Sildenafil: clinical use

Prescribing considerations

• Establish the indication and avoid duplication between ED and PAH sildenafil products or other PDE5 inhibitors.
• Before ED treatment, assess cardiovascular fitness for sexual activity and consider underlying causes and cardiovascular risk factors.
• PAH initiation and monitoring should be undertaken by an experienced specialist; review unexplained deterioration promptly.
• Consider increased susceptibility to vasodilation in hypotension, fluid depletion, left-ventricular outflow obstruction or autonomic dysfunction.
• Use caution with bleeding disorders, active peptic ulceration, penile deformity or conditions predisposing to priapism.
• The intravenous product is restricted to clinically and haemodynamically stable adults temporarily unable to take oral Revatio.

Contraindications and cautions

• Hypersensitivity to sildenafil or product excipients.
• Concurrent nitrates, nitric-oxide donors or riociguat.
• Sexual activity being inadvisable because of severe cardiovascular disease for ED products.
• Severe hypotension, severe hepatic impairment, recent myocardial infarction or stroke as specified by the individual product.
• Previous vision loss from non-arteritic anterior ischaemic optic neuropathy.
• Potent CYP3A4 inhibitors are contraindicated with selected PAH and pharmacy sildenafil products; check the exact product information.
• PAH secondary to sickle-cell anaemia is unsuitable for Revatio because of increased vaso-occlusive crises.

Monitoring

• Blood pressure and symptoms of postural hypotension where clinically relevant.
• Cardiovascular status and underlying disease in erectile dysfunction.
• PAH symptoms, functional status and clinical deterioration.
• New visual or hearing symptoms and prolonged erections.
• Tolerance and interaction risk after changes to CYP3A4 inhibitors or inducers.
• Monitor closely during PAH withdrawal because abrupt changes may cause clinical deterioration.

Clinical pharmacology

Sildenafil selectively inhibits PDE5, increasing cGMP-mediated smooth-muscle relaxation. It is metabolised mainly by CYP3A4 and, to a lesser extent, CYP2C9; its active N-desmethyl metabolite contributes to the clinical effect.

Formulation and product differences

• Selected erectile-dysfunction products are film-coated oral tablets; excipients vary between manufacturers, including lactose in some products.
• The PAH oral suspension is grape flavoured, contains sorbitol and sodium benzoate, requires reconstitution and must be shaken before measurement with its supplied syringe.
• The intravenous PAH solution is a clear, colourless hospital formulation for temporary replacement of oral therapy and does not require dilution or reconstitution.
• The oral suspension is licensed for specified adults and children; the selected injectable product is for adults only.

Oral suspension

Route: Oral

Strengths: 10 mg/mL

Tablet

Route: Oral

Strengths: 20 mg, 25 mg, 50 mg, 100 mg