Sildenafil vs Tadalafil
FDA Approved vs FDA Approved
avoid Researched · 95% Do not combine PDE5 inhibitors. Additive pharmacological effect on cGMP accumulation increases risk of severe hypotension, priapism, and other adverse events with no additional therapeutic benefit.
Molecular Data
Sildenafil Tadalafil
Weight 474.58 Da 389.40 Da
Half-life ~3-5 hours ~17.5 hours
Type Small molecule phosphodiesterase type 5 (PDE5) inhibitor Small molecule phosphodiesterase type 5 (PDE5) inhibitor
Key Benefits
Sildenafil
01 First and most extensively studied PDE5 inhibitor with over 25 years of clinical data
02 Rapid onset of action (30-60 minutes) allows event-based dosing
03 FDA-approved for both erectile dysfunction (Viagra) and pulmonary arterial hypertension (Revatio)
04 Flexible dosing range (25-100mg) permits individualized titration
05 Shorter duration of action may be preferred by patients who want time-limited pharmacological effect
06 Extensive generic availability makes it one of the most affordable PDE5 inhibitors
07 Well-established safety profile across diverse patient populations
08 Proven efficacy in difficult-to-treat ED including diabetic and post-prostatectomy patients
Tadalafil
01 Long-acting duration with a 36-hour therapeutic window
02 Daily low-dose option (2.5-5mg) eliminates timing constraints
03 FDA-approved for both ED and BPH/LUTS
04 Minimal food interaction compared to other PDE5 inhibitors
05 Improved endothelial function and blood flow
06 Lower incidence of visual side effects vs. sildenafil
07 Potential benefits for exercise performance via enhanced blood flow
08 Well-established long-term safety profile
Dosing Protocols
Sildenafil
50mg as-needed (range 25-100mg) / As needed, max once per 24 hours
PAH (IV, when oral not feasible) 10mg (equivalent to 20mg oral) Three times daily as IV bolus
Tadalafil
5mg daily or 10-20mg as-needed / Once daily or as-needed (max once per 24 hours)
Side Effects
Sildenafil
Headache (16% incidence, most common side effect)
Flushing / warmth (10%, due to systemic vasodilation)
Dyspepsia / indigestion (7%)
Nasal congestion / rhinitis (4%)
Visual disturbances -- blue-tinged vision, increased brightness perception, blurred vision (3%, due to PDE6 cross-reactivity in retinal photoreceptors)
Dizziness (2%)
Diarrhea (3%)
Rash (2%)
Tadalafil
Headache (11-15% incidence, most common side effect)
Dyspepsia / indigestion (4-13%)
Back pain (3-9%, relatively unique to tadalafil among PDE5 inhibitors)
Myalgia / muscle aches (1-7%, thought to be related to PDE11 inhibition)
Nasal congestion / rhinitis (3-5%)
Flushing (1-4%)
Limb pain (1-3%)
Dizziness (1-2%)
Contraindications
Concurrent use of any organic nitrate medication (absolute contraindication)
Concurrent use of guanylate cyclase stimulators (e.g., riociguat)
Known hypersensitivity to sildenafil or any tablet excipient
Severe hepatic impairment (starting dose 25mg recommended in moderate impairment)
Severe renal impairment with CrCl <30 mL/min (starting dose 25mg recommended)
Recent stroke or myocardial infarction (within 6 months per original labeling)
Unstable angina or angina during sexual intercourse
Uncontrolled hypertension or symptomatic hypotension (resting BP <90/50 mmHg)
Hereditary degenerative retinal disorders including retinitis pigmentosa
History of NAION (relative contraindication -- increased recurrence risk)
Conditions predisposing to priapism (sickle cell anemia, multiple myeloma, leukemia)
Concurrent use of any organic nitrate medication (absolute contraindication)
Concurrent use of guanylate cyclase stimulators (e.g., riociguat)
Known hypersensitivity to tadalafil or any tablet excipient
Severe hepatic impairment (Child-Pugh Class C)
Recent stroke or myocardial infarction (within 90 days)
Unstable angina or angina during sexual intercourse
Uncontrolled hypertension (>170/100 mmHg) or hypotension (<90/50 mmHg)
NYHA Class IV heart failure
Hereditary degenerative retinal disorders (including retinitis pigmentosa)
History of NAION (relative contraindication -- increased recurrence risk)
Research Evidence
Sildenafil Tadalafil
Status FDA Approved FDA Approved
References 5 studies 5 studies
FDA Approved Yes Yes
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This comparison is for educational and research purposes only. Consult a healthcare professional before use.