Background: Patch forms of glyceryl trinitrate (GTN), also known as nitroglyceril, have proved useful in the management of dysmenorrhea. Increased intrauterine pressure due to exaggerated myometrial contractions is an important factor in the pathogenesis of dysmenorrhea. In a recent study, it was found that GTN caused a significant reduction in the contraction frequency of human myometrial strips. The object of this study is to evaluate the efficacy of GTN ointment in treating primary dysmenorrhea.

Methods: In this double-blind randomized placebo-controlled study, we enrolled 112 unmarried subjects with the complaint of moderate to severe primary dysmenorrhea. They were between 18-30 years of age with normal BMI (19-27) and all had normal results upon examination by pelvic ultrasound. None of these patients had a history anemia, previous pelvic surgery or cardiovascular diseases. Randomly divided in two groups using odd and even numbers, 56 of the subjects received 5 mg 1% GTN ointment and another 56 received a placebo. Before starting the treatment, severity of pain was recorded using a visual scale method. Ointment A (GTN 1%) or ointment B (placebo) was applied to special papers which were in turn applied to the skin of the abdomen below the umbilicus, and left there for the entire treatment period of four hours. The severity of pain and side effects of the treatment were recorded at intervals of 15 min, 30 min, 1 h, 2 h and 4 h after application the treatment. After four hours, the treatment was removed and the skin checked for erythema.

Results: There was no difference in severity of pain 15 min after treatment, but pain was less severe in the GTN group from the 30-min interval through the 4-h interval, with the least pain felt at the 2-h interval. This decrease in pain lasted through the 4-h interval. Side effects, which were more common in the GTN group than the placebo group (P<0.05), included headache (48.3% vs. 19.5%, respectively), dizziness and flushing.

Conclusions: GTN performed well in relieving primary dysmenorrheal discomfort; however, the side effect of headache reduced its efficacy and tolerability.