Trade Names: Viagra, Revatio
Drug Class: Phosphodiesterase 5 (PDE5) inhibitor
Preparations: Revatio 20 mg, Viagra 25-, 50-, 100 mg tablets
Dose: For pulmonary hypertension 20 mg three times daily; for erectile dysfunction 50 mg 1 hour before sex
Indications: Erectile dysfuntion (Viagra), pulmonary arterial hypertension (Revatio), sildenafil also tried in Raynaud’s and for digital ulcers associated with scleroderma
Mechanism of Action: Inhibits PDE5 and thus increases cyclic GMP concentrations causing vasodilation
Contraindications: Hypersensitivity, concurrent use of any form of nitrates, including ointment
Precautions: Potential for drug interactions; not recommended for children with pulmonary hypertension (increased mortality)
Pregnancy Risk: B
Adverse Effects
Common: Flushing, headache, dyspepsia, dizziness
Less common: Visual disturbance including color changes, allergy, rash, hearing loss, hypotension (particularly with nitrates or cytochrome P450 (CYP)3A inhibitors), priapism
Drug Interactions
CYP3A inhibitors (strong inhibitors include clarithromycin,telithromycin, ketoconazole, itraconazole, nefazodone and many HIV drugs; moderate inhibitors include aprepitant, diltiazem, verapamil, erythromycin, fluconazole, posaconazole, voriconazole, grapefruit juice): Increased sildenafil concentrations.
Nitrates: Hypotension; avoid this combination
Alpha-1 blockers: Increased risk of hypotension
Patient Instructions: Avoid grapefruit juice; stop drug if have sudden visual or hearing loss
Comments: Small studies or case-series suggest PDE5 inhibitors are modestly effective for Raynaud’s and digital ulcers associated with scleroderma.
Clinical Pharmacology: Onset 60 minutes, duration 2-4 hours, half-life 4 h. Metabolized by CYP3A4.
Adapted from: RheumaKnowledgy