Interactions between cialis(tadalafil) and Alfuzosin (alfuzosin)
alfuzosin and tadalafil (Moderate Drug-Drug)
ADJUST DOSE: Tadalafil may potentiate the hypotensive effect of alpha blockers, resulting in symptomatic hypotension in some patients. Tadalafil inhibits phosphodiesterase-5-mediated degradation of cyclic guanosine monophosphate (cGMP), which in vascular smooth muscles can cause peripheral vasodilation that may be additive with that induced by alpha blockers. In 18 healthy subjects taking doxazosin 8 mg daily for at least 7 days, administration of tadalafil 20 mg resulted in significant augmentation of the blood pressure lowering effect of doxazosin, an alpha-1 adrenergic blocker. Specifically, nine patients given tadalafil had either a standing systolic blood pressure of less than 85 mm Hg or a decrease from baseline of greater than 30 mm Hg at one or more time points, compared to three such patients when given placebo. Two significant adverse events (vertigo and dizziness) potentially related to blood pressure effects were reported with tadalafil, compared to none with placebo. No syncope was reported. In contrast, no significant adverse events related to decreases in blood pressure were observed when a single dose of tadalafil 10 mg or 20 mg was administered to healthy subjects taking 0.4 mg once-daily tamsulosin, a selective alpha-1A adrenergic blocker.
MANAGEMENT: Caution is advised if tadalafil is used in combination with alpha blockers. Patients who demonstrate hemodynamic instability on alpha blocker therapy alone are at increased risk of symptomatic hypotension with concomitant use of tadalafil. Therefore, patients should be stable on alpha blocker therapy prior to initiating tadalafil, and tadalafil should be initiated at the lowest recommended dosage. In those patients already on an optimized dosage of tadalafil, alpha blocker therapy should be initiated at the lowest dosage. The safety of tadalafil in combination with alpha blockers may be affected by other variables such as intravascular volume depletion and use of other antihypertensive medications.
