There should be no issues with taking two PDE5 inhibitors at the same time. But no benefit either as the effect should be the same as taking a larger dose of one drug.
That's not true and the advice is that you should not mix them.
No — you should not take two different prescription erectile dysfunction (ED) drugs at the same time.
Key points:
Combining PDE5 inhibitors (sildenafil, tadalafil, vardenafil, avanafil) can increase risk of severe side effects (prolonged low blood pressure, fainting, priapism, excessive drug exposure).
Never mix a PDE5 inhibitor with nitrates or nitric‑oxide donors — this can cause life‑threatening hypotension.
If one ED drug doesn’t work or causes side effects, talk to your prescriber about dose adjustment, switching agents, treating underlying causes, or alternative therapies (vacuum devices, injections, intraurethral pellets, hormones, psychotherapy).
If you experience chest pain, severe dizziness, fainting, or an erection lasting >4 hours (priapism), seek emergency care
I also think that taking longer acting ED medication such as Cialis in hot weather means you need to stay hydrated or you are more at risk of fainting.