Calcium antagonists in elderly and black hypertensive patients. Therapeutic controversies.

Calcium antagonists are now recommended as monotherapy for the treatment of mild to moderate essential hypertension by the Joint National Committee (JNC) on the Detection, Evaluation, and Treatment of High Blood Pressure. Based on a statement in the 1988 JNC report that black and elderly patients tend to respond better to calcium antagonists, we reviewed the literature to examine the predictive value of age and race to the antihypertensive response of calcium antagonists. The majority of studies we reviewed failed to substantiate the JNC statement and well-promulgated reports in the literature suggesting preferential action of calcium antagonists in the elderly, or their superiority when compared with diuretics, beta-adrenergic blockers, and angiotensin-converting enzyme inhibitors. Although not noted by the JNC, pretreatment blood pressure appeared to be an important predictor of the antihypertensive response to calcium antagonists. The literature reviewed indicates that calcium antagonists have comparable efficacy in black and white hypertensive patients. However, the limited comparative studies reviewed support the JNC statement that, as with diuretics, blacks have a greater antihypertensive response with calcium antagonists than with beta-adrenergic blockers or angiotensin-converting enzyme inhibitors.

Norfloxacin does not alter warfarin's disposition or anticoagulant effect.

Drug interactions related to inhibition of hepatic drug metabolism have been identified for some fluoroquinolone antibiotics. This study was designed to investigate whether the fluoroquinolone norfloxacin at the usual clinical dosage interacts with the anticoagulant agent warfarin. Ten healthy male subjects were administered a single oral dose of 30 mg warfarin sodium alone or during multiple-dose treatment with norfloxacin, 400 mg bid, in a randomized, crossover fashion. Plasma warfarin concentrations and prothrombin times were measured for 6 days after each of the two warfarin doses. The pharmacokinetic parameters of warfarin were comparable in the absence and presence of norfloxacin, including no significant differences in warfarin's elimination half-life, apparent total clearance, apparent volume of distribution, or peak plasma concentration. Norfloxacin also had no significant effect on the anticoagulant effect of warfarin, as assessed by the area under the prothrombin time versus time curve and the maximum response for prothrombin time. The lack of pharmacokinetic or pharmacodynamic interaction observed in this study suggests that a clinically important interaction of norfloxacin and warfarin is unlikely to occur in patients requiring both drugs.