[The development of nifedipine tolerance during its regular dosage in patients with stable exertional stenocardia]

The possibility of the development of tolerance to anti-ischemic effects of nifedipine (NF) during chronic administration for 2 months was studied in 15 patients with stable angina pectoris of effort. The duration and degree of the anti-ischemic effect were assessed in terms of similar, individually adjusted exercises performed prior to and repeatedly after NF administration. After acute NF administration the anti-ischemic effect lasting at least 4 h (mean 5.4 +/- 0.4 h) was attained in all the patients. After 2 months of regular NF administration the duration of the NF anti-ischemic effect significantly decreased to 3.9 +/- 0.5 h. In 5 patients, the attenuation of NF efficacy turned out substantial. The study performed 8-10 days after NF withdrawal in those 5 patients revealed partial restoration of the effect. The development of tolerance to NF action was not associated with changes in NF and its metabolite plasma concentrations. NF binding to plasma proteins also remained constant during the study.