Study leader Richard Legro of Pennsylvania State College of Medicine said primary dysmenorrhea, also called PD, is the most common cause of pelvic pain in women. The current treatment is non-steroidal anti-inflammatory drugs, such as ibuprofen. However, ibuprofen does not work well for all women, and can be associated with ulcers and kidney damage when used chronically as it often is for PD.
However, sildenafil citrate, sold under the brand name Viagra, may help with pelvic pain because it can lead to dilation of the blood vessels. Previous research showed taking it orally can alleviate pelvic pain, but the incidence of side effects -- often headaches -- might be too high for routine use.
The researchers looked at administering sildenafil citrate vaginally, which had not yet been tried, to treat PD. They compared pain relief from sildenafil used vaginally with that of a placebo.
Penn State College of Medicine researchers worked with researchers at Nova Gradiska General Hospital in Croatia. They recruited women ages 18-35, who suffered from moderate to severe PD. Of the 29 women screened for the study, 25 were randomized to receive either sildenafil or a placebo drug.
Patients rated their pain over four consecutive hours.
The study, published in Human Reproduction, found sildenafil citrate administered vaginally alleviated acute menstrual pain with no reported side effects.
The researchers hypothesized that the drug would alleviate pain, which it does, but also that is does so by increasing blood flow. However, because uterine blood flow increased from both sildenafil and the placebo, the reason it alleviates pain is not yet known.