By Andrea Hargraves 
The professor states that there is no scientific study proving its use for physical activity. “From a physiopathological standpoint, it doesn't make sense to use phosphodiesterase inhibitors to gain muscle mass,” he says.
What can happen, the doctor says, is the so-called placebo effect. He adds: “There is autosuggestion: the person takes it and believes that he will get better, even if it is a flour pill. The placebo effect, yes, is scientifically proven to exist.”
We don't have long-term studies that show what might happen with early use of phosphodiesterase inhibitors, in terms of sexual dysfunction. But certainly, in people who start using it unnecessarily, the body begins to get used to it, tolerance begins more and it does not have the desired effect, if they need to use it later. Brivaldo Markman Son, cardiologist
This was also stated by urologist Fernando Faccio, coordinator of the Department of Andrology, Reproduction and Sexual Diseases of the Brazilian Society of Urology. He says: “There is a dependence on the patient to take it and feel safe so that he does not fail. This failure is very harmful and painful, and sometimes the patient avoids the activity if he does not take it.”
For patients with erectile dysfunction, the recommended use of tadalafil is generally 5 mg per day – but it may also be indicated on demand, i.e. consumed only when the patient intends to have intercourse. “Each time tadalafil is overused, the side effects will be hypotension (low blood pressure) and dizziness,” Fassio says.