Complete BNF Sildenafil Safety & Prescribing Guide
BNF Dosage Guidelines for Sildenafil
According to British National Formulary guidelines, sildenafil is available in 25mg, 50mg, and 100mg tablets. The standard starting dose is 50mg, taken approximately one hour before sexual activity. Dosage may be adjusted to 25mg if side effects occur, or increased to 100mg if 50mg proves insufficient. Both generic sildenafil and branded Viagra contain the same active ingredient - patients can choose either option during checkout based on preference and budget.
Critical Contraindications Checklist
The BNF clearly states that sildenafil must not be used by patients taking nitrate medications such as glyceryl trinitrate (GTN spray) or isosorbide mononitrate, as this combination can cause dangerous blood pressure drops. Other absolute contraindications include severe cardiovascular disease, recent heart attack or stroke (within 6 months), severe liver impairment, and hypotension. Patients with hereditary retinal disorders should also avoid sildenafil treatment.
Important Drug Interactions
Healthcare professionals must review all current medications before prescribing sildenafil. Alpha-blockers used for prostate problems can enhance hypotensive effects, requiring careful monitoring. CYP3A4 inhibitors like ritonavir and ketoconazole may increase sildenafil levels, necessitating dose reduction. Blood pressure medications may require adjustment, and patients should inform prescribers about all supplements and over-the-counter medicines.
Clinical Assessment Requirements
BNF guidelines emphasise that sildenafil requires proper clinical assessment by a UK-licensed prescriber. This includes cardiovascular risk evaluation, medication review, and assessment of underlying causes of erectile dysfunction. EverydayMeds ensures all consultations meet these standards, with patients able to choose between sildenafil (generic) or Viagra (branded) following successful assessment. The medication typically works within 30-60 minutes and effects may last 4-6 hours, though sexual stimulation remains necessary for effectiveness.
