Both are FDA-approved oral medications for erectile dysfunction in the same drug class. But their differences in duration, dosing options, and lifestyle fit are meaningful. Here’s the physician’s guide.
By Dr. Teja V. Surapaneni, MD, MS • Board-Certified Internal Medicine (ABIM) • Licensed NV, WA, OR, WI • May 2026
Both tadalafil and sildenafil are PDE5 inhibitors. They work by blocking the enzyme phosphodiesterase type 5, which normally breaks down cGMP in the smooth muscle cells of penile blood vessels. When cGMP builds up, blood vessels relax and widen, allowing increased blood flow that facilitates an erection in response to sexual stimulation. Neither medication produces an erection without arousal — they improve the body’s natural response.
| Feature | Sildenafil | Tadalafil |
|---|---|---|
| Duration of action | 4–6 hours | Up to 36 hours (as-needed); continuous (daily) |
| Dosing options | As-needed only (25, 50, 100 mg) | As-needed (10, 20 mg) or daily (2.5, 5 mg) |
| Onset after dose | 30–60 minutes | 30–45 minutes (may be slower in some) |
| Food interaction | High-fat meals delay absorption | Not significantly affected by food |
| BPH (enlarged prostate) | Not indicated | FDA-approved for both ED + BPH |
| Back/muscle aches | Rare | Possible with as-needed dosing |
Sildenafil is typically active for 4–6 hours after taking a dose. Tadalafil has a much longer half-life — approximately 17.5 hours — so the as-needed version (10 or 20 mg) remains active for up to 36 hours. Daily tadalafil 5 mg maintains steady-state levels continuously, eliminating any need to time the medication around sexual activity.
Sildenafil’s absorption is reduced by high-fat meals — taking it after a heavy dinner can delay or diminish its effectiveness. Tadalafil is not significantly affected by food. For men who prefer not to plan meals around medication, tadalafil offers a practical advantage.
Daily tadalafil 5 mg is generally preferred for men who:
As-needed sildenafil or as-needed tadalafil are reasonable for men who prefer to take medication only when needed or have infrequent sexual activity. Some men prefer sildenafil for its lower cost; others prefer the 36-hour flexibility of as-needed tadalafil.
Both medications share a similar side effect profile: headache, facial flushing, nasal congestion, and mild visual disturbances (particularly sildenafil at higher doses). These are dose-dependent and usually mild. Because sildenafil has a shorter duration, side effects resolve more quickly. Tadalafil’s unique potential side effect is back pain or muscle aches, which occurs in some patients due to activity on PDE11 in muscle tissue — typically resolving within 24–48 hours.
PDE5 inhibitors must never be taken with nitrate medications (such as nitroglycerin, or “poppers”) or riociguat, due to the risk of severe hypotension. Use caution with alpha-blockers and certain cardiovascular conditions; your physician will confirm you are fit for sexual activity. Seek emergency care for chest pain or an erection lasting more than 4 hours, and stop and seek urgent care for sudden vision or hearing loss. Your YourMD physician will review your complete medication list and health history during consultation.
Our men’s health program starts with an evaluation by a board-certified MD, then a personalized prescription and ongoing messaging for dose questions. FDA-approved sildenafil or daily tadalafil tablets are $59/month. A compounded sublingual sildenafil troche ($89/month) is also available as an alternative dosage form; it is not FDA-approved, onset data for compounded troches are limited, and it is prepared by a licensed 503A compounding pharmacy (for example Hallandale Pharmacy or Valiant Compounding Pharmacy) named on your prescription label.
Medical disclaimer: This article is for educational purposes only and does not constitute medical advice. Consult a qualified physician before starting any prescription medication. Page medically reviewed by Teja V. Surapaneni, MD, MS — Board-Certified Internal Medicine (NV, WA, OR, WI). Last reviewed: May 2026.