Absorption: 15% absorbed following oral administration; absorption is rapid.
Distribution: Extensive tissue distribution; penetrates semen.
Protein Binding: 95%.
Metabolism/Excretion: Mostly metabolized by the liver (mainly CYP3A4 enzyme system, minor metabolism by CYP2C). M1 metabolite has anti-erectile dysfunction activity. Parent drug and metabolites are mostly excreted in feces. 2–6% renally eliminated.
Half-life: 4–6 hr.
Derm: flushing.
EENT: HEARING LOSS, VISION LOSS, rhinitis, sinusitis.
GI: dyspepsia, nausea.
GU: priapism.
Neuro: headache, amnesia, dizziness.
Misc: flu syndrome.
The tablets and orally disintegrating tablets are not interchangeable; the orally disintegrating tablets provide a higher level of systemic exposure compared to the tablets
Tablets
- PO (Adults): 10 mg taken 1 hr prior to sexual activity (range 5–20 mg; not to exceed one dose/24 hr); Concurrent use of ritonavir — single dose should not exceed 2.5 mg in any 72-hr period; Concurrent use of indinavir, saquinavir, atazanavir, clarithromycin, ketoconazole 400 mg daily, or itraconazole 400 mg daily — single dose should not exceed 2.5 mg/24 hr; Concurrent use of ketoconazole 200 mg daily, itraconazole 200 mg daily, or erythromycin — single dose should not exceed 5 mg/24 hr; Concurrent use of stable alpha-blocker therapy (not on potent CYP3A4 inhibitor) — 5 mg initial dose; titrate as tolerated; Concurrent use of stable alpha-blocker and potent CYP3A4 inhibitor therapy — 2.5 mg initial dose; titrate as tolerated.
- PO (Geriatric Patients
65 yr): 5 mg initial dose; titrate as tolerated.
Hepatic Impairment
- PO (Adults): Moderate hepatic impairment (Child-Pugh B) — May start with 5 mg dose (not to exceed 10 mg).
Orally Disintegrating Tablets
- PO (Adults): 10 mg taken 1 hr prior to sexual activity (not to exceed one dose/24 hr).
Therapeutic Classification: erectile dysfunction agents
Pharmacologic Classification: phosphodiesterase type 5 inhibitors
