Additional Information

Description
Sildenafil Tablets, USP contain sildenafil citrate, a phosphodiesterase type 5 (PDE5) inhibitor. Sildenafil citrate is chemically designated as 1-[[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-4-ethoxyphenyl]sulfonyl]-4-methylpiperazine citrate. Its molecular formula is C22H30N6O4S·C6H8O7, with a molecular weight of 666.7 g/mol. Each blue, film-coated, diamond-shaped tablet contains 50 mg of sildenafil (equivalent to 68.85 mg sildenafil citrate) for oral administration.

Sildenafil is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). By inhibiting PDE5 in the corpus cavernosum, sildenafil increases cGMP levels, enhancing nitric oxide (NO)-mediated smooth muscle relaxation and blood flow during sexual stimulation.

Indications and Usage
Treatment of erectile dysfunction (ED).

Important Safety Information
Contraindications: Concomitant use with nitrates (e.g., nitroglycerin) or guanylate cyclase stimulators (e.g., riociguat). Hypersensitivity to sildenafil or any tablet component.

Warnings and Precautions

• Cardiovascular Risk: Not recommended for patients with unstable angina, recent stroke, or life-threatening arrhythmia. Evaluate cardiovascular status before prescribing.
• Priapism: Seek emergency care if erection persists >4 hours.
• Vision Loss: Non-arteritic anterior ischemic optic neuropathy (NAION) reported. Discontinue use if sudden vision loss occurs.
• Hearing Loss: Sudden decreases in hearing reported. Discontinue if symptoms occur.
• Hypotension: Avoid concomitant use with alpha-blockers (risk of severe hypotension).
• Renal/Hepatic Impairment: Reduce dose to 25 mg in severe impairment.

Adverse Reactions 
Headache (16%), flushing (10%), dyspepsia (7%), nasal congestion (4%), visual disturbances (3%), dizziness (2%).

Drug Interactions

• Nitrates: Absolute contraindication (severe hypotension).
• CYP3A4 Inhibitors (e.g., ketoconazole): Reduce sildenafil dose to 25 mg.
• Alpha-Blockers: Separate dosing by =4 hours.

Dosage and Administration

• Recommended dose: 50 mg taken 30–60 minutes before sexual activity (range: 25–100 mg once daily).
• Maximum dosing frequency: Once per 24 hours.
• Adjust to 25 mg in hepatic/severe renal impairment or with CYP3A4 inhibitors.

Patient Counseling

• Review Medication Guide.
• Avoid nitrates, grapefruit juice, and alcohol.
• Report erections >4 hours, vision/hearing changes, or chest pain.