DRUG REACTIONS Aspirin antagonises mortality effects of enalapril in MI

Although use of either aspirin or enalapril is beneficial in terms of reducing mortality in patients following myocardial infarction (MI), investigators from Norway have found that concomitant use of aspirin antagonises the effect of enalapril on mortality in such patients.

The investigators reanalysed data on 6090 patients with acute MI from the Cooperative New Scandinavian Enalapril Survival Study II (CONSENSUS II) to examine the· effect of an enalapril-aspirin interaction on long-term mortality. All patients received enalapril; 4697 were receiving aspirin at randomisation and 1393 were not receiving aspirin.

A significant negative interaction between enalapril and aspirin was found in both a multiplicative and additive model. In the multiplicative model, the effect of enalapril on late mortality (within 6 months after randomisation) was significantly better in patients not receiving aspirin, than in those receiving aspirin, at randomisation; this interaction was of borderline significance for 30-day (early) mortality. The additive model showed a significant additive enalapril-aspirin interaction regarding late, but not early, mortality. The 6-month mortality synergy index* was < 1 (0.70; 95% CI 0.46-0.94), thus indicating antagonism. * The synergy index was calculated as the ratio of the observed effect on mortality of concomitant enalapril + aspirin exposure to the effect predictedfrom the swn of the effects of enaJapril and aspirin acting separately.

Nguyen KN. Aursnes I, Kjekshus J. Interaction between enalapril and aspirin on mortality after acute myocardial infarction: subgroup analysis of the Cooperative New Scandinavian Enalapril Survival Study n (CONSENSUS 11). Atuerican Journal of Cardiology 79: 115-119. 15 Jan 1997 800497721

1173·8324197/1074-000211$01.00° Adls International Llmltad 1997. All rights reserved

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Inpharma'"15 Feb 1997 No. 1074