CRD Summary: The authors concluded that meperidine is less effective for migraine headache than dihydroergotamine regimens and may be more likely to cause adverse events. Meperidine may also be less effective than antiemetics. A degree of caution may be necessary in interpreting these conclusions because the primary trials were small, their quality was mixed and there were marked differences between them.

[Intramuscular meperidine/pethidine (usually in conjunction with an antihistamine) or butorphanol were compared with intramuscular or intravenous dihydroergotamine (with or without antiemetics), antiemetics alone or ketorolac. The dose of meperidine was usually 75 milligrams (mgs) but ranged from 50 mgs to 1.5 mgs per kilogram (kg). Four different antiemetics were compared with the opioids (chlorpromazine, methotrimeprazine, droperidol and metoclopramide).]

CRD Commentary: The objectives and inclusion criteria of the review were clear and a wide range of relevant sources were searched for published and unpublished studies, without language restriction. The processes of validity assessment and data extraction were conducted by more than one independent reviewer, but the preliminary screening of studies for selection was conducted by a single reviewer, which increased the potential bias and error in this process. The Jadad scale was used to evaluate study quality but this scale has limited scope. No details were reported on relevant methodological characteristics of the included trials such as allocation concealment and follow-up rates. Relevant statistical methods appear to have been used to combine the trials and assess heterogeneity. Potential reasons for the heterogeneity detected were well addressed in the text, along with other potential biases such as small trial size and possible publication bias. The review was mostly well conducted but a degree of caution may be necessary in interpreting the authors' conclusions because the primary trials were small, their quality was mixed and there was marked heterogeneity between them.