A number of compounds are associated with headache, either due to exposure or withdrawal. The hangover is perhaps the most widely experienced.

In addition to alcohol, other compounds identified as causing headache include:3

·      nitric oxide

·      phosphodiesterase (PDE) inhibitors

·      carbon monoxide

·      foodstuffs eg monosodium glutamate (MSG)

·      cocaine

·      histamine

·      calcitonin gene-related peptide.

Non-analgesic medicines commonly linked to headache include atropine, digitalis, disulfiram, hydralazine, imipramine, nicotine, nifedipine, and nimodipine. Compounds commonly associated with withdrawal headaches include caffeine, opioids, oestrogens, and potentially corticosteroids, tricyclic antidepressants, selective serotonin reuptake inhibitors (SSRIs) and NSAIDs.3

ICHD-3(beta) defines medication-overuse headache as “headache occurring on 15 or more days per month developing as a consequence of regular overuse of acute or symptomatic headache medication (on 10 or more or 15 or more days per month, depending on the medication) for more than three months. It usually, but not invariably, resolves after the overuse is stopped.”