Heat therapy has been a traditional remedy for dysmenorrhea, but only a few case reports evaluate its use. Akin and colleagues assessed whether topically applied heat could subjectively relieve menstrual pain.

Participants were selected from clinical patients and volunteers responding to advertisements. Criteria included age of at least 18 years, nonpregnant, using reliable contraception and a history and physical examination consistent with the diagnosis of primary dysmenorrhea. Participants were also required to have regular menstrual cycles and to achieve relief of menstrual pain using nonprescription analgesics. Exclusions included cutaneous lesions of the abdominal wall, microvascular disease (including diabetes), drug or alcohol abuse, any known or suspected contraindication to ibuprofen, and being (or having recently been) pregnant.

After a screening physical assessment, the participants were randomly assigned to one of four treatment groups. Each participant received an oral medication and a medical device to be worn on the lower abdomen adhering to the inside of the woman's underwear. The oral medication was either ibuprofen, in a dosage of 400 mg three times daily, or an identical placebo. The heat patch was either inactive or capable of providing low heat (38.9°C [102°F]) for 12 hours. Patients were unaware if they had the active patch, active oral medication, both, or two placebos. Pain relief was recorded by patients using a six-point scale. Patients also recorded skin conditions in the area of the patch. Quality of life was rated during the two-day study using a rating instrument designed to assess pre-menstrual and menstrual symptoms and their severity.

Of the 84 enrolled participants, 81 completed the study. The participants in the four groups were comparable in demographic and gynecologic characteristics. Participants in all three active treatment groups reported greater pain relief than participants in the unheated patch and placebo group. Overall, participants using both ibuprofen and the heated patch reported levels of pain relief similar to levels in the group using ibuprofen and an unheated patch. However, greater pain relief was achieved at three time points on the first day (at three, four and eight hours) among the participants using ibuprofen and wearing a heated patch. In participants treated with placebo and unheated patch, 35 percent achieved complete pain relief. When the unheated patch was used plus ibuprofen, 55 percent achieved complete pain relief. In the participants using heated patches, 68 percent achieved complete pain relief when ibuprofen was included in the therapy, and 70 percent when the patch was used with placebo medication. Two participants treated with heated patches and one using placebo reported skin redness. Each heat patch costs between $2.50 and $3.00.

The authors conclude that the heating patch appeared to be additive to ibuprofen therapy, with more rapid onset of pain relief compared with conventional oral medication used alone.