Medication-overuse headache: A pharmacovigilance study in France.

BACKGROUND: Overusing medication for primary headaches or other medical conditions can lead to dependency and medication-overuse headache (MOH) as an adverse drug reaction (ADR).

OBJECTIVES: To analyse reports of ADRs associated with MOH recorded in the French national pharmacovigilance database (FPVD).

METHODS: This retrospective study selected all MOH cases reported in the FPVD from January 2000 to June 2023. A search of the High-Level Group Term "headache" was performed for drugs classified under ATC codes for the musculoskeletal and nervous systems. Specific keywords were searched in report narratives to further reduce their number. Voluntary intoxication reports were excluded. Only MOH cases according to the International Classification of Headache Disorders or with a medical diagnosis of MOH were considered.

RESULTS: Among the 2674 reports associated with the HLGT "headache", for 649 ATC drug codes, only 234 reports correspond to MOH, primarily notified by physicians. The median age was 45 years (IQR: 32-56), with 74.4% females and approximately 61.0% having pre-existing primary headaches. In all, 53.4% of the reports were classified as serious. Among patients, 84.2% had an isolated "headache" as the ADR. One drug was suspected in 47.4% of cases, two drugs in 29.1%, and three or more in 23.5%. In total, 473 suspected drugs, corresponding to 104 active ingredients, were involved, including analgesics (63.0%), in particular, acetaminophen-containing drugs, opioids, triptans and ergots, and non-steroidal anti-inflammatory drugs (12.7%). Antiepileptics and psycholeptics were found in 6.6% and 6.1% of cases, respectively. Drug withdrawal was successful in 84.6% of drug-discontinuation cases. Warnings about MOH are mentioned in the summary of product characteristics (SmPCs) for triptans, ergots, and certain acetaminophen-containing drugs, but not other drug classes.

CONCLUSIONS: Certain drug classes show a high reporting rate of MOH and caution should be exercised when prescribing these drugs. Notably, warnings about MOH must be mentioned in the SmPC of all concerned drug classes.