warnings
WARNINGS Excessive Hypotension Although, in most patients, the hypotensive effect of nifedipine is modest and well tolerated, occasional patients have had excessive and poorly tolerated hypotension. These responses have usually occurred during initial titration or at the time of subsequent upward dosage adjustment. Although patients have rarely experienced excessive hypotension on nifedipine alone, this may be more common in patients on concomitant beta-blocker therapy. Although not approved for this purpose, nifedipine and other immediate-release nifedipine capsules have been used (orally and sublingually) for acute reduction of blood pressure. Several well-documented reports describe cases of profound hypotension, myocardial infarction, and death when immediate-release nifedipine was used in this way. Nifedipine capsules should not be used for the acute reduction of blood pressure. Nifedipine and other immediate-release nifedipine capsules have also been used for the long-term control of essential hypertension, although no properly-controlled studies have been conducted to define an appropriate dose or dose interval for such treatment. Nifedipine capsules should not be used for the control of essential hypertension. Several well-controlled, randomized trials studied the use of immediate-release nifedipine in patients who had just sustained myocardial infarctions. In none of these trials did immediate-release nifedipine appear to provide any benefit. In some of the trials, patients who received immediate-release nifedipine had significantly worse outcomes than patients who received placebo. Nifedipine capsules should not be administered within the first week or two after myocardial infarction, and they should also be avoided in the setting of acute coronary syndrome (when infarction may be imminent). Severe hypotension and/or increased fluid volume requirements have been reported in patients receiving nifedipine together with a beta-blocking agent who underwent coronary artery bypass surgery using high dose fentanyl anesthesia. The interaction with high dose fentanyl appears to be due to the combination of nifedipine and a beta blocker, but the possibility that it may occur with nifedipine alone, with low doses of fentanyl, in other surgical procedures, or with other narcotic analgesics cannot be ruled out. In nifedipine treated patients where surgery using high dose fentanyl anesthesia is contemplated, the physician should be aware of these potential problems and, if the patient’s condition permits, sufficient time (at least 36 hours) should be allowed for nifedipine to be washed out of the body prior to surgery. Increased Angina and/or Myocardial Infarction Rarely, patients, particularly those who have severe obstructive coronary artery disease, have developed well documented increased frequency, duration and/or severity of angina or acute myocardial infarction on starting nifedipine or at the time of dosage increase. The mechanism of this effect is not established. Beta Blocker Withdrawal Patients recently withdrawn from beta blockers may develop a withdrawal syndrome with increased angina, probably related to increased sensitivity to catecholamines. Initiation of nifedipine treatment will not prevent this occurrence and might be expected to exacerbate it by provoking reflex catecholamine release. There have been occasional reports of increased angina in a setting of beta blocker withdrawal and nifedipine initiation. It is important to taper beta blockers if possible, rather than stopping them abruptly before beginning nifedipine. Congestive Heart Failure Rarely, patients, usually receiving a beta blocker, have developed heart failure after beginning nifedipine. Patients with tight aortic stenosis may be at greater risk for such an event, as the unloading effect of nifedipine would be expected to be of less benefit to these patients, owing to their fixed impedance to flow across the aortic valve.