Analgesics for dysmenorrhoea
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Dysmenorrhoea affects many women of reproductive age, and is a frequent cause of time lost from work or school as well as interfering with daily living. Treatment is usually with NSAIDs and minor analgesics. A systematic review [1] tells us how effective these are for primary dysmenorrhoea.
Search
Randomised trials were sought using a number of search strategies, including requests for information from manufacturers. Studies had to be randomised, and primary dysmenorrhoea was defined as a history of painful menstrual cycles and exclusion of organic causes by physical examination.
The main outcome was pain relief of at least moderate intensity, and the main comparison was with placebo. Secondary outcomes were women needing rescue analgesics, women experiencing restriction of daily living and women experiencing absence from work or school. Adverse effects were also examined.
Results
Most trials were double-blind of either parallel or cross-over design, predominantly comparing the test analgesic with placebo.
Pain relief
The results for pain relief are shown in the Figure and Table 1.
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Table 1: Effectiveness of analgesics for pain relief of primary dysmenorrhoea
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Analgesic
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Number of Trials
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Number of patients
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Percent improved with analgesic
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Percent improved with placebo
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Relative benefit (95% CI)
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NNT (95% CI)
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Naproxen
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13
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1706
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59
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17
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3.4 (2.9 to 4.0)
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2.4 (2.2 to 2.7)
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Ibuprofen
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9
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599
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70
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31
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2.2 (1.9 to 2.7)
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2.6 (2.2 to 3.2)
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Mefenamic acid
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3
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518
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64
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31
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2.1 (1.7 to 2.6)
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3.0 (2.4 to 4.0)
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Aspirin
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5
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416
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29
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18
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1.6 (1.1 to 2.2)
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9.2 (5.3 to 35)
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Compared with placebo, naproxen (550 or 275 mg four times daily), ibuprofen (400 mg four times daily) and mefenamic acid (250-500 mg four times daily) had numbers needed to treat of between 2.4 and 3.0, with overlapping 95% confidence intervals, indicating no real difference between them. Five trials of aspirin (650 mg four times daily) had a much higher NNT of 9.2, with no overlap of confidence intervals with the NSAIDs. One comparison between paracetamol (650 mg four times daily) and placebo showed no difference between them.
Restriction of daily living
Women taking naproxen or ibuprofen were less likely to have restrictions of daily living (Table 2).
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Table 2: Effectiveness of analgesics on reducing restriction of daily life and absence from work or school caused by primary dysmenorrhoea
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Analgesic
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Number of Trials
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Number of patients
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Percent affected with analgesic
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Percent affected with placebo
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Relative benefit (95% CI)
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NNT (95% CI)
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Reducing restriction of daily living
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Naproxen
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7
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1341
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60
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86
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0.69 (0.64 to 0.74)
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3.8 (3.2 to 4.6)
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Ibuprofen
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3
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234
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12
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55
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0.22 (0.14 to 0.38)
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2.4 (1.9 to 3.2)
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Aspirin
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3
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203
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50
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62
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0.80 (0.62 to 1.03)
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8.0 (3.8 to >100)
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Reducing absence from work or school
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Naproxen
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7
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1345
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8
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34
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0.24 (0.18 to 0.32)
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3.9 (3.3 to 4.6)
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The NNTs were 3.8 ( 3.2 to 4.6) for naproxen and 2.4 (1.9 to 3.2) for ibuprofen. Aspirin did not have this beneficial effect, and the point estimate for the NNT was 8. There were no data on mefenamic acid.
Absence from work or school
Naproxen reduced greatly (by about 70%) the amount of time away from work or school (Table 2). The NNT was 3.9 (3.3 to 4.6). One study on ibuprofen mirrored this effect, and one study on aspirin did not have this beneficial effect. There were no data on mefenamic acid.
Adverse effects
Adverse effects were mainly nausea, dizziness and headache. There was a suggestion that naproxen caused more adverse effects (mainly nausea), but the power of studies to detect this was low and confidence intervals wide.
Comment
This is a well-done systematic review which demonstrated that naproxen, ibuprofen and mefenamic acid are effective. Aspirin was less effective and paracetamol 650 mg was not effective in a single study. The authors conclude that, based on efficacy and absence of common adverse effects, ibuprofen is probably the treatment of choice.
The only complaint one could have is the issue of dose. It would be helpful to know the NNTs at particular dose levels, though we suspect that the authors reflect what they found in the original reports.
Bandolier wishes to thank the authors for making original data available.
Reference:
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WY Zhang, A Li Wan Po. Efficacy of minor analgesics in primary dysmenorrhoea: a systematic review. British Journal of Obstetrics and Gynaecology 1998 105: 780-9.
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