Myocardial biochemical modifications induced by theophylline with reference to its value as antianginal drug.

Theophylline-induced variations of cardiac metabolism have been investigated by determining concentrations of various energetic substrates and of high-energy phosphates in myocardial tissue, the repeated sampling of myocardium being made possible by an extracorporal circulation system. When administered in therapeutic, or even slightly higher doses, theophylline does not modify triglyceride, glycerol and free fatty acid content or phosphocreatine and ATP content in subepicardial and subendocardial layers, but it does lower glycogen and raise lactate concentration. Consequently, the changes in anaerobic glycolysis due to myocardial ischemia may be enhanced if, as is probably the case, theophylline fails to restore the supply of oxygen.