Nifedipine is a heart drug, marketed as Adalat by Bayer in the UK (Miles in the US), and as Procardia and XL by Pfizer in the US. It is used to treat relatively mild heart conditions, such as high blood pressure, and angina chest pain, usually cause

According to the US Physicians' Desk Reference, Nifedipine can bring about a heart attack. "Rarely, patients, particularly those [with severely blocked arteries] have developed well documented increased frequency, duration and/or severity of angina or acute [heart attack] on starting nifedipine or at the time of dosage increase," says the PDR. "The mechanism of this effect is not established."

The reason why it can make things worse are not the only things still unknown about this drug. Again, according to the PDR, nifedipine has been shown to help relieve angina that is brought on by physical exertion in controlled trials of up to eight weeks duration, "but confirmation of sustained effectiveness and evaluation of long term safety in these patients are incomplete" (our emphasis).

The PDR reports that in trials of over 1000 patients other reported side effects included edema the abnormal build up of fluid under the skin in up to a third of patients, plus headache, fatigue, dizziness, constipation and nausea.

Nifedipine can also cause abnormally low blood pressure, and its use should be carefully monitored in patients who are already taking other drugs which may also lower blood pressure.

It can also rarely cause congestive heart failure characterized by circulatory congestion and retention of salt and water by the kidneys particularly in patients taking beta blockers.