Sildenafil for Erectile Dysfunction: Dosing and Management
Starting Dose and Administration
Begin with sildenafil 50 mg taken approximately 1 hour before sexual activity, not more than once daily. 1
- The FDA-approved starting dose is 50 mg for most men with erectile dysfunction 1
- Take on an empty stomach for optimal efficacy, as food (especially large meals) reduces absorption and effectiveness 1
- Sexual stimulation is absolutely necessary for sildenafil to work—this is a critical patient education point that accounts for many apparent treatment failures 1, 2
Dose Titration Strategy
Titrate to 100 mg if inadequate response after at least 5 separate attempts at the starting dose. 1, 3
- Sildenafil demonstrates dose-dependent efficacy: improvement increases from 25 mg to 50 mg to 100 mg 3
- The maximum dose is 100 mg once daily 1
- Reduce to 25 mg in patients with hepatic or renal impairment, elderly patients, or those taking CYP3A4 inhibitors (ritonavir, ketoconazole, erythromycin, cimetidine) 4
- Avoid use entirely in severe hepatic or renal disease 1
Efficacy Data
- Clinical trials show 69% successful intercourse attempts with sildenafil versus 35.5% with placebo 1
- Treatment response rates: 77% in men without comorbidities, 71% with cardiovascular disease/hypertension, 63% with diabetes, and 78% with depression 5
- Men with diabetes and post-prostatectomy patients have more severe ED at baseline and respond less robustly, often requiring the maximum 100 mg dose 1, 3
Absolute Contraindications and Critical Safety
Sildenafil is absolutely contraindicated with any form of nitrate medication due to risk of life-threatening hypotension. 1
- Explicitly ask about all forms of nitrate use before prescribing, including sublingual nitroglycerin, isosorbide mononitrate/dinitrate, and recreational "poppers" (amyl nitrite) 1
- If emergency nitrate administration is required, wait 24 hours after the last sildenafil dose before giving nitrates, under close medical supervision 2, 6
Cardiovascular Risk Stratification
Most ED patients can safely receive sildenafil, including those with asymptomatic coronary artery disease (<3 risk factors), controlled hypertension, mild stable angina, successful coronary revascularization, uncomplicated past MI, mild valvular disease, and CHF (NYHA class I). 1, 3
- Refer patients to cardiology before prescribing if they cannot perform moderate physical activity or have indeterminate cardiovascular risk 1, 6
- Serious adverse events occur in <2% of patients, with no significant difference from placebo 3
Common Adverse Effects
- Headache, flushing, dyspepsia, nasal congestion, and abnormal vision are the most frequent side effects 1, 4
- These are typically transient and mild to moderate in severity 4
- Adverse events follow a dose-response pattern but rarely require discontinuation 2
Optimizing Treatment Response Before Declaring Failure
Before switching therapies, ensure the trial was adequate by addressing modifiable factors. 2, 6
- Verify at least 5 separate attempts at maximum dose (100 mg) 1, 3
- Check for hormonal abnormalities, particularly testosterone deficiency (total testosterone <300 ng/dL)—combining sildenafil with testosterone therapy in hypogonadal men is more effective than sildenafil alone 2, 3
- Assess timing of dosing (1 hour before activity, on empty stomach) 1
- Confirm adequate sexual stimulation is occurring 1, 2
- Evaluate heavy alcohol use, which impairs response 2
- Address relationship issues with partner that may be contributing 2
Special Populations Requiring Dose Adjustment
- Hepatic/renal impairment: Start with 25 mg 1
- Elderly patients: Consider starting with 25 mg 4
- CYP3A4 inhibitor use: Start with 25 mg 4
- Diabetes or post-prostatectomy: Often require 100 mg due to more severe baseline ED 1, 3