Auditory evoked potentials in the assessment of central nervous system effects of antimigraine drugs

Because the "intensity dependence" of cortical auditory evoked potentials ( IDAP) is under serotonergic control, it can be used to assess central antim igraine effects of 5HT(1B/1D) agonists. We measured IDAP before and 2 h aft er naratriptan (5 mg, n = 19) and zolmitriptan (5 mg, n=19) in healthy volu nteers, IDAP was expressed as the amplitude-stimulus intensity function ("A SF slope"). Naratriptan tended to increase ASF dope (mean difference 0.23+/ -0.62 mu V/10 dB, p=0.06) while zolmitriptan (0.08+/-0.95 mu V/10 db, p=0.3 5) did not. We assessed the suitability of IDAP for measuring central antim igraine drug effects using repeatability data (see companion paper). We cal culated the trade-off between the size of the expected drug effects (ASF sl ope difference) and the necessary sample size. Because of poor repeatabilit y 36 to 80 subjects are required to detect ASF slope changes in the 0.25-0. 5 mu V/10 db range. These data can be used to design trials using IDAP.