Abstract: Disclosed are methods for inhibiting the side effects attendant treatment with HMG-CoA reductase inhibitors. Treatment of a patient with and HMG-CoA reductase inhibitor in combination with coenzyme Q.sub.10 provides a reduction in patient cholesterol levels and guards against typical HMG-CoA reductase-inhibitor side effects, most notably liver dysfunction and cardiac dysfunction. The combination of lovastatin, an HMG-CoA reductase inhibitor, and coenzyme Q.sub.10 in ratios of between 1:2 to 1:29 provide significant enhancement of a patient's caridac condition. By way of example, other HMG-CoA reductase inhibitors which may be included in the claimed combinations include pravastatin, compactin, fluvastatin, dalvastatin, simvastatin, BMY 22089, GR-95030, HR-780, CI-981, SQ 33,600, and BMY 22566 and XU-62-320.