Drug description:

Tadalafil is used in a treatment of erectile dysfunction in adult males. In order for tadalafil to be effective, sexual stimulation is required.
Tadalafil is not indicated for use by women. 
It is formulated as film coated tablets for an oral route of administration.

Mechanism of action:

Tadalafil is a selective, reversible inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). When sexual stimulation causes the local release of nitric oxide, inhibition of PDE5 by tadalafil produces increased levels of cGMP in the corpus cavernosum. This results in smooth muscle relaxation and inflow of blood into the penile tissues, thereby producing an erection. Tadalafil has no effect in the absence of sexual stimulation.