Generic Tadacip 20 One medicine in particular, Viagra, is categorized as a phosphodiesterase type 5 (PDE5) inhibitor. Men with erectile dysfunction (ED) are the main patients for this medication. Tadalafil, the same active component found in the well-known drug Viagra, is also included in Tadacip. When a man is sexually aroused, sildenafil citrate helps him attain and sustain a hard erection by boosting blood flow to the penis.