Streptokinase. A pharmacoeconomic appraisal of its use in the management of acute myocardial infarction

Abstract

Thrombolytic therapy with streptokinase and other agents reduces mortality and is now well accepted as the mainstay of revascularisation options for most patients after an acute myocardial infarction. Streptokinase is as efficacious as alteplase (recombinant tissue plasminogen activator; rt-PA) when given as a 3-hour infusion, anistreplase, reteplase and saruplase in reducing mortality. However, in the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO) trial, an accelerated alteplase regimen (1.5-hour infusion) plus intravenous heparin demonstrated a statistically significant 1% absolute mortality reduction compared with streptokinase plus heparin. Treatment with streptokinase is consistently clinically superior to conventional treatment and is cost effective: the marginal cost per year of life saved (cost/YLS) is less than $US/$Can20,000 (1990 or 1991 currency) assuming 5-year survival. In addition, streptokinase treatment is associated with fewer intensive care days and total days spent in hospital and a decrease in the use of intensive care services compared with conventional therapy. Importantly, the cost/YLS of treating older patients (70 to 80 years) with streptokinase is similar to that in younger patients (approximately $US22,000, 1990 currency). In 1 study, the cost of in-hospital treatment and associated 1-year follow-up costs did not differ significantly regardless of whether patients received streptokinase or anistreplase. In the most comprehensive cost-effectiveness analysis to date, GUSTO investigators determined that the incremental cost/YLS in patients who received the accelerated alteplase regimen instead of streptokinase was $US32,678 (1993 currency); the projected life expectancy was about 15 years. Thrombolytic therapy is generally more cost effective in patients at high risk than in those at low risk. The cost effectiveness of streptokinase is dependent on infarct location and time to treatment, but is more favorable in patients with anterior than inferior infarctions and those treated as soon as possible after symptom onset. There are as yet no comparative data to indicate a clinical benefit for one thrombolytic agent over another in patients treated more than 6 hours after symptom onset; therefore, in all likelihood, streptokinase will be preferred on the basis of cost minimisation. Streptokinase is associated with a slightly higher rate of severe bleeding than alteplase but a lower incidence of stroke. Although quality-of-life information comparing thrombolytics is unavailable, most patients who received streptokinase or alteplase rated their quality of life as high on the basis of results from time trade-off assessments and health surveys. In summary, streptokinase is undeniably cost effective compared with conventional treatment. It is up to individual healthcare systems to determine whether the mortality advantage and cost differential of the accelerated alteplase regimen over streptokinase, as seen in the GUSTO trial, are affordable and justifiable. However, it is important to realise that treatment options may be limited by healthcare resources; thus, streptokinase can be regarded as a cost-effective thrombolytic strategy which is both efficacious and affordable within the constraints of most healthcare budgets.