Individual responses to transdermal nitrates after chronic administration in angina pectoris

Intermittent or continuous transdermal nitroglycerin: still an issue, or is the case closed?

After a decade of controversy and debate, many experts have now concluded that continuous nitroglycerin patch treatment leads to complete tolerance development and therefore cannot be recommended for any angina patient. This conclusion is largely based on the disappointing results of the large Transdermal Nitroglycerin Cooperative Study, in which continuous patch treatment in doses of 15-105 mg daily failed to increase exercise duration more than placebo after 2 and 8 weeks of treatment. However, other well-designed studies recently reported maintained efficacy during continuous treatment, and the differences in results has remained unexplained. The disagreeing data may be better understood if certain facts are considered: (1) The cooperative study tested a patient population with a very low first-dose treatment response--only 34 seconds (or 10-12%) improvement compared with placebo. At the end of the study, 25% of the patients terminated exercise for reasons other than angina, and a reduced nitrate responsiveness had developed, even in the placebo group. (2) Patients who demonstrate a large first-dose nitrate responsiveness tend to be less susceptible to tolerance development. (3) Even during continuous therapy, maintained efficacy is often observed in exercise tests done 2-5 hours after patch renewal, while typically no effect is seen at the end of the application period. Attenuation of the initial effects is seen with all long-acting nitrate treatment regimens, but the degree of tolerance varies with the patient population, the efficacy parameter (exercise test vs. attack counts), the timing of the efficacy test, the patch dose, and whether or not nitrate-free (-low) intervals are used. In general, intermittent patch therapy is superior to continuous therapy in improving exercise duration, but even continuous therapy may retain some effect. Rebound phenomena do occur but are clinically relevant only in a minority of the patients. Rebound phenomena are not a problem during continuous therapy, which therefore may be of value in patients with frequent and/or nocturnal angina attacks. Patients experiencing angina during exercise only and with low first-dose effects are likely to benefit more from intermittent therapy. Doses of 0.6-0.8 mg/hr (15-20 mg/24 hr) are usually optimal, and the efficacy is comparable with that observed after oral nitrates.

Long-term efficacy of nitroglycerin patch in stable angina pectoris

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 the 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 less than 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.(ABSTRACT TRUNCATED AT 250 WORDS)