Effects of nifedipine and nicardipine on regional cerebral blood flow distribution in patients with arterial hypertension.

Regional cerebral blood flow (rCBF) in 75 patients with arterial hypertension and symptoms of chronic ischemic cerebrovascular disorders was studied by using the 133Xenon infusion technique and a 30-detector setup. A baseline decrease in the mean hemispheric blood flow (rCBFh) with elevated deviations of rCBF from rCBFh were observed in the hemispheres. A single oral dose of either nifedipine or nicardipine induced various changes in rCBF. The drug effects regarding changes in the mean value of the hemispheric blood flow and the flow distribution were classified into 4 types. A decrease in the deviation of rCBF from the hemispheric mean CBF accompanied by an increase in the total brain blood flow was considered to be the most beneficial drug effect. This positive reaction was found more frequently when patients were given nicardipine. In some patients both drugs induced nonbeneficial changes in rCBF with an increase in the number of ischemic and hyperemic regions. It was hypothesized that such variants of drug effects may result in the deterioration of brain perfusion, contributing to development of focal brain ischemic damages. The effects of drugs were similar after both single doses and 2-week monotherapy. It is suggested that the analysis of drug effects on regional CBF distribution may be useful for estimating clinical importance of changes in cerebral hemodynamics during antihypertensive therapy.