[Tolerance for the antianginal effect of nitrates. Approaches to its study]

Fifteen patients with coronary heart disease and stable angina pectoris of effort were examined for tolerance to the antianginal effect of isosorbide dinitrate (ID) taken permanently. After 6 weeks of treatment with ID in doses selected on an individual basis the antianginal effect evaluated by bicycle ergometry before and after ID intake remained stable. Sixty per cent of the patients showed a decrease in the drug effect, while in 40 per cent of the patients that decrease was moderate (partial ID tolerance) and in 20 per cent considerable (marked ID tolerance). After the drug dose was twice as raised the patients also remained drug tolerant.