No, Concurrent Use of Two PDE5 Inhibitors is Not Recommended
A 70-year-old man taking tadalafil 5 mg daily for BPH should not add vardenafil 20 mg, as combining two PDE5 inhibitors simultaneously is contraindicated due to increased risk of severe hypotension and other adverse effects. 1, 2
Why This Combination is Dangerous
Mechanism of Harm
- Both tadalafil and vardenafil are PDE5 inhibitors that work through the same mechanism—inhibiting phosphodiesterase type 5 to increase cyclic GMP levels 3
- Combining them creates additive vasodilatory effects, significantly increasing the risk of dangerous hypotension 2
- This is pharmacologically similar to the well-established contraindication of combining PDE5 inhibitors with nitrates, which can cause potentially fatal hypotension 2
Specific Safety Concerns in This Patient
- At 70 years old, this patient likely has age-related cardiovascular changes that increase vulnerability to hypotensive episodes 4
- The tadalafil 5 mg daily dosing means he has continuous drug levels (half-life allows for steady-state concentrations), making any additional PDE5 inhibitor particularly risky 2
- Common adverse events like headache, back pain, dyspepsia, and dizziness would be amplified with dual therapy 2, 5
If Erectile Dysfunction is the Concern
The Correct Approach
- If the patient needs treatment for erectile dysfunction in addition to his BPH therapy, the tadalafil dose should be optimized rather than adding a second PDE5 inhibitor 6, 2
- Tadalafil 5 mg daily treats both BPH and ED simultaneously—this is an FDA-approved indication 6, 7
- If 5 mg daily is insufficient for ED, consider increasing to tadalafil 5 mg daily with as-needed dosing adjustments, or switching to as-needed higher-dose tadalafil (10-20 mg) taken prior to sexual activity 2
Evidence for Single-Agent Optimization
- Studies demonstrate that tadalafil 5 mg daily significantly improves both IPSS scores (mean change -5.6 vs placebo -3.6) and erectile function in men with both conditions 7, 8
- Unlike sildenafil and vardenafil, tadalafil's efficacy for ED is not dose-dependent between 5-20 mg, though individual response varies 2
- An adequate trial consists of at least 5 separate attempts at maximum dose before declaring treatment failure 2
Clinical Pitfalls to Avoid
Common Errors
- Never combine two PDE5 inhibitors concurrently—this is not standard practice and lacks safety data 6, 2
- Do not assume that adding a different PDE5 inhibitor will provide additional benefit; the mechanism is identical across all agents 3
- Before switching or adjusting therapy, verify the patient is using the medication correctly (sexual stimulation required, proper timing, avoiding large meals) 1, 2
If Current Therapy is Inadequate
- Evaluate whether the trial was adequate: assess timing and frequency of dosing, adequacy of sexual stimulation, food or drug interactions, and relationship factors 2
- Consider switching to a different single PDE5 inhibitor (vardenafil or sildenafil) rather than combining agents 6
- For men with testosterone deficiency and ED, combining tadalafil with testosterone therapy may be more effective than tadalafil alone 2
Alternative Management Strategy
If BPH Symptoms Require Tadalafil but ED Needs Different Treatment
- Stop tadalafil and switch to vardenafil as-needed dosing if BPH symptoms are adequately controlled and ED is the primary concern 6
- Consider adding an alpha-blocker (like tamsulosin) for BPH while using as-needed vardenafil for ED, though note that combination of tadalafil with alpha-blockers offers no advantage over either alone 6
- Reassess whether BPH truly requires daily PDE5 inhibitor therapy, as alpha-blockers or 5-alpha reductase inhibitors may be more appropriate primary BPH treatments depending on prostate size 6