Sildenafil is a phosphodiesterase type-5 inhibitors licensed for the treatment of erectile dysfunction; they are not recommended for use with other treatments for erectile dysfunction.

Indications: treatment of erectile dysfunction.

Cautions: hypotension (avoid if systolic blood pressure below 90 mmHg); intravascular volume depletion; left ventricular outflow obstruction; cardiovascular disease; autonomic dysfunction; pulmonary venoocclusive disease; anatomical deformation of the penis, predisposition to priapism; bleeding disorders or active peptic ulceration; consider gradual withdrawal; interactions should be used with caution in cardiovascular disease, left ventricular outflow obstruction, anatomical deformation of the penis (e.g. angulation, cavernosal fibrosis, Peyronie’s disease), and in those with a predisposition top riapism (e.g. in sickle-cell disease, multiple myeloma, or leukaemia). Concomitant treatment with aphosphodiesterase type-5 inhibitor and an alpha- blocker can increase the risk of postural hypotension— initiate treatment with a phosphodiesterasetype-5 inhibitor (at a low dose) only once the patient is stable on the alpha-blocker.

Note: not recommended for use with other treatments for erectile dysfunction. The patient should be assessed appropriately before prescribing sildenafil.

Contra-indications: recent history of stroke or myocardial infarction, history of non-arteritic anterior ischaemic optic neuropathy; hereditary degenerative retinal disorders; sickle-cell anaemia; avoid concomitant use of nitrates.

Hepatic impairment: for pulmonary hypertension, if usual dose not tolerated, reduce oral dose to 20mgtwice daily, or reduce intravenous dose to 10mg twice daily; manufacturer advises avoid in severe impairment.

Renal impairment: for pulmonary hypertension, if usual dose not tolerated, reduce oral dose to 20mg twice daily, or reduce intravenous dose to 10mg twice daily.

Pregnancy: use only if potential benefit outweighs risk—no evidence of harm in animal studies

Breast-feeding: manufacturer advises avoid - no information available

Side Effects: dyspepsia, nausea, vomiting, headache (including migraine), flushing, dizziness, myalgia, back pain, visual disturbances (non-arteritic anterior ischaemic optic neuropathy has been reported—stop drug if sudden visual impairment occurs), and nasal congestion. Less common side effects include painful red eyes, palpitation, tachycardia, hypotension, hypertension, epistaxis. Other side effects: reported rarely include syncope, hypersensitivity reactions (including rash, facial oedema, and Stevens-Johnson syndrome), and priapism. Serious cardiovascular events (including arrhythmia, unstable angina, and myocardial infarction), seizures, sudden hearing loss (discontinue drug and seek medical advice), and retinal vascular occlusion have also been reported.

Dose: ADULT over 18 years initially 50mg approx. 1 hour before sexual activity, subsequent doses adjusted according to response to 25–100mg as a single dose as needed; max. 1 dose in 24 hours (max. single dose100 mg) Onset of effect may be delayed if taken with food.