Augmentation of serum CPK activity by digitalis in patients with acute myocardial infarction.

The effect of acetyl strophanthanin on the rate of creatine phosphokinase (CPK) efflux was evaluated in 59 predominantly class I and II patients randomly allocated between treated and control. Therapy (0.5 mg) was begun 11-15 hours after the onset of symptoms and repeated four hours later (0.25 mg). Accumulated CPK activity (ACA) was determined from serial serum CPK changes sampled every two hours and compared to predicted CPK activity (PCA) determined from the first seven hours of CPK changes. In the control group, ACA was not significantly different from PCA. Digitalis consistently resulted in an augmentation of CPK efflux into serum which was temporally related to drug administration and resulted in a corresponding increase in ACA (P less than 0.001). Thus acetyl strophanthanin appears to increase apparent CPK activity in serum in class I and II patients.