Do Not Add Vardenafil to Tadalafil 5 mg Daily
You should not prescribe vardenafil on top of tadalafil 5 mg once daily—this combination is not supported by evidence and creates unnecessary risk without proven benefit. 1, 2
Why Combining PDE5 Inhibitors Is Not Recommended
There is no evidence supporting the concurrent use of two different PDE5 inhibitors. 1 The American Urological Association guidelines explicitly state that PDE5 inhibitors should be used as monotherapy, and clinical trials have never evaluated the safety or efficacy of combining different PDE5 inhibitors. 1
- All three PDE5 inhibitors (sildenafil, tadalafil, vardenafil) have similar efficacy and adverse event profiles, with no superiority of one agent over another. 1
- Combining PDE5 inhibitors would increase the risk of adverse effects (headache, flushing, hypotension, dyspepsia) without evidence of improved erectile function. 1
- Studies comparing PDE5 inhibitors plus non-PDE5 inhibitors versus PDE5 inhibitors alone showed increased adverse events with combination therapy. 1
The Correct Approach: Switch, Don't Stack
If tadalafil 5 mg daily is inadequate, you should switch to a different PDE5 inhibitor rather than adding one. 1, 2
Before switching, ensure the current trial is adequate:
- Verify the patient has taken tadalafil for at least 4-8 doses (adequate trial duration). 1
- Confirm proper timing and sexual stimulation are occurring. 1
- Rule out modifiable factors: hormonal abnormalities, heavy alcohol use, relationship issues, inadequate sexual stimulation. 1
- Ensure the patient understands that daily tadalafil provides continuous coverage and doesn't require timing with sexual activity. 3
If switching from tadalafil to vardenafil:
- No mandatory waiting period is required when switching between PDE5 inhibitors. 2
- Simply discontinue tadalafil and start vardenafil at the appropriate dose (typically 10 mg, taken 1 hour before sexual activity). 2, 4
- Vardenafil has a shorter duration of action (4-5 hours) compared to tadalafil (up to 36 hours), which some patients may prefer or find less effective. 2, 5, 4
Critical Safety Consideration: Nitrate Interaction
The primary concern with any PDE5 inhibitor regimen is the absolute contraindication with nitrates. 1, 2, 6
Timing requirements if nitrates become necessary:
- After tadalafil use: wait at least 48 hours before administering any nitrate. 1, 2, 6
- After vardenafil use: wait at least 24 hours before administering nitrates. 1, 2
- The combination of PDE5 inhibitors with nitrates can cause profound hypotension, myocardial infarction, and death. 1, 2, 6
Documentation is critical:
- Always document which PDE5 inhibitor the patient is taking and when it was last taken, particularly important for emergency situations where nitrates might be needed. 2, 6
- Counsel the patient that if they develop chest pain requiring emergency care, they must inform providers about their PDE5 inhibitor use. 6
Common Pitfall to Avoid
Do not assume that because the patient is on a low daily dose of tadalafil (5 mg), adding vardenafil "as needed" would be safe or effective. This approach: