J. Corbo et al., Randomized clinical trial of intravenous magnesium sulfate as an adjunctive medication for emergency department treatment of migraine headache, ANN EMERG M, 38(6), 2001, pp. 621-627
Study objective: We test the hypothesis that intravenous magnesium sulfate
is an effective adjunctive medication for treatment of acute migraine.
Methods: In this randomized, double-blind, placebo-controlled trial, adults
presenting to 2 urban emergency departments with headache meeting Internat
ional Headache Society criteria for acute migraine received either 20 mg of
intravenous metoclopramide plus 2 g of intravenous magnesium sulfate or 20
mg of intravenous metoclopramide plus a placebo of intravenous saline solu
tion at 15-minute intervals for a maximum of 3 doses or until pain relief o
ccurred. At 0, 15, 30, and 45 minutes, patients recorded pain intensity usi
ng a standard visual analog scale (VAS). The primary study end point was th
e between-group difference in pain improvement when initial and final VAS s
cores were compared.
Results: Of 44 patients enrolled (21 randomized to metoclopramide plus magn
esium and 23 to metoclopramide plus placebo), 42 (95%) were women. Baseline
features were comparable in both groups. Each group experienced a more tha
n 50-mm improvement in VAS score during the study. However, this improvemen
t was smaller in the magnesium group for the primary end point (16-mm diffe
rence favoring placebo [95% confidence interval (CI) -2 to 34 mm]), as was
the proportion with normal functional status at their final rating (36% abs
olute difference also favoring placebo [95% Cl 7% to 65%]). Using a 50% red
uction in pain to dichotomize VAS scores, the number needed to harm with ma
gnesium plus metoclopramide versus metoclopramide alone is 4 patients (95%
Cl 2 to 36).
Conclusion: Although this result was unexpected, our data suggest that the
addition of magnesium to metoclopramide may attenuate the effectiveness of
metoclopramide in relieving migraine. Counter therapeutic cerebral vasodila
tation caused by magnesium is a plausible, although unproven, explanation f
or this finding. Because of the preponderance of women in our trial, these
data may not be generalizable to men.