PRE-DOSING ANTIBODY-LEVELS AND EFFICACY OF THROMBOLYTIC DRUGS CONTAINING STREPTOKINASE

Objective-To evaluate the influence of pretreatment streptokinase resi stance titre and the concentration of IgG antibodies to streptokinase on the efficacy of thrombolytic drugs containing streptokinase in rest oring coronary patency in acute myocardial infarction. Design-Comparat ive observational study. Setting-City general hospital. Patients-One h undred and twenty four previously unexposed patients presenting within six hours of onset of acute myocardial infarction. Interventions-Stre ptokinase, 1.5 MIU as intravenous infusion over 60 minutes (60 patient s), or anistreplase, 30 units as intravenous injection over five minut es (64 patients). Main outcome measures-Pretreatment streptokinase res istance titre and concentration of IgG antibodies to streptokinase wer e measured in 96 and 124 patients respectively and coronary patency as sessed angiographically at 90 minutes and 24 hours. Results-Pretreatme nt streptokinase resistance titre and concentrations of IgG antibodies to streptokinase were low and skewed towards higher values. Those pat ients with coronary occlusion at 24 hours had a significantly higher m edian streptokinase resistance titre (100 v 50 streptokinase IU ml(-1) , P = 0.02). There were trends towards a higher streptokinase resistan ce titre in those patients with coronary occlusion at 90 minutes (50 v 20 streptokinase IU ml(-1), P = 0.06) and higher concentrations of Ig G antibodies to streptokinase in those with coronary occlusion at both 90 minutes and 24 hours (1.53 v 0.925, P = 0.03; 1.65 v 1.04 mu g str eptokinase binding ml(-1), P = 0.06). Coronary patency rates were simi lar in the two treatment groups. Conclusions-In the range measured in previously unexposed patients the streptokinase resistance titre has a small, but significant, negative influence on the efficacy of strepto kinase and anistreplase. This effect should be considered if retreatme nt with streptokinase or anistreplase is proposed.