Controversies in the use of transdermal nitroglycerin systems.

The role of transdermal nitroglycerin (TNTG) in the treatment of ischemic heart disease and congestive heart failure (CHF) is reviewed, with an emphasis on controversies concerning efficacy, hemodynamics, and dosing. Currently marketed rate-controlled transdermal nitroglycerin systems provide steady plasma concentrations of nitroglycerin for 24 hours. However, results of controlled trials in ischemic heart disease and CHF have raised doubts about the ability of TNTG to exert clinically important antianginal or hemodynamic benefit for the full 24-hour period. There is evidence that the duration of effect after TNTG application may persist for 24 hours, but there also is evidence of a lack of efficacy beyond 6 to 12 hours. This issue has not been resolved, but there is a trend toward use of larger doses that produce more persistent effects. The effects of conventional doses of TNTG in ischemic heart disease are modest; efficacy is based on demonstrated improvements in exercise performance. High TNTG doses (40-90 mg/24 hours) are required by many patients. In CHF, TNTG improves venous hemodynamic measurements. A dose-response relationship is not well defined. High-dose TNTG therapy is probably required to increase cardiac output and decrease systemic vascular resistance. Nitrate attenuation appears to be an important phenomenon with TNTG therapy. As with other forms of nitrate therapy, adverse effects may be a limiting factor, and clinical experience with high-dose TNTG therapy is limited. For some patients, TNTG therapy is an important addition to medical therapy. Further studies are needed to confirm reported improvements in exercise performance and hemodynamic benefits and to identify patient subsets likely to benefit from TNTG therapy.