Generally, nifedipine is avoided during pregnancy.

NURSING MOTHERS: 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 of nifedipine include headache, dizziness, flushing, and edema (swelling) of the lower extremities. Less common side effects include dizziness, nausea and constipation.

Caution! Before starting to take this medicine, it is vital that you should consult your doctor! Do not use it on your own initiative, without medical advice.