Filitra 40 is marketed as containing vardenafil, a PDE5 inhibitor used to treat erectile dysfunction (ED). Vardenafil works by enhancing the nitric-oxide/cGMP pathway, relaxing smooth muscle and increasing blood flow to the penis when sexual stimulation occurs. This can help men achieve and maintain an erection. A key safety point concerns the 40 mg strength. Standard vardenafil prescribing information recommends 10 mg as the usual starting dose, with adjustment to 5–20 mg according to effectiveness and tolerability. 20 mg is the maximum recommended dose and the medicine should not be taken more than once daily.