Cardiotoxicity of ritodrine: assessment based on serum creatine kinase activity.

: Thirty-three gravidas undergoing chronic tocolysis with ritodrine were assessed with respect to potential drug-induced cardiotoxic effects. The immunological and electrophoretic determination of serum creatine kinase activity gave no indication of such effects. The results of this study confirm the significant increase reported for the serum activity of the MB, BB, and MM creatine kinase isoenzymes during the post-partum period. In most cases no difference was found between the isoenzyme distribution pattern characterizing acute myocardial infarction and normal labor, and therefore the measurement of serum creatine kinase activity during labor has no value for the diagnosis of acute myocardial infarction.