Abstract OBJECTIVE: To assess the efficacy and safety of sildenafil in primary erectile dysfunction. METHODS: 104 patients eligible for primary erectile dysfunction were divided into 2 groups: 46 cases in the non-pharmacological treatment group, who received instruction on sexual knowledge and skills; and 58 cases in the as-needed treatment group, who took sildenafil 50 mg orally 1h before coitus, with drug dosage adjustments based on the efficacy and tolerance of the treatment for more than 4 times in the pre-treatment period. The International Index of Erectile Function Questionnaire 5 Simplified Questions (IIEF-5) scores were compared before and after treatment to assess the overall clinical efficacy, the proportion of ED-free, and the incidence of adverse effects after treatment.Both groups were treated for 3 months, and their efficacy was reassessed at 1 and 3 months after drug discontinuation. RESULTS: At the end of 3 months of treatment, the median scores of IIEF-5 before and after treatment in the control group and the on-demand group were 5.2 and 12.6, 4.2 and 19.8, respectively; the number of ED-free patients was 12 (26.1%) and 56 (96.6%), and the overall clinical efficacy rate was 27.7% and 97.2%, respectively; the number of ED-free patients in the one-month discontinuation period was 8 (17.4%), and the percentage of 56 cases (96.6%) was 27.7% and 97.2%, respectively; and the total clinical efficacy rate was 8 (17.4%) and 56 cases (96.6%), 56 cases (96.6%), the total clinical effectiveness rate was 19.4% and 97.1% respectively; 7 cases (15.2%) and 55 cases (94.8%) without ED in 3 months after stopping the drug, the total clinical effectiveness rate was 16.4% and 96.4% respectively. The incidence of adverse reactions in the on-demand group (16 cases, 27.6%) was higher than that in the control group (5 cases, 10.9%), (P0.05); most of the adverse reactions were transient and mild, and gradually weakened and disappeared with the prolongation of the treatment time, and there were no patients who interrupted the medication due to adverse reactions. Conclusion: Sildenafil is safe and effective in the treatment of primary erectile dysfunction, and the proportion of ED-free at the end of treatment and at 1 and 3 months after discontinuation of the drug in the on-demand group and the total clinical effectiveness rate were significantly better than those in the control group, which showed good advantages in the maintenance of efficacy. Keywords Primary ED; pharmacotherapy; sildenafil. Oral phosphodiesterase type 5 (PDE5) inhibitors have become a first-line option for the treatment of erectile dysfunction (ED, Erectile Dysfunction) due to their favorable efficacy and safety profile. Primary ED, as a special type of ED, has been less reported in the past. We used sildenafil on-demand to treat 112 cases of primary ED to explore its efficacy and safety. Objects and methods 1. Objects There were 121 ED patients, aged 23-36 years, (29±6.7) years old, who met the enrollment criteria in the outpatient clinic of the male department of our hospital from July of 2009 to July of 2010. Before enrollment, all of them underwent informed consent counseling, and excluded organic lesions and genital developmental abnormalities after history inquiry and physical examination. 2, Inclusion criteria Newly married within one year or unmarried with a regular sexual partner and cohabitation for more than 1 month; erection hardness during sexual life was not enough to insert into the vagina or maintain thrusting, or erection maintenance time was not enough to complete a satisfactory sexual life; no history of sexual intercourse before marriage or cohabitation. 3. Exclusion criteria Those who have taken nitrates or applied other ED treatments and have recently participated in other clinical drug studies, those who have obvious anatomical malformations of the genitals, other abnormalities of sexual function, hypogonadism, serious psychological abnormalities, poorly controlled diabetes mellitus or untreated diabetic retinoproliferative degeneration, a history of alcoholism or drug abuse, a history of serious hematologic, renal, or hepatic disorders, secondary to spinal cord ED injury, hypotension or severe hypertensive disease, stroke, myocardial infarction, or other serious cardiovascular disease within the past 6 months; clinically significant abnormalities following a screening physical examination and safety trial. Spouses with sexual frigidity, vaginal spasm or stenosis, and couples who are not in good relationship. 4, experimental design Example patients were divided into 2 groups for treatment after enrollment: ① control group: those who were unwilling or refused medication, using the form of pictures, explaining in detail the anatomy and function of male and female external genitalia, the characteristics and differences between male and female sexual response cycle, and sexual skills guidance. ② On-demand medication group: on the basis of sexual knowledge and sexual skill instruction, take sildenafil 50mg orally 1h before coitus, once a day. Avoid alcohol and high-fat food before taking the drug, and take it on an empty stomach or 2h after meals; according to the efficacy and tolerance after the first 4 times of taking the drug, adjust the dosage to 100mg or 25mg, and according to the efficacy and tolerance, choose to discontinue or maintain the treatment. Both groups were observed for 3 months, and the efficacy was evaluated again at 1 month and 3 months after stopping the drug. International Erectile Function Score (IIEF-5): A total score of <25 was used as the diagnostic criterion for ED. According to the total score, the degree of ED was categorized into: no ED: >25 points; mild: 22~25 points; mild to moderate: 17~21 points; moderate: 11~16 points; and severe: 1~10 points. Overall clinical effectiveness was the change in the sum of IIEF-5 Q3 and Q4 scores at the end of treatment and at the final follow-up visit compared with baseline, and was categorized into 4 grades: ineffective ≤ 0; improved 0-1, effective 2-4, and significant ≥ 5. Overall clinical effectiveness was the Effective plus Significant Effect score. Sexual activity diary: record the number of sexual encounters per week, the date and number of tablets taken, whether intercourse was successful or not and the reasons for failure. Assessment of adverse events: enrolled patients underwent a complete physical examination, 12-lead electrocardiogram and laboratory tests, including routine blood and urine, liver and kidney function, electrolytes and lipids, and other biochemical tests during the screening period and at the end of drug administration. Patients were tested for sitting blood pressure and heart rate at each visit, and all observed or voluntarily provided adverse events were recorded. 6, Statistical methods The SPSS 11.5 software package was used, and the rank-sum test for multiple-sample comparisons was used to compare the groups before treatment and at the end of the 3-month treatment. Two-sided test was taken and P<0.05 was considered statistically significant. 7, Enrollment 121 cases were enrolled, 8 cases (6.6%) refused treatment or missed visits, 9 cases (7.4%) withdrew halfway due to poor efficacy, and 104 cases (92.9%) completed the 3-month treatment and were evaluated at 1 and 3 months after discontinuation of the drug. Diabetes mellitus, cardiovascular and endocrine disorders were all excluded from the past medical history, and the differences in age, disease duration, ED severity and pre-treatment IIEF-5 scores were not statistically significant between the two groups, and the basic patient profiles are detailed in Table 1.The patients were interested in the explanations of female sexuality, sexual counseling and techniques, the anatomical functions of the external genitalia and the male and female sexual response cycles, and indicated that they had never received any previous relevant Information.