Overview
A long-acting phosphodiesterase type 5 inhibitor approved for erectile dysfunction, benign prostatic hyperplasia, and pulmonary arterial hypertension.
How it works
Tadalafil belongs to a family of medicines that improve blood flow by relaxing the smooth muscle lining certain blood vessels. It works downstream of nitric oxide, a natural signaling molecule the body uses to widen blood vessels. By preventing the breakdown of a key messenger in that pathway, tadalafil keeps the relaxation signal switched on for longer.
This vessel-relaxing effect explains its different uses. In erectile dysfunction it improves penile blood flow in response to sexual stimulation; in benign prostatic hyperplasia it eases lower urinary tract symptoms; and in pulmonary arterial hypertension it lowers pressure in the lung's blood vessels. Its defining feature among these drugs is a notably long duration of action, which is why one of its branded forms can be taken once daily.
Tadalafil is FDA-approved for all three indications and is widely prescribed. A critical safety point is that it must not be combined with nitrate medications or certain other vasodilators, because the combination can cause dangerous drops in blood pressure. It interacts with several drugs metabolized through the liver and should be used under medical guidance.
Mechanism · Detailed Analysis
Molecular targetTadalafil is a selective, reversible inhibitor of phosphodiesterase type 5 (PDE5), the enzyme that hydrolyzes cyclic guanosine monophosphate (cGMP) in vascular and other smooth muscle. It has relatively high selectivity for PDE5 over most other PDE isoforms, though some cross-reactivity with PDE11 distinguishes it within the class.
Signaling & downstream effectsIn the nitric oxide-cGMP pathway, NO activates soluble guanylate cyclase to generate cGMP, which lowers intracellular calcium and relaxes smooth muscle. By blocking PDE5-mediated cGMP degradation, tadalafil potentiates and prolongs this relaxation, enhancing vasodilation in penile corpus cavernosum, prostatic and bladder neck tissue, and the pulmonary vasculature. The effect remains dependent on upstream NO release, so sexual stimulation is still required for erectile benefit.
PharmacokineticsTadalafil is orally bioavailable and notable for a long elimination half-life of roughly a day and a half, far longer than earlier agents in the class, which supports both on-demand and once-daily dosing. It is metabolized predominantly by hepatic CYP3A4, so strong CYP3A4 inhibitors and inducers meaningfully alter exposure.
CaveatsCo-administration with organic nitrates or guanylate cyclase stimulators is contraindicated due to additive, potentially severe hypotension; caution applies with alpha-blockers and other antihypertensives. Rare reported adverse events include sudden hearing loss and non-arteritic anterior ischemic optic neuropathy. Dose adjustment is needed in renal and hepatic impairment.
Published EvidenceLoading cited studies from PubMed…
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Educational aggregation of public literature. Not medical advice and not a recommendation to use any compound. Many compounds here are not approved for human use. Consult a licensed clinician.