Key Takeaway
All PDE5 inhibitors share a similar overall safety profile. The differences are in which side effects are more common with each drug. Tadalafil causes more back pain but less flushing. Sildenafil causes more visual changes. Avanafil may have the mildest overall profile but is the least studied and most expensive.
The Complete Side Effect Comparison
| Side Effect | Sildenafil | Tadalafil | Vardenafil | Avanafil |
|---|---|---|---|---|
| Headache | 16% | 11% | 15% | 9% |
| Flushing | 10%+ | 3–5% | 10%+ | 4% |
| Nasal congestion | Common | Common | Common | Less common |
| Back pain | Rare | 6–8% | Rare | Rare |
| Muscle aches | Rare | 5–7% | Rare | Rare |
| Acid reflux | 5% | 8% | Similar | Lower |
| Visual changes | Yes (PDE6) | Rare | Yes (PDE6) | Rare |
| Overall AE rate | 35% | 34% | 47% | ~25%* |
*Avanafil data from smaller study populations. Sildenafil/tadalafil/vardenafil rates from a 130,000-patient study.1
Understanding Why Side Effects Differ
All four medications inhibit PDE5, but each has different selectivity for related PDE enzymes found elsewhere in the body. This selectivity profile explains most of the side effect differences:
- PDE6 (retina): Sildenafil and vardenafil inhibit PDE6, causing blue-tinted vision and light sensitivity. Tadalafil and avanafil are more selective for PDE5 and largely spare PDE6.
- PDE11 (muscle/skeletal): Tadalafil has some activity against PDE11, which likely explains the back pain and muscle aches unique to tadalafil.
- Half-life: Tadalafil's 17.5-hour half-life means side effects, when they occur, can last longer than with the shorter-acting drugs.
Choosing Based on Side Effects
If flushing is your concern: choose tadalafil
Tadalafil has the lowest rate of facial flushing among the major PDE5 inhibitors.1
If visual changes worry you: choose tadalafil or avanafil
Both largely spare PDE6, making blue-tinted vision extremely rare.
If you want to avoid back pain: choose sildenafil, vardenafil, or avanafil
Back pain and muscle aches are primarily a tadalafil issue.
If you want the mildest overall profile: consider avanafil
Avanafil (Stendra) is the newest PDE5 inhibitor and appears to have the lowest overall adverse event rates. The catch: it's significantly more expensive (no widely available generic yet) and has the smallest body of long-term safety data.4
Serious Side Effects: Rare but Real
Across nearly two decades and hundreds of millions of prescriptions, PDE5 inhibitors have an excellent cardiovascular safety record.2 However, rare serious events can occur:
- Priapism (erection lasting 4+ hours): rare but requires emergency treatment
- Sudden hearing loss: extremely rare, reported with all PDE5 inhibitors
- Non-arteritic anterior ischemic optic neuropathy (NAION): extremely rare sudden vision loss
- Severe hypotension: primarily when combined with nitrates (contraindicated)
If you experience a prolonged erection, sudden vision loss, or sudden hearing loss, seek emergency medical attention immediately.
Discuss Side Effects With a Provider
A licensed telehealth provider can help you choose the medication with the best side effect profile for your situation.
Get Evaluated →The Bottom Line
No PDE5 inhibitor is side-effect-free, but all are well-tolerated by the majority of men. The differences between them are real but generally mild. If one medication's side effects bother you, switching to another often resolves the issue. The goal is to find the medication where you get the best efficacy with the most tolerable side effect profile for your body.