HERSHEY, Pa. --Women with moderate to severe menstrual cramps may find relief in a class of erectile dysfunction drugs, according to a team of researchers led by Penn State College of Medicine's Richard Legro.

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.

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 shows that taking it orally can alleviate pelvic pain, but the incidence of side effects -- often headaches -- may 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 use of sildenafil vaginally with that of a placebo. Results were published in Human Reproduction.

Penn State College of Medicine researchers worked with researchers at Nova Gradiska General Hospital in Croatia. They recruited women 18 to 35 years old 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. Sildenafil citrate administered vaginally alleviates acute menstrual pain with no reported side effects. 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.

"If future studies confirm these findings, sildenafil may become a treatment option for patients with PD," said Legro, professor of obstetrics and gynecology and public health sciences. "Since PD is a condition that most women suffer from and seek treatment for at some points in their lives, the quest for new medication is justified."

Larger studies must be completed to validate the small sample of this study, and additional research is needed to see whether sildenafil changes the menstrual bleeding pattern.

Also on this study were Alan R. Kunselman, Penn State College of Medicine, and R. Dmitrovic, BetaPlus Center for Reproductive Medicine, Croatia.

The National Institutes of Health funded this study.