Novel Phosphodiesterase Type 5 Inhibitors: Assessing Hemodynamic Effects and Safety Parameters

Abstract

The relaxing effect of the phosphodiesterase type 5 (PDE5) inhibitors on vascular smooth muscle has attracted much attention, especially in persons with cardiovascular disease. The results of early studies showed that sildenafil slightly reduces systolic and diastolic blood pressures and has no effect on heart rate, while being safe and well tolerated. Studies also indicate that sildenafil does not contribute to the development of myocardial infarction or ischemia. Similar benign effects on hemodynamics and cardiac events have also been demonstrated for tadalafil and vardenafil. None of the PDE5 inhibitors adversely affects total exercise time or time to ischemia during exercise testing in men with stable angina. It is key to avoid concomitant administration of nitrates with any of the PDE5 inhibitors, because this combination can cause increased vasodilation and a subsequent drop in blood pressure. Sildenafil has an alpha-blocker precaution; tadalafil is contraindicated with alpha blockers except for 0.4 mg tamsulosin; vardenafil is contraindicated with alpha blockers.