Potentiated hypotensive effects of nitrates. Additive effect on BP w/ α-blockers (doxazosin, tamsulosin or alfuzosin). Small reductions in BP w/ amlodipine, angiotensin II receptor blockers, enalapril, & metoprolol. Increased potential for orthostatic signs & symptoms including increase in heart rate, decrease in standing BP, dizziness & headache w/ substantial consumption of alcohol (eg, ≥5 u). Reduced apparent rate of absorption w/o altering exposure (AUC) w/ antacids (Mg hydroxide/Al hydroxide). Increased exposure w/ CYP3A4 inhibitors (eg, ketoconazole, erythromycin, itraconazole, & grapefruit juice) & HIV PIs (eg, ritonavir). Reduced exposure w/ CYP3A4 inducers (eg, rifampicin, carbamazepine, phenytoin, & phenobarb).