Non-steroidal anti-inflammatory drugs in the alleviation of primary dysmenorrhoeic pain

Avidon, Ingrid
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The cramping, and often debilitating, pain which women of child-bearing age experience in the lower abdomen just before, or during, menstruation, in the absence of any pelvic pathology, is called primary dysmenorrhoea. The aetiology of dysmenorrhoea is not fully understood and the condition is often poorly treated. The aim of my thesis is to contribute knowledge to the assessment and treatment of dysmenorrhoea, as well as objective measurement of the impact of dysmenorrhoea on physical activity and functional performance. I completed three separate studies, on three different groups of healthy young women with a history of moderate-to-severe primary dysmenorrhoea. I used the McGill Pain Questionnaire (MPQ) and the visual analogue scale (VAS), as indices of pain intensity, to assess the efficacy of three cycloxygenase (COX) inhibitors, covering a spectrum of COX-2 selectivity, in the treatment of dysmenorrhoea. The pain response index (PRI) and present pain index (PPI), calculated from the MPQ, and the VAS, were highly correlated as measures of intensity of dysmenorrhoeic pain. The COX-2 specific inhibitor rofecoxib, and the non-selective COX inhibitor diclofenac potassium, significantly decreased the duration of dysmenorrhoeic pain, compared to placebo and compared to meloxicam, a COX-2 selective inhibitor, and were equally effective in relieving menstrual pain. Women with dysmenorrhoea subjectively report decreased physical activity, but no studies have attempted to quantify the decrease in exercise performance, or functional ability resulting from dysmenorrhoea, in a standardized laboratory protocol when women perform structured physical activity. Furthermore, no method or tool has been described which measures the the effect of dysmenorrhoea on the activity of daily life. I assessed whether an activity data logger (actigraphy), worn on the hip, was able to detect, and quantify, pain-reduced physical activity levels in women with dysmenorrhoea going about their daily lives. In the laboratory protocol I showed that moderate-to-severe dysmenorrhoea, but not the act of menstruation without pain, decreased the women’s ability to bend over and stretch upwards, and to perform exercise that required the use of their lower limb muscles. Administration of diclofenac potassium attenuated dysmenorrhoea and restored exercise performance and functional ability to levels attained when the women were in a pain-free phase of the menstrual cycle. I showed that activity data loggers, worn on the hip of each woman, were able to detect and quantify painreduced activity of daily life. Moderate-to-severe menstrual pain, but not menstruation itself, decreased the women’s physical activity, as measured by the data loggers, to about two-thirds of the activity measured when they were in a pain-free phase of the menstrual cycle In conclusion, I have added further knowledge to the assessment and treatment of dysmenorrhoea. The VAS and the MPQ, incorporating the PRI and PPI, are interchangeable indices of intensity of dysmenorrhoea and, depending on the educational status of the cohort, any one of the indices is suitable for assessment of intensity of pain. Rofecoxib and diclofenac potassium, two cycloxygenase inhibitors with differing COX-2 specificity, are excellent pharmacological therapies for the treatment of dysmenorrhoea. Objective assessment of physical activity, via activity data loggers, is a potentially useful tool to investigate the effects of dysmenorrhoea on structured physical activity and the activity of daily life, and for measuring pain-related debilitation and its management.