Nifedipine, known as a calcium channel blocker, is used to treat high blood pressure and some forms of chest pain known as angina. This medication works by relaxing blood vessels and decreasing the pressure on the heart. This can lead to dizziness, headache, lightheadedness, flushing and swelling of the legs. You should report this to your physician because it can often be easily treated with a diuretic (water-pill). This medication is available in an extended-release form allowing for once a day dosing. Some brands must be taken on an empty stomach. Other brands are made in porous capsule which slowly releases the medication. You may notice the empty capsule in your stool. Extended release medications should not be crushed, cut or split because this destroys the slow release mechanism. If you are taking this for high blood pressure, you should have your blood pressure checked regularly to make sure the medication is working.
Beta-adrenergic Blocking Agents: Experience in over 1400 patients in a non-comparative clinical trial has shown that concomitant administration of nifedipine and beta-blocking agents is usually well tolerated, but there have been occasional literature reports suggesting that the combination may increase the likelihood of congestive heart failure, severe hypotension or exacerbation of angina.
Long Acting Nitrates: Nifedipine may be safely co-administered with nitrates, but there have been no controlled studies to evaluate the antianginal effectiveness of this combination.
Digitalis: Immediate Release Capsules: Since there have been isolated reports of patients with elevated digoxin levels, and there is a possible interaction between digoxin and nifedipine, it is recommended that digoxin levels be monitored when initiating, adjusting, and discontinuing nifedipine to avoid possible over- or under-digitalization. Extended Release Tablets: Administration of nifedipine with digoxin increased digoxin levels in 9 of 12 normal volunteers. The average increase was 45%. Another investigator found no increase in digoxin levels in 13 patients with coronary artery disease. In an uncontrolled study of over 200 patients with congestive heart failure during which digoxin blood levels were not measured, digitalis toxicity was not observed. Since there have been isolated reports of patients with elevated digoxin levels, it is recommended that digoxin levels be monitored when initiating, adjusting, and discontinuing nifedipine to avoid possible over- or under-digitalization.
Quinidine: Immediate Release Capsules: There have been rare reports of an interaction between quinidine and nifedipine (with a decreased plasma level of quinidine).
Coumarin Anticoagulants: There have been rare reports of increased prothrombin time in patients taking coumarin anticoagulants to whom nifedipine was administered. However, the relationship to nifedipine therapy is uncertain.
Cimetidine: A study in 6 healthy volunteers has shown a significant increase in peak nifedipine plasma levels (80%) and area-under-the-curve (74%) after a 1 week course of cimetidine at 1000 mg per day and nifedipine at 40 mg per day. Ranitidine produced smaller, non-significant increases. The effect may be mediated by the known inhibition of cimetidine on hepatic cytochrome P-450, the enzyme system probably responsible for the first-pass metabolism of nifedipine. If nifedipine therapy is initiated in a patient currently receiving cimetidine, cautious titration is advised.
Known hypersensitivity reaction to nifedipine.