Tadalafil Tablets

Mechanism

Tadalafil inhibits PDE5 enzyme, preventing breakdown of cyclic GMP. Increased cGMP leads to smooth muscle relaxation, vasodilation, and improved blood flow in penile tissue, prostate, and pulmonary vasculature.

Pharmacokinetics

• Absorption: Rapidly absorbed; oral bioavailability ~80%; peak plasma concentration in ~2 hours; unaffected by food.
• Distribution: Volume of distribution ~63 L; plasma protein binding ~94%; widely distributed in vascular tissues.
• Metabolism: Extensively metabolized in liver via CYP3A4 to inactive metabolites; minor contribution from CYP2C9.
• Excretion: ~61% excreted in feces, ~36% in urine; negligible unchanged drug in urine.
• Half-life: ~17.5 hours, supporting once-daily dosing; therapeutic effect may last up to 36 hours.
• Special Populations: Clearance reduced in hepatic and renal impairment; dose adjustment required. Elderly patients may have increased exposure.
• Onset of Action: Clinical effect observed within 30–60 minutes after administration.

Side Effects

• Headache
• Flushing
• Nasal congestion
• Dyspepsia
• Dizziness
• Rare: priapism, visual disturbances

Contraindication

• Concomitant use with nitrates
• Severe cardiovascular disorders
• Hypersensitivity to tadalafil

Interaction

• Nitrates (risk of severe hypotension)
• Alpha-blockers (additive hypotensive effect)
• CYP3A4 inhibitors (ketoconazole, ritonavir – increase tadalafil levels)
• Alcohol (enhanced hypotensive effect)

Warning and Precautions

• Use under medical supervision only
• Monitor cardiovascular status before prescribing
• Caution in patients with hepatic or renal impairment

Dosage

As directed by the Physician.