There is No FDA-Approved Combination Drug of Sildenafil and Tadalafil
Sildenafil and tadalafil are not combined into a single pharmaceutical product, and combining these two PDE-5 inhibitors is explicitly contraindicated. Both drugs work through the same mechanism (phosphodiesterase type-5 inhibition), and using them together provides no additional benefit while significantly increasing the risk of adverse effects.
Why These Drugs Should Not Be Combined
Contraindication Based on Drug Labels
The FDA labeling for both medications is clear on this point:
- Tadalafil label explicitly states: "Do not use other ED medicines or ED treatments while taking tadalafil tablets" 1
- Sildenafil label warns: "The safety and efficacy of combinations of sildenafil tablets, 20 mg with sildenafil citrate tablets, 25 mg, 50 mg and 100 mg or other PDE-5 inhibitors have not been studied. Inform patients taking sildenafil tablets, 20 mg not to take sildenafil citrate tablets, 25 mg, 50 mg and 100 mg or other PDE-5 inhibitors" 2
Clinical Guideline Evidence
The American College of Physicians guidelines on erectile dysfunction treatment make no mention of combining different PDE-5 inhibitors as a therapeutic strategy 3. When discussing combination therapy, the guidelines only reference combining PDE-5 inhibitors with non-PDE-5 inhibitor therapies (such as psychotherapy, hormonal treatments, or other drug classes) 3.
What the Research Actually Shows
One small study (n=180) examined combining tadalafil 5mg daily with sildenafil 50mg "as needed" for severe erectile dysfunction 4. While this showed some improvement in IIEF-5 scores, this approach:
- Is not FDA-approved
- Contradicts drug labeling warnings
- Increases risk of adverse events (headache, flushing, hypotension, visual disturbances)
- Has not been validated in larger trials or long-term studies
The Correct Clinical Approach
If a patient fails to respond adequately to one PDE-5 inhibitor, the appropriate strategy is:
- Optimize dosing of the current agent (e.g., sildenafil up to 100mg or tadalafil up to 20mg) 3
- Switch to a different PDE-5 inhibitor rather than combining them - the guidelines note insufficient evidence to determine superiority between agents 3
- Add a non-PDE-5 inhibitor therapy if monotherapy fails - such as testosterone (in hypogonadal men), psychotherapy, or other adjunctive treatments 3
Common Pitfall to Avoid
Do not interpret "combination therapy" in the erectile dysfunction literature as meaning combining two PDE-5 inhibitors. The term refers to combining a PDE-5 inhibitor with a different drug class or therapeutic modality 3.
Safety Concerns with Dual PDE-5 Inhibition
Both drugs cause vasodilation through the same pathway. Combining them amplifies risks without proven additional efficacy:
- Hypotension - particularly dangerous with concurrent nitrate use, alpha-blockers, or antihypertensives 1
- Visual disturbances - including risk of NAION (non-arteritic anterior ischemic optic neuropathy) 2
- Hearing loss - temporal association with PDE-5 inhibitor use 2, 5
- Priapism - prolonged erection requiring emergency intervention 2
The answer is straightforward: there is no combination drug, and these medications should not be used together.