Guidelines for trials of drug treatments in tension-type headache. First edition: International Headache Society Committee on Clinical Trials.

The present guidelines were developed under the auspices of the International Headache Society because of the need ‘‘to improve the quality of controlled trials of drug treatments in tension-type headache’’. They follow the Guidelines for controlled trials of drugs in migraine (1) and are presented along the same lines. Good quality controlled trials are the only way to demonstrate convincingly the efficacy of a drug, and form the basis for international agreement on drug therapy. A controlled clinical trial in tension-type headache (TH) is a scientific experiment in which a relevant question is answered. The trial may be either pragmatic, questioning the impact on health of treatment, or explanatory, testing the efficacy of treatment in TH (2). These guidelines are principally for explanatory trials, since experience with clearly pragmatic trials in TH is almost non-existent. The traditional classification of drug trials into phases I–IV is largely avoided in these guidelines, since TH trials do not differ in this respect from trials in other conditions. For these and other issues concerning clinical trials in general, the reader should consult works on clinical trial methodology (2–5). Only issues of specific relevance to TH are taken into account here.