The indomethacin-responsive headache disorders consist of a group of conditions with a particularly good response to indomethacin. Two of the trigeminal autonomic cephalalgias are included, which are hemicrania continua and paroxysmal hemicrania. Other conditions are Valsalva-induced headaches (i.e. cough headache, exercise headache, and sex headache), primary stabbing headache, and hypnic headache. (VanderPluym, 2015)
This exact mechanism of action is not yet well understood; however, some explanations have been proposed. Since indomethacin is a strong non-steroidal anti-inflammatory, its effect could be related to the inhibition of the cyclooxygenase enzymes. Other reasons include the reduction of cerebral blood flow and the inhibition of nitric oxide. Nitric oxide is one of the fundamental molecules involved in the regulation of cerebral metabolic activity and blood flow. (Villar-Martínez et al, 2021).
Why to perform an indomethacin test (Indotest)
To predict the chronic responsiveness to indomethacin therapy. (Baldacci F. et al, 2008)
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How to perform the test
There are several protocols and dosages that have been used to detect indomethacin responsiveness. (Bordini et al, 2016) A parenteral dose of 100 mg should provide headache relief in no more than 30 minutes. (Antonaci F. et al, 2003) A lower parenteral dose of 50 mg takes around 50 minutes to be effective. (Baldacci F. et al, 2008) In addition, oral indomethacin could be used as a test as well. 100 mg orally per day is expected to reduce the frequency of headache attacks by 50% within at least seven days (Monta A. et al, 2021). Despite the benefit of the Indotest, the incidence of adverse events is high. For this reason, patients must be co-treated with a gastroprotective agent. (Myers et al, 2022)
What to do if it fails
Other classes of medications such as selective cyclooxygenase-2 inhibitors (e.g., celecoxib), anti-epileptic agents (e.g., topiramate), calcium channel blockers (verapamil, flunarizine), melatonin, and local nerve blocks with anesthetic and steroids have been shown to be effective in case reports and series. (Zhu et al, 2015) Furthermore, there have been several reports on the efficacy of serotonin and norepinephrine reuptake inhibitors (e.g., Venlafaxine) for hemicrania continua. (Dora et al, 2022)
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- Myers KA, Barmherzig R, Raj NR, Berrahmoune S, Ingelmo P, Saint-Martin C, Khan AQ, Kouri M, Morris C, Hershey AD, Kacperski J, Kabbouche MA, Mohamed N, Rao RR, Lagman-Bartolome AM, Gelfand AA, Szperka CL, Orr SL. The spectrum of indomethacin-responsive headaches in children and adolescents.
- Cephalalgia. 2022 Jul;42(8):793-797. doi: 10.1177/03331024221076483. Epub 2022 Mar 18. PMID: 35302385; PMCID: PMC9218410.
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- Dora B, Demir-Dora D. Indomethacin Resistant Hemicrania Continua Responsive to Venlafaxine. Neurol India. 2022 Jul-Aug;70(4):1670. doi: 10.4103/0028-3886.355083. PMID: 36076682.