Tolerance development during transdermal administration of nitroglycerin in angina pectoris

Nitroglycerin delivered by transdermal patch technology has been used in angina pectoris patients as well as in heart failure. In angina pectoris patients the plasma concentrations are low over the 24 hours. Effects can be found especially during the first 12 hours after application of the drug even during steady state conditions. The effect of the drug wanes after 24 hours and some studies suggest reduced effect when the patches have been applied for seven to 14 days. The attenuated effects have been claimed to be due to tolerance. Tolerance is, however, never absolute and in other studies this phenomenon is not shown. Furthermore, rebound phenomena may develop when nitroglycerin therapy is withdrawn. The optimal doses and schemes for nitroglycerin administration thus remain to be clarified.