Impotence taking tadalafil is ineffective may be related to taking too small a dose, taking too short a time, not receiving sexual stimulation after taking the drug and other factors. 1. Taking too small a dose: tadalafil can be used to treat impotence, but impotence patients take tadalafil dose is not enough, tadalafil can not play the desired effect, then there will be the case of ineffective after taking the drug. 2. too short of time: tadalafil needs a period of time to play a role, too short of time to play a role, it is recommended that impotence patients should be reasonable planning to take tadalafil time. 3. not receive sexual stimulation after taking the drug: impotence patients take tadalafil need to receive sexual stimulation in order to play, if you do not receive sexual stimulation, tadalafil can not play the ideal drug. Taking tadalafil may cause headache, back pain, dyspepsia, nosebleed and other adverse reactions, taking guanylate cyclase stimulant, nitrates are prohibited during the period of drugs, tadalafil allergy is prohibited. Impotence patients taking tadalafil need to be guided by a professional doctor, not to be abused.