Nifedipine plasma concentration in patients treated for angina pectoris.

Nifedipine, a "calcium channel blocker", is increasingly employed in the treatment of angina pectoris. Large interindividual differences have been observed in the effective dosage of the drug. Many of the reported alleged adverse reactions to nifedipine are linked to its primary pharmacologic action - vasodilatation. Therefore in 15 patients with angina pectoris we studied the relation between nifedipine concentration in the plasma and its clinical effects. Although in individual patients an increase in daily dose from 30 to 50 mg was followed by increased plasma levels and cessation of anginal attacks, no "therapeutic plasma range" could be delineated. Similarly, although some patients developed a headache when relatively high levels were measured, these levels still overlapped with those found in asymptomatic patients.