Sildenafil (better known as Viagra) is a male erectile dysfunction (impotence) drug developed by Pfizer. Its effect is to inhibit phosphodiesterase, which would otherwise break down cyclic GMP. Cyclic GMP can subsequently stimulate the effect of nitric oxide (NO), a substance capable of inducing an erection.

Tadalafil, sold under the brand name Cialis, is a medicine used to treat erectile dysfunction (ED), benign prostatic hyperplasia (BPH) and pulmonary arterial hypertension. It is an oral tablet. The onset is usually within half an hour and the duration is up to 36 hours.

Vardenafil is a medicine that increases blood flow and relaxes muscles in certain parts of the body. Used to treat erectile dysfunction (impotence). It belongs to a group of medicines called PDE5 inhibitors and works by increasing the blood flow in the penis, resulting in a strong erection.

Dapoxetine, marketed as Priligy, is a medicine used to treat premature ejaculation (PE) in men aged 18-64 years. Dapoxetine acts by inhibiting the serotonin transporter, increasing the effect of serotonin on postsynaptic cleavage and, as a result, promoting ejaculation delay. As a member of the family of selective serotonin reuptake inhibitors (SSRIs), dapoxetine was originally developed as an antidepressant. However, unlike other SSRIs, dapoxetine is absorbed and rapidly eliminated in the body. Due to its fast-acting properties, it is suitable for the treatment of PE, but not as an antidepressant.