必利勁 is the trade name, generic name is Dapoxetine Hydrochloride Tablets; Viagra generally refers to Sildenafil Citrate, the two can be used together, but should be under the guidance of a doctor, it is recommended to take the drug one hour apart. Dapoxetine Hydrochloride is mainly used for the treatment of premature ejaculation and poor ejaculatory control and should be taken one to three hours before the start of sex. Its common adverse reactions include mild headache and nausea, etc. It is contraindicated for those who are allergic to dapoxetine and those who have significant cardiac pathology. Sildenafil citrate tablets are mainly used for the treatment of erectile dysfunction, and are recommended to be taken 30 minutes~1 hour after sexual intercourse. Its frequent adverse reactions include back pain, rash, dizziness, headache, visual abnormalities, etc. It is contraindicated for those who are allergic to sildenafil and those who use nitrate drugs. Dapoxetine hydrochloride and sildenafil citrate can be used in combination for the treatment of impotence and premature ejaculation, and have better clinical efficacy. However, the two should be taken separately with an interval of at least 1 hour. Please combine the medications under the supervision of a physician, and if you experience significant discomfort after using the medication, stop sexual activity and lie down to rest.