Comparative evaluation of the effects of isradipine and diltiazem on antipyrine and indocyanine green clearances in elderly volunteers

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Abstract
Calcium antagonists have been shown to depress hepatic enzymes and accelerate hepatic blood flow. This study was designed to compare the effects of two calcium antagonists, isradipine and diltiazem, on antipyrine and indocyanine green (ICG) clearances in the elderly. Eighteen elderly subjects (aged 65 to 80 years) received either isradipine (5 mg every 12 hours), diltiazem (90 mg every 8 hours), or placebo (every 12 hours) for 4 days. On the third day after the study treatment, a 0.5 mg/kg dose of ICG was administered. Blood samples were obtained over 20 minutes for HPLC determination of ICG plasma concentrations. Ten minutes later, subjects ingested 1.2 gm antipyrine. Blood samples were obtained over 48 hours for HPLC determination of antipyrine plasma concentrations. Mean .+-. SD antipyrine clearance after diltiazem (0.0258 .+-. 0.0065 L/hr/kg) was significantly lower than that observed after isradipine (0.0334 .+-. 0.0098 L/hr/kg) or placebo (0.0329 .+-. 0.0082 L/hr/kg). Antipyrine clearance after isradipine was not significantly different from that after placebo. Mean .+-. SD ICG clearances after diltiazem (9.17 .+-. 1.35 ml/min/kg) or isradipine (9.57 .+-. 1.82 ml/min/kg) were significantly higher than that observed after placebo (8.06 .+-. 1.45 ml/min/kg). These findings suggest that diltiazem, but not isradipine, affects hepatic enzyme activity in the elderly. Both agents accelerate ICG clearance, a marker of hepatic blood flow.