Tadfil is a phosphodiesterase (PDE) inhibitor that is prescribed to treat erectile dysfunction in men (impotence; inability to get or maintain an erection). It increases blood flow to the penis during sexual stimulation, aids in response to stimulation, and relaxes lung vessels. It is taken orally as a tablet, with or without food. The initial dosage is 10 mg once daily, at least 30 minutes before sexual activity, up to a maximum of 20 mg dose; if taken with strong CYP3A4 inhibitors, it is recommended to flush; wearing layers of clothing or summer clothing and staying in cool environments may help. Other side effects include headache, back pain, nose stuffiness, stomach pain, and heartburn, and eye changes are uncommon.