Impotence to take sildenafil did not work, may be the choice of the dose is relatively small or after taking the lack of sexual stimulation, in addition, if itself the existence of neurological lesions or endocrine lesions, may eat sildenafil this kind of drug effect is not obvious. Sildenafil has 25mg, 50mg and 100mg, if you take a small dose of no obvious effect, you can according to the physical condition of the dose can be increased, need to adjust the dose of the drug in the guidance of the doctor. In addition sildenafil needs to be taken before sex, there is sexual stimulation to play a role in the effect, otherwise it is useless. If there are neurological diseases, such as spinal cord lesions, cerebral infarction, etc., taking sildenafil may not have a significant effect. If itself androgen secretion is insufficient, simply taking sildenafil is not effective, need to cooperate with androgen therapy. Therefore, if you take sildenafil and have no obvious effect on erectile dysfunction, you can increase the dosage first, and if you still have no effect, you need to go to the hospital for relevant examinations to exclude other diseases. It is recommended to go to a specialist for medication.