Understanding Sildenafil: BNF Dosage Guidelines
What is Sildenafil According to BNF?
The British National Formulary (BNF) classifies sildenafil as a phosphodiesterase type-5 inhibitor, primarily prescribed for erectile dysfunction in adult men. Originally developed by Pfizer as Viagra, generic sildenafil contains the same active ingredient at a lower cost. Both options work identically by increasing blood flow to the penis during sexual arousal.
BNF Recommended Starting Dosage
According to BNF guidelines, the standard starting dose for sildenafil is 50mg, taken approximately one hour before sexual activity. The dose may be adjusted based on effectiveness and tolerability - reduced to 25mg for those experiencing side effects, or increased to 100mg if the initial dose proves insufficient. The maximum frequency is once daily, with at least 24 hours between doses.
How Sildenafil Works
Sildenafil blocks the phosphodiesterase type-5 enzyme, which normally breaks down cyclic guanosine monophosphate (cGMP). By inhibiting this enzyme, sildenafil allows blood vessels in the penis to remain relaxed longer, facilitating increased blood flow when sexually stimulated. It's crucial to understand that sexual arousal is still required - sildenafil doesn't create spontaneous erections.
Timeline and Duration
Most men notice effects within 30-60 minutes of taking sildenafil. The medication reaches peak concentration in the bloodstream after approximately one hour. Effects typically last 4-6 hours, though this doesn't mean erections persist for this duration. Food, particularly high-fat meals, can delay absorption and onset of action.
BNF Safety Considerations
The BNF outlines several important contraindications for sildenafil use. Men taking nitrate medications (such as GTN spray) should never use sildenafil due to potentially dangerous blood pressure drops. Those with severe cardiovascular disease, recent heart attacks or strokes, or severe liver impairment require careful medical assessment before starting treatment.
Common Side Effects
BNF documentation includes common side effects such as headaches, facial flushing, indigestion, and nasal congestion. These typically resolve within a few hours. Less common but more serious side effects include sudden vision or hearing loss, which require immediate medical attention. Most side effects are mild and temporary.
Drug Interactions
Sildenafil can interact with various medications. Alpha-blockers for prostate problems may cause additional blood pressure lowering when combined with sildenafil. Certain antibiotics and antifungal medications can increase sildenafil levels in the blood. Always inform your prescriber about all current medications during consultation.
Choosing Between Branded and Generic
At EverydayMeds, patients can choose between branded Viagra and generic sildenafil during checkout. Both contain identical active ingredients and work in the same way. Generic sildenafil offers significant cost savings whilst maintaining the same efficacy and safety profile as the branded version.
