Felodipine and Isradipine: New Calcium-Channel-Blocking Agents for the Treatment of Hypertension

The chemistry, pharmacology, pharmacokinetics, clinical uses, adverse effects, and dosage of felodipine and isradipine are reviewed. Felodipine and isradipine are new calcium-channel-blocking agents with FDA-approved labeling for use in the treatment of essential hypertension. Both agents are members of the dihydropyridine class of calcium antagonists, which also includes nifedipine and nicardipine. Like those agents, felodipine and isradipine affect blood pressure by producing peripheral vasodilation. Felodipine and isradipine undergo extensive first-pass metabolism; their bioavailabilities are approximately 15% and 17%, respectively. The drugs are highly protein bound but do not affect serum digoxin concentrations. Anticonvulsants may reduce the elimination half-life of felodipine. Felodipine and isradipine are effective antihypertensive agents when used alone or in combination with beta blockers or diuretics. Both agents have shown some benefit in the treatment of angina pectoris in limited studies. Clinical data do not support the use of either agent for the treatment of congestive heart failure or Raynaud's phenomenon. Felodipine and isradipine have similar adverse-effect profiles, and their adverse effects resemble those of other agents in the class. Common adverse effects are peripheral edema and increased heart rate. The initial dosage of isradipine for the treatment of hypertension is 2.5 mg twice daily. Felodipine should be started at a dosage of 5 mg once daily. Felodipine and isradipine are effective antihypertensive drugs but have not demonstrated clear advantages over other dihydropyridine calcium-channel blockers.