Adalat Disease Interactions

The use of some calcium channel blockers (CCBs) is contraindicated in patients with advanced aortic stenosis. CCBs whose pharmacologic effect is partially dependent on their ability to reduce afterload (e.g., diltiazem, nicardipine, nifedipine, verapamil) may be of less benefit in these patients due to a fixed impedance to flow across the aortic valve and may, in fact, worsen rather than improve myocardial oxygen balance. Rarely, heart failure has developed following the initiation of these CCBs, particularly in patients receiving concomitant beta-blocker therapy.

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In general, calcium channel blockers (CCBs) should not be used in patients with hypotension (systolic pressure < 90 mm Hg) or cardiogenic shock. Due to potential negative inotropic and peripheral vasodilating effects, the use of CCBs may further depress cardiac output and blood pressure, which can be detrimental in these patients. The use of verapamil and diltiazem is specifically contraindicated under these circumstances.

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Increased frequency, duration, and/or severity of angina, as well as acute myocardial infarction, have rarely developed during initiation or dosage increase of calcium channel blockers (CCBs), particularly in patients with severe obstructive coronary artery disease and those treated with immediate-release formulations. The mechanism of this effect is not established. Therapy with CCBs should be administered cautiously in patients with significant coronary artery disease.

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Calcium channel blockers (CCBs) are extensively metabolized by the liver. The half-lives of CCBs may be prolonged substantially in patients with severe hepatic impairment, with the potential for significant drug accumulation. In addition, the use of some CCBs has been associated with elevations in serum transaminases, both with and without concomitant elevations in alkaline phosphatase and bilirubin. While these effects may be transient and reversible, some patients have developed cholestasis or hepatocellular injury. Therapy with CCBs should be administered cautiously and often at reduced dosages in patients with significantly impaired hepatic function. Periodic monitoring of liver function is advised.

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For the long-term treatment of hypertension, only the extended-release formulations of nifedipine should be used. The US National Heart, Lung, and Blood Institute and the FDA Cardiovascular and Renal Drug Advisory Committee have issued warnings against the use of immediate-release nifedipine for this purpose based on review of three epidemiologic studies of patients with hypertension and unstable angina who were treated with calcium channel blockers (CCBs) and at least two meta-analyses of randomized, controlled trials that included patients receiving CCBs. Two of the case-control studies found an increased risk of myocardial infarction (MI) in patients taking immediate-release nifedipine, although the third did not.

The use of immediate-release nifedipine (orally or sublingually) is also contraindicated for acute reduction of blood pressure. Profound hypotension, acute myocardial infarction, and deaths have been reported when nifedipine was used in this manner.

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Clinical trials studying the use of immediate-release nifedipine in patients who had just sustained myocardial infarctions have not demonstrated any benefit. In fact, in some trials, patients who received immediate-release nifedipine had significantly worse outcomes than patients who received placebo. The manufacturers state that immediate-release formulations of nifedipine should not be administered for 1 week after myocardial infarction. They should also be avoided in the setting of acute coronary syndrome, when infarction may be imminent.

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Calcium channel blockers (CCBs) may have varying degrees of negative inotropic effect. Congestive heart failure (CHF), worsening of CHF, and pulmonary edema have occurred in some patients treated with a CCB, primarily verapamil. Some CCBs have also caused mild to moderate peripheral edema due to localized vasodilation of dependent arterioles and small blood vessels, which can be confused with the effects of increasing left ventricular dysfunction. Although some CCBs have been used in the treatment of CHF, therapy with CCBs should be administered cautiously in patients with severe left ventricular dysfunction (e.g., ejection fraction < 30%) or moderate to severe symptoms of cardiac failure and in patients with any degree of ventricular dysfunction if they are receiving a beta-adrenergic blocker. Likewise, caution is advised in patients with acute myocardial infarction and pulmonary congestion documented by X-ray on admission, since associated heart failure may be acutely worsened by administration of a CCB.

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Although the clearance of nifedipine is not dependent on renal function, use of the drug in patients with uremia has been associated with enhanced pharmacologic effects, possibly due to increased sensitivity to the drug or reduced protein binding. Rarely, reversible elevations in BUN and serum creatinine have been reported in patients with preexisting chronic renal insufficiency given nifedipine, although a causal relationship has not been established. Nephritis and renal failure have also been observed. Therapy with nifedipine should be administered cautiously in patients with significantly impaired renal function.

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The extended-release formulation of nifedipine (Procardia XL) contains a non-deformable material. There have been rare reports of obstructive symptoms in patients with known strictures following the ingestion of similar sustained-release products. Therapy with the extended-release formulation of nifedipine should be administered cautiously in patients with preexisting severe gastrointestinal narrowing or obstruction, whether pathologic or iatrogenic.

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