Central Nervous System toxicity of mefenamic acid overdose compared to other NSAIDs: an analysis of cases reported to the United Kingdom National Poisons Information Service

A Kamour, Siobhan Crichton, G Cooper, D J Lupton, M Eddleston, J A Vale, J P Thompson, S H L Thomas

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22 Citations (Scopus)

Abstract

AIMS: Case reports and small case series suggest increased Central Nervous System (CNS) toxicity especially convulsions, after overdose of mefenamic acid, compared with other NSAIDs, but comparative epidemiological studies have not been conducted. This study compared rates of CNS toxicity after overdose between mefenamic acid, ibuprofen, diclofenac and naproxen, as reported in telephone enquiries to the United Kingdom National Poisons Information Service (NPIS).

METHODS: NPIS telephone enquiries related to the four NSAIDs received between January 2007 and December 2013 were analysed, comparing the frequency of reported CNS toxicity (convulsions, altered conscious level, agitation or aggression, confusion or disorientation) using multivariable logistic regression.

RESULTS: Of 22,937 patient-specific telephone enquiries, 10,398 did not involve co-ingestion of other substances (mefenamic acid 461, ibuprofen 8090, diclofenac 1300, naproxen 547). Patients taking mefenamic acid were younger and more commonly female than those using other NSAIDs. Those ingesting mefenamic acid were more likely to experience CNS toxicity than those ingesting the other NSAIDs combined (adjusted OR 7.77, 95% CI 5.68 to 10.62), especially convulsions (adjusted OR 81.5, 95% CI 27.8 to 238.8). Predictors of CNS toxicity included reported dose and age, but not gender.

CONCLUSIONS: Mefenamic acid overdose is associated with a much larger and dose-related risk of central nervous system toxicity, especially convulsions, compared with overdose of other NSAIDs. The benefit-risk profile of mefenamic acid should now be re-evaluated in light of effective and less toxic alternatives.

Original languageEnglish
JournalBritish Journal of Clinical Pharmacology
Early online date26 Oct 2016
DOIs
Publication statusE-pub ahead of print - 26 Oct 2016

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