Why are nitrates contraindicated with sildenafil (Viagra)?

Nitrates and sildenafil (Viagra) are both vasodilators, meaning they cause blood vessels to widen. When taken together, their combined effects can lead to significantly reduced blood pressure, resulting in severe hypotension. This occurs because nitrates dilate blood vessels and lower blood pressure by increasing blood flow, while sildenafil enhances the effect of nitric oxide, also promoting vasodilation. The synergistic effect of these two classes of medications can lead to dangerous drops in blood pressure, potentially causing dizziness, fainting, or even more serious cardiovascular complications. Consequently, patients are strongly advised against taking these two medications simultaneously to prevent such adverse effects.