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Viagra (sildenafil citrate)

In this drug monograph:

• Viagra (sildenafil) Indications
• Dosage and Administration of Viagra (sildenafil)
• Contraindications, Warnings, and Precautions
• Side Effects or Adverse Reactions
• Drug Interactions
• Efficacy of Viagra (sildenafil)
• Pharmacology (Mechanism of Action)
• Viagra Pill Identification and Imprint Code
• Viagra User Reviews

Viagra (sildenafil) Indications

Treatment of erectile dysfunction (ED)

Dosage and Administration of Viagra (sildenafil)

Viagra is a selective phosphodiesterase type 5 (PDE5) inhibitor available as 25, 50, and 100 mg tablets for oral administration.

• The recommended dose for most patients is 50 mg taken as needed about one hour before sexual activity. It may be taken between 30 minutes and four hours prior to sexual activity. Depending on effect and tolerability, the dose may be increased to a maximum dose of 100 mg daily or reduced to 25 mg daily. It should not be used more than once daily.
• Individuals older than 65 years, with liver failure or creatinine clearance <30 ml/min, or using potent cytochrome P450 inhibitors (for example, erythromycin, ketoconazole, itraconazole, and saquinavir [Invirase]) should start at 25 mg.
• Individuals taking ritonavir should not exceed 25 mg daily in any 48 hour period.

Contraindications, Warnings, and Precautions

Contraindications

• Use of nitrates (for example,, nitroglycerine, isosorbide): Viagra may increase hypotensive effects of nitrates.
• Hypersensitivity reactions to tadalafil (Viagra or Revatio)

Warnings and Precautions

• Angina: Patients with angina should not use Viagra because sexual activity may precipitate angina.
• Prolonged erections and priapism have been reported.
• Sudden loss of vision: NAION (non-arteritic anterior ischemic optic neuropathy).
• Sudden hearing loss has been reported.
• Alpha blockers and antihypertensives: Viagra potentiates the antihypertensive effects of alpha blockers and antihypertensives.
• Renal impairment: Clearance is reduced in patients with severe renal impairment (creatinine clearance <30 ml/min). See dosing section.
• Hepatic impairment: Main route of excretion is metabolism via CYP3A4 and CYP2C9 liver enzymes. See dosing section.
• CYP3A4 inhibitors (for example, ritonavir, ketoconazole, itraconazole, saquinavir, erythromycin): Limit dose (see dosage and administration).
• Other PDE5 inhibitors: Viagra should not be combined with other PDE5 inhibitors.
• Bleeding: PDE5 is found on platelets. Use of Viagra in patients with bleeding disorders or active peptic ulcers has not been evaluated.