Parenteral indomethacin (the INDOTEST) in cluster headache

The interval between indomethacin administration and clinical response may be extremely relevant in the assessment of chronic paroxysmal hemicrania (CPH) and other unilateral headache disorders like cluster headache (CH), with which CPH can be confounded. Indomethacin is inactive in CH; however, in some anecdotal reports in recent years, doubt has been cast on the ineffectiveness of indomethacin in CH. In this study, we have re-assessed the effect of indomethacin treatment in a group of 18 patients with episodic CH (three females and 15 males). From the day 8 of the active period, indomethacin 100 mg i.m. was administered every 12 h, for 2 consecutive days, in an open fashion. The mean daily attack frequency before the test (1.6 +/- 0.6) was not statistically different from that on day 1 (2.1 +/- 0.9) and day 2 (1.9 +/- 0.8) after indomethacin administration. The mean interval between indomethacin injection and the following attack (day 1 and day 2) was 4.6 + 1.1 h. We did not observe any refractory period in any patient after indomethacin. Since the 'expected' attack occurred when there theoretically could have been a protective effect after indomethacin administration, it can be reasonably assumed that there is no such protective effect. The use of a test dose of 100 mg i.m. indomethacin (INDOTEST) appears to provide a clear-cut answer in this situation. It may be a useful tool for a proper clinical assessment of unilateral headache with relatively short-lasting attacks when problems of classification arise. A correct diagnosis of CPH or CH is important, since a CPH diagnosis may imply a lifelong treatment with a potentially noxious drug.