What is the appropriate dosing for Sildenafil (Viagra)?

From the Guidelines

Viagra (sildenafil) should be prescribed at a starting dose of 50mg taken approximately one hour before sexual activity, with adjustments made based on effectiveness and tolerability, as recommended by the most recent guidelines 1. The dose can range from 25mg to 100mg, taken no more than once daily.

Key Considerations

• For older adults (over 65), those with liver or kidney impairment, or patients taking certain medications like protease inhibitors, a lower starting dose of 25mg is recommended.
• Viagra works by enhancing blood flow to the penis by inhibiting phosphodiesterase type 5 (PDE5), which normally breaks down cGMP, a chemical that relaxes smooth muscles in blood vessels.
• The medication should be taken on an empty stomach for optimal absorption, as high-fat meals can delay its effectiveness.
• Patients should be aware that sexual stimulation is still necessary for Viagra to work, as it does not automatically cause an erection.

Important Warnings

• Side effects may include headache, flushing, indigestion, and nasal congestion.
• Viagra should not be used by individuals taking nitrates for heart conditions as this combination can cause dangerous drops in blood pressure, and patients on sildenafil or vardenafil should avoid taking nitroglycerine for at least 24 hours, and 48 hours for tadalafil 1.

Clinical Guidance

• The American Heart Association and American College of Cardiology guidelines recommend that phosphodiesterase type 5 inhibitors should not be used concomitantly with nitrate medications, often used to treat chronic coronary disease, because of the potential for severe hypotension 1.
• The decision to use a phosphodiesterase type 5 inhibitor in patients on long-acting nitrate therapy should be guided by the need for continued nitrate therapy versus other alternative options available to the treating clinician 1.

From the FDA Drug Label

The recommended dose of sildenafil tablets is 20 mg three times a day (TID). Administer sildenafil tablet doses 4-6 hours apart. Take sildenafil tablet 3 times a day about 4 to 6 hours apart. Take sildenafil tablets at the same times every day.

The recommended dose of sildenafil is 20 mg taken three times a day, with doses 4-6 hours apart. It is essential to take sildenafil tablets at the same times every day. 2 2

From the Research

Viagra Dosing

• The recommended starting dose for men with erectile dysfunction (ED) is sildenafil 50 mg, however, most men are later titrated to sildenafil 100 mg for improved efficacy 3.
• A study found that sildenafil at 50 mg or 100 mg significantly improved erection quality, treatment satisfaction, anxiety levels, and the sexual experience compared with placebo during a double-blind, placebo-controlled trial 3.
• Improvements in patient-reported outcomes from baseline were statistically significant for both sildenafil 50 and 100 mg compared with placebo, with 56% of men on the 100-mg dose feeling no anxiety about the next intercourse attempt compared with 39% in the 50-mg group 3.

Efficacy and Safety

• Sildenafil has been shown to be effective in men with ED associated with diabetes and prostate cancer, and in psychogenic ED 4.
• The most commonly reported adverse effects with sildenafil are headache, flushing, and dyspepsia 4.
• Sildenafil is safe in men with coronary artery disease, provided it is not used with nitrates (a contraindication) 4, 5.
• A study found that sildenafil is an effective and well-tolerated treatment for ED regardless of patient age, including men at least 75 years old 6.

Comparison with Other Phosphodiesterase Inhibitors

• Vardenafil and tadalafil have been shown to be similarly effective to sildenafil in the treatment of ED, with similar adverse effects profiles 4, 7.
• Tadalafil has a longer duration of action than sildenafil and vardenafil, and may be preferred by some men due to its longer duration of action 4, 7.
• All three phosphodiesterase inhibitors (sildenafil, vardenafil, and tadalafil) must be used with caution in patients taking alpha(1)-adrenoceptors antagonists for benign prostatic hyperplasia 5, 7.