A randomized clinical trial of sildenafil plus clomiphene citrate to improve the success rate of ovulation induction in patients with unexplained infertility

Int J Gynaecol Obstet. 2020 Jul;150(1):72-76. doi: 10.1002/ijgo.13159. Epub 2020 May 7.


Objectives: To investigate the role of sildenafil citrate in improving ovulation induction success rate in women with unexplained infertility.

Methods: A randomized clinical trial from January to December 2018 of 80 women with unexplained infertility randomized into two groups. Both groups received 100 mg clomiphene citrate once daily from days 3-7 of the menstrual cycle. The study group also received 25 mg oral sildenafil citrate twice daily from days 8-12 of the same cycle. Transvaginal ultrasound assessed ovulation, endometrial thickness, and number of follicles. Pregnancy was assessed 2 weeks after ovulation. Primary outcome measures were endometrial thickness, number of mature follicles, and pregnancy rates.

Results: Pregnancy rates (26 (65%) and 16 (40%), P=0.043) and endometrial thickness (10.4 ± 1.4 and 9.2 ± 1.9, P=0.007) were significantly higher in the study group. More women in the study group reported adverse effects compared with the control group (17 [42.5%] vs 9 [22.5%]; P=0.034), with headache the most common adverse effect in the study group, reported by 8 (20.0%) patients.

Conclusion: Adding sildenafil citrate improved ovulation success rate and increased pregnancy rate.

Pan african clinical trial registry: PACTR201907658492123.

Keywords: Clomiphene citrate; Infertility; Ovulation induction; Pregnancy; Randomized clinical trial; Sildenafil.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Drug Therapy, Combination
  • Female
  • Fertility Agents, Female / administration & dosage*
  • Fertility Agents, Female / adverse effects
  • Humans
  • Infertility, Female / drug therapy*
  • Ovarian Follicle / drug effects
  • Ovulation Induction / methods*
  • Pregnancy
  • Pregnancy Rate
  • Sildenafil Citrate / administration & dosage*
  • Sildenafil Citrate / adverse effects
  • Sildenafil Citrate / therapeutic use
  • Young Adult


  • Fertility Agents, Female
  • Sildenafil Citrate