To update the evidence from rigorous clinical trials, for or against the efficacy of feverfew for the prevention of migraines. In addition, to provide a safety profile of this herbal remedy.

MEDLINE, EMBASE, BIOSIS Previews, CISCOM and the Cochrane Library were searched from the database inception to December 1999. The search terms included 'feverfew', 'Tanacetum parthenium', 'Chrysanthemum parthenium', 'Mutterkraut', 'headache' and 'migraine'. The bibliographies of the identified articles were searched manually, and the authors' own files were examined. Leading manufacturers of feverfew were asked to contribute published and unpublished material. There were no restrictions regarding publication language.

Study designs of evaluations included in the review

Double-blind, placebo-controlled, randomised controlled trials (RCTs) were included.

Specific interventions included in the review

Feverfew used for migraine prophylaxis. Studies were excluded if they were not performed on feverfew monopreparations. The dose ranged from 6.25 to 143 mg/day. The duration of treatment ranged from 1 to 6 months.

Participants included in the review

Patients with migraine were included. The patients were aged from 9 to 72 years.

Outcomes assessed in the review

No inclusion criteria relating to the outcomes were reported. The outcomes reported included: the frequency, duration and severity of headache; the incidence and severity of nausea and vomiting; the effect on serotonin uptake and platelet activity; the number of work days lost; pain intensity; and sensitivity to noise and light.

How were decisions on the relevance of primary studies made?

The authors do not state how the papers were selected for the review, or how many of the reviewers performed the selection.

The studies were assessed for methodological quality according to the criteria of Jadad et al. (see Other Publications of Related Interest). Studies were scored on a scale of 1 to 5. The authors do not state how the papers were assessed for quality, or how many of the reviewers performed the quality assessment.

The data were extracted independently by two reviewers using a standardised, predefined procedure. Data were extracted on the following: author; study design; the number of patients; the type (e.g. capsule), dose and duration of medication; the main outcome measures; and the results.

How were the studies combined?

A meta-analysis was considered, but was unfeasible due to the lack of a common outcome measure across the studies. A narrative synthesis was therefore presented.

How were differences between studies investigated?

Differences between the studies were discussed.

Six RCTs involving 363 patients were included; of these, 4 studies used a crossover design.

Four studies, which scored 3 to 4 points on the Jadad scale, reported positive results favouring feverfew. One study, which scored 5 points, reported negative effects. The other study, which found no effect of treatment, did not look at clinical outcomes; it looked at serotonin uptake and platelet activity. The frequency of migraine was positively affected by feverfew in 3 trials. Feverfew reduced the severity of migraine in 1 trial, while 2 studies reported no such effect. The incidence of nausea and vomiting was positively affected in 2 out of 4 trials, while severity was reduced in 1 study.

Feverfew was generally well tolerated and adverse effects were usually mild and reversible. Two studies reported a higher incidence of adverse effects in the placebo group, and one a similar incidence, compared with the feverfew group. In total, three withdrawals were necessitated by adverse effects in the feverfew groups.

The results favoured feverfew over placebo as a preventive treatment for migraine. However, several caveats prevented firm conclusions as to the efficacy of feverfew. Major safety problems do not seem to exist.

This was a good review of the area. A thorough literature search was conducted, which included attempts to locate unpublished studies; it is unlikely that important studies were missed. The inclusion criteria were stated clearly and study quality was assessed using a validated checklist. Details of how the data were extracted were provided, although there were no details of how studies were assessed for relevance or quality. Appropriate details of the studies were presented in tables, and the narrative synthesis provided a clear summary of the results.

The authors' conclusions were supported by the results presented.

The authors did not state any implications for further research and practice.

Jadad AR, Moore RA, Carroll D, Jenkinson C, Reynolds DJ, Gavaghan DJ, et al. Assessing the quality of reports of randomized clinical trials: is blinding necessary? Control Clin Trials 1996;17:1-12.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.