Switching Between Tadalafil and Vardenafil
You can switch immediately between tadalafil and vardenafil without any mandatory waiting period—no washout is required for safety when transitioning between these PDE5 inhibitors. 1
Why Immediate Switching Is Safe
The confusion likely stems from mixing up two completely different clinical scenarios:
- Switching between PDE5 inhibitors (tadalafil ↔ vardenafil): No waiting period needed 1
- Using nitrates after taking a PDE5 inhibitor: Mandatory waiting periods apply (48 hours for tadalafil, 24 hours for vardenafil) 1, 2
The Critical Distinction
Between PDE5 Inhibitors (Safe to Switch Immediately)
- The American Urological Association guidelines explicitly recommend trying a different PDE5 inhibitor if the first one is ineffective or poorly tolerated 1
- No evidence supports superiority of one PDE5 inhibitor over another, making switching a reasonable clinical strategy 1
- All three agents (sildenafil, vardenafil, tadalafil) have similar efficacy profiles in treating erectile dysfunction 3, 4
Between PDE5 Inhibitors and Nitrates (Dangerous—Requires Waiting)
- After tadalafil use, you must wait at least 48 hours before administering any nitrate therapy due to tadalafil's 17.5-hour half-life 1, 5, 2
- After vardenafil use, you must wait at least 24 hours before administering nitrates 1, 2
- The combination of PDE5 inhibitors with nitrates causes profound hypotension, myocardial infarction, and potentially death 1, 5
Clinical Approach to Switching
When switching from tadalafil to vardenafil or vice versa:
- Ensure adequate trial of the first agent before switching (typically 4-6 attempts at optimal dosing) 1
- Start the new PDE5 inhibitor at standard dosing without any washout period 1
- Document which medication the patient is currently taking for emergency situations where nitrate administration might be needed 1
Key pharmacokinetic differences to counsel patients about:
- Tadalafil provides effects lasting up to 36 hours with a half-life of 17.5 hours 1, 6
- Vardenafil has a shorter duration of action lasting approximately 4-5 hours 1
- These differences affect timing of sexual activity but not safety of switching between them 4, 7
Common Pitfall to Avoid
The most dangerous error is confusing the nitrate contraindication waiting periods with switching between PDE5 inhibitors. Always verify that patients are not taking nitrates before prescribing any PDE5 inhibitor, regardless of which one they previously used 1, 6.