After taking sildenafil midnight very hard, not to eat it is very hard to hard, consider is to produce a dependence on the drug, or have obvious psychological disorder. 1. Dependence on the drug: If the phenomenon of taking sildenafil in the middle of the night is very hard, it is difficult to harden without eating it, considering that it may be a psychological dependence on the drug. It is generally not recommended to take sildenafil for a long time, otherwise it is easy to produce psychological dependence on the drug, once the drug will affect the normal erection. 2. Psychological disorders: If you are psychologically impotent, there is too much psychological pressure, upset, anxiety before sex, just simply taking sildenafil tablets can only temporarily alleviate the symptoms, can not completely solve the problem, so once you stop taking the drug, impotence will reappear, the penis can not be normal erection. Taking sildenafil need to know the relevant contraindications, generally require allergy to drugs, liver function impairment, and renal function impairment is prohibited. Patients with cardiovascular disease, caution. After taking sildenafil, some patients may experience tachycardia, palpitations, etc. If it is only a mild manifestation, no special treatment is needed; if there is a serious palpitation accompanied by panic and shortness of breath, the drug should be stopped promptly. Taking sildenafil is recommended to follow the doctor’s advice, not unauthorized medication, in order to avoid adverse reactions.