Long-term efficacy of nitroglycerin patch in stable angina pectoris

Abstract

Subchronic and chronic efficacy of a 10 mg of nitroglycerin (NTG) patch was studied in 30 patients with stable angina pectoris. The trial consisted of 2 periods of study: 1 period of 2 months with a double-blind, crossover, placebo-controlled design and a second period of open treatment with verum patch. Two 7-day washout periods were performed at entry and at the end of the study. Efficacy was evaluated by clinical assessment of anginal attacks and NTG consumption and by means of multistage treadmill exercise testing. Exercise tests were performed at time 0 (24 hours from application of last patch), at 4 and 12 hours after dosing at the end of first 7-day washout, at the end of first month of treatment, at the end of the second month of treatment after crossover, at the end of 3 months of treatment with active patch and at the end of the second 7-day washout period. Statistics were obtained by multivariate analysis of difference. In 27 patients whose records were available for final analysis the daily attacks of angina and NTG consumption decreased significantly during both the subchronic and chronic phases of the trial compared with placebo (p < 0.001). Subchronic study showed significant improvement of maximal exercise duration, time to onset of angina, time to ST-segment depression of 1.0 mm, time to regression of angina and time to regression of ST depression, compared with placebo. The efficacy was maintained during 3 months of chronic therapy but a certain degree of attenuation of effects was observed for some parameters: Duration of exercise and time of onset of angina was slightly but not significantly reduced during the chronic compared with the subchronic phase; time to regression of angina and ST-segment depression significantly increased at the end of the chronic trial compared with results in the subchronic phase. Thus, some degree of attenuation of effects occurred but not to a degree that would abolish all beneficial effects of treatment with NTG patch. The association with other drugs, for which the dosing regimen was maintained constantly throughout the entire study, may be one of the possible explanations for lack of tolerance in our study.