Can you take Viagra (sildenafil) and Cialis (tadalafil) at the same time?

Can You Take Viagra and Cialis Together?

No, you should not take Viagra (sildenafil) and Cialis (tadalafil) at the same time in standard clinical practice. Both medications are PDE5 inhibitors that work through the same mechanism, and combining them increases the risk of adverse events without providing additional clinical benefit for most patients 1.

Why Combining These Medications Is Not Recommended

Same Drug Class, Same Mechanism

• Both sildenafil and tadalafil are phosphodiesterase-5 (PDE5) inhibitors that work identically by enhancing nitric oxide-mediated vasodilation 2
• The American College of Physicians recommends initiating therapy with a single PDE5 inhibitor, not combining multiple agents from this class 1
• Evidence shows that combining PDE5 inhibitors with other PDE5 inhibitors was associated with more adverse events compared to using a single PDE5 inhibitor alone 1

Increased Risk Without Proven Benefit

• High-quality evidence demonstrates that men receiving PDE5 inhibitors experience more adverse events than placebo, with common side effects including headache, flushing, rhinitis, dyspepsia, visual disturbances, myalgia, and dizziness 1
• Combining two PDE5 inhibitors would amplify these vasodilatory side effects, particularly hypotension, headache, and flushing 2
• The incidence of serious adverse events with PDE5 inhibitors is less than 2%, but this risk would be unnecessarily elevated with combination therapy 2

The Proper Approach to PDE5 Inhibitor Therapy

Choose One Agent Based on Patient Preference

• The American College of Physicians recommends that clinicians base the choice of a specific PDE5 inhibitor on individual patient preferences, including ease of use, cost, and adverse effects profile 1
• Tadalafil has a significantly longer half-life (17.5 hours) compared to sildenafil (approximately 4 hours), providing a longer duration of action 2
• Tadalafil has lower rates of flushing compared to sildenafil, making it favorable for some patients 2

Optimize Dosing of a Single Agent

• For sildenafil: improvement in erectile function is related to higher doses (50 mg vs. 25 mg, but not necessarily 100 mg vs. 50 mg) 1
• For tadalafil: start with 10 mg as needed, which can be titrated to 20 mg based on response 2
• Higher doses are associated with greater efficacy but also greater risk for adverse effects 1

If One PDE5 Inhibitor Fails

• Switch to a different PDE5 inhibitor rather than combining them 3, 4, 5
• Consider adding testosterone replacement therapy for men with low testosterone levels (either as initial treatment or after PDE5 inhibitor failure) 2
• Low-quality evidence shows that adverse events did not differ between sildenafil alone versus sildenafil plus testosterone 1

Critical Safety Considerations

Absolute Contraindications

• Concurrent use of nitrates in any form (nitroglycerin, isosorbide dinitrate) is an absolute contraindication for any PDE5 inhibitor therapy, whether used alone or in combination 1
• This contraindication exists because PDE5 inhibitors potentiate the hypotensive effects of nitrates, potentially causing life-threatening hypotension 2

Cardiovascular Risk Assessment

• Patients with cardiovascular disease should be risk-stratified before initiating ED therapy 1, 2
• Management of ED should always be considered secondary to maintaining cardiovascular function 1

The Exception: Limited Research Context Only

• One small study (180 patients) evaluated tadalafil 5 mg once daily combined with sildenafil 50 mg as needed specifically at the early stage of treatment, showing some benefit in severe ED without increased adverse events 6
• However, this represents a specific research protocol (daily low-dose tadalafil plus as-needed sildenafil) rather than standard practice, and this approach has not been validated in larger trials or incorporated into clinical guidelines 6
• This is not equivalent to taking both medications simultaneously at standard doses

Bottom Line Algorithm

1. Start with one PDE5 inhibitor based on patient preference (duration of action, side effect profile, cost) 1, 2
2. Optimize the dose of that single agent before considering alternatives 1, 2
3. If inadequate response, switch to a different PDE5 inhibitor rather than combining 3, 4, 5
4. If still inadequate, consider adding testosterone (if levels are low) or other non-PDE5 inhibitor approaches 2
5. Never combine with nitrates under any circumstances 1, 2