Verapamil and calcium-stimulated enzyme efflux from skeletal muscle.

An early and significant biochemical abnormality in Duchenne's muscular dystrophy is an increase in intracellular calcium. We have found that the "calcium-blocker" drug verapamil inhibits calcium-stimulated efflux of creatine kinase (EC 2.7.3.2) and lactate dehydrogenase (EC 1.1.1.27) in vitro from normal human skeletal muscle at therapeutic concentrations. Such a calcium blocker might therefore be useful in the treatment of Duchenne's muscular dystrophy.