Raised levels of antistreptokinase antibody and neutralization titres from 4 days to 54 months after administration of streptokinase or anistreplase.

Streptokinase and anistreplase are antigenic and their administration often leads to antibody formation. These can cause allergic reactions and/or neutralization of streptokinase with resulting suboptimal treatment. Currently, streptokinase re-administration is considered appropriate for up to 5 days and from 1 year after a previous dose. Antistreptokinase antibody and neutralization titres (NT) were measured in three groups of patients to determine if this practice is appropriate: 1. (early)--36 patients whose titres were measured for at least 5 days after thrombolysis; 2. (late)--57 patients who received thrombolysis 12-54 months previously; 3. (controls)--182 consecutive suspected myocardial infarction patients (without previous exposure to thrombolysis). Results were as follows (mean +/- SEM): 1. (early)--the antibody and/or NT were raised by day 4 in 19.4% of the patients. One patient could have neutralized 1.97 million units (MU) of streptokinase by day 4. (Day 4--antibody 1:39 +/- 11, NT 0.19 +/- 0.05 MU; day 5--1:136 +/- 41 and NT 0.7 +/- 0.43 MU respectively.) 2. (late)--23 patients (40%) had either antibody titres > or = 1:160 and/or NT > 1.5 MU. (12-23 months--antibody 1:243 +/- 43, NT 0.63 +/- 0.15 MU; 24-35 months--1:98 +/- 31 and 0.69 +/- 0.22 MU; 36-54 months--1:87 +/- 14 and 0.54 +/- 0.12 MU.) All titres were significantly higher than the controls (antibody 1:25 +/- 3, NT 0.14 +/- 0.01 MU, P < 0.01). After streptokinase or antistreplase, antibodies are raised from 4 days to at least 54 months. It would seem prudent to avoid their re-administration during this time interval.