Why is the therapeutic effect of acute antimigraine drugs delayed? A review of controlled trials and hypotheses about the delay of effect

In randomised controlled trials (RCTs) of oral drug treatment of migraine attacks, efficacy is evaluated after 2 hours. The effect of oral naratriptan 2.5 mg with a maximum blood concentration (T max ) at 2 hours increases from 2 to 4 hours in RCTs. To check whether such a delayed effect is also present for other oral antimigraine drugs, we hand‐searched the literature for publications on RCTs reporting efficacy. Two triptans, 3 nonsteroidal anti‐inflammatory drugs (NSAIDs), a triptan combined with an NSAID and a calcitonin gene–related peptide receptor antagonist were evaluated for their therapeutic gain with determination of time to maximum effect (E max ). E max was compared with known T max from pharmacokinetic studies to estimate the delay to pain‐free. The delay in therapeutic gain varied from 1–2 hours for zolmitriptan 5 mg to 7 hours for naproxen 500 mg. An increase in effect from 2 to 4 hours was observed after eletriptan 40 mg, frovatriptan 2.5 mg and lasmiditan 200 mg, and after rizatriptan 10 mg (T max = 1 h) from 1 to 2 hours. This strongly indicates a general delay of effect in oral antimigraine drugs. A review of 5 possible effects of triptans on the trigemino‐vascular system did not yield a simple explanation for the delay. In addition, E max for triptans probably depends partly on the rise in plasma levels and not only on its maximum. The most likely explanation for the delay in effect is that a complex antimigraine system with more than 1 site of action is involved.