Nitroglycerine/N-acetylcysteine in the management of unstable angina pectoris.

N-acetylcysteine (NAC) has been shown to potentiate the haemodynamic and antiplatelet effects of nitroglycerine (NTG) in man, and to limit the development of haemodynamic tolerance to NTG. These effects may be mediated. by the formation of S-nitroso-NAC, which induces vasodilation and strongly inhibits platelet aggregation. In a randomized double-blind study in 46 patients with severe unstable angina pectoris unresponsive to standard treatment (including cutaneous nitrates and calcium antagonists in 45 patients) we compared the effects of intravenous (IV) NTG with those of IV NTG combined with IV NAC (5 g 6 hourly). Treatment with NTG/NAC (24 patients) was associated with a similar frequency of episodes of chest pain as treatment with NTG alone (22 patients), but somewhat fewer increments in infusion rate for pain control (10 vs 17; P NS). The NTG/NAC group had a significantly lower incidence of acute myocardial infarction than the NTG/placebo group (3 vs 10 patients; P = 0.013). Symptomatic hypotension occurred frequently in the NTG/NAC group (7 vs 0 patients; P = 0.006). It is concluded that combined administration of NTG and NAC in patients with unstable angina pectoris may augment the clinical efficacy of NTG, largely by reducing the incidence of acute myocardial infarction. However, the high incidence of severe hypotension with NTG/NAC suggests that this regimen should be used with some caution.