Viagra in the Treatment of Primary Dysmenorrhea

The primary hypothesis is that a 100mg single dose of sildenafil citrate (Viagra) will have a higher improvement rate when compared to placebo in the treatment of moderate to severe primary dysmenorrhea.

It is well established that excess prostaglandin production in primary dysmenorrhea leads to ischemia of the uterine muscle, which consequently causes pelvic pain. A large number of drugs have been studied for pain relief in dysmenorrhea patients, with non-steroid anti-inflammatory drugs (NSAIDS) being the most effective with the overall success rate of more than 75%. Sildenafil citrate (Viagra) is an inhibitor that augments the vasodilatory effects of nitric oxide by preventing the degradation of Cyclic guanosine monophosphate (cGMP) in the uterine muscle. Sildenafil is commonly used in the treatment of male erectile dysfunction, pulmonary hypertension in children and adults, and in vitro fertilization. To date it has not been used in the treatment of primary dysmenorrhea.

The Primary Outcome Was Total Pain Relief Over 4 Hours (TOPAR4), Comparing a Single Dose of Sildenafil 100 mg to a Single Dose of Placebo.

The Total Pain Relief (TOPAR) Scale rates the level of pain relief on a scale of 0=None, 1=Mild, 2=Moderate, 3=Excellent, 4=Complete. The TOPAR scale was completed each hour after administration of study drug for a total of 4 hours. The 4 hourly scores were summed for a final TOPAR4 score that ranged between 0 and 16, with higher values indicating greater pain relief over time. Missing TOPAR scores after the first hour were imputed using the last-observation-carried-forward approach.

The Visual Analog Scale (VAS) assesses pain intensity. The scale is 100 mm long; the extremes of the scale are to the left, "no pain" and to the right, "worst pain I have ever felt." The VAS score is determined by measuring the distance (in mm) from the left side of the scale to the point that the patient marked. The score ranges from 0 to 100, with higher values indicating greater pain.

Inclusion Criteria: Primary dysmenorrhea at current visit, with a visual analogue scale (VAS) score of >35; pain defined as moderate or severe on a categorical of none, mild, moderate, severe. Exclusion Criteria: Secondary dysmenorrhea Any current medication Serious medical condition

Dmitrovic R, Kunselman AR, Legro RS. Sildenafil citrate in the treatment of pain in primary dysmenorrhea: a randomized controlled trial. Hum Reprod. 2013 Nov;28(11):2958-65. doi: 10.1093/humrep/det324. Epub 2013 Aug 6.