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Cephalalgia. 2013 Jan;33(1):52-64. doi: 10.1177/0333102412467512. Epub 2012 Nov 9.

Medication-overuse headache and opioid-induced hyperalgesia: A review of mechanisms, a neuroimmune hypothesis and a novel approach to treatment.

Author information

1
Discipline of Pharmacology, University of Adelaide, Australia. jacinta.johnson@adelaide.edu.au

Abstract

INTRODUCTION:

Patients with chronic headache who consume large amounts of analgesics are often encountered in clinical practice. Excessive intake of analgesics is now considered to be a cause, rather than simply a consequence, of frequent headaches, and as such the diagnosis "medication-overuse headache" (MOH) has been formulated. Despite the prevalence and clinical impact of MOH, the pathophysiology behind this disorder remains unclear and specific mechanism-based treatment options are lacking.

DISCUSSION:

Although most acute headache treatments have been alleged to cause MOH, here we conclude from the literature that opioids are a particularly problematic drug class consistently associated with worsening headache. MOH may not be a single entity, as each class of drug implicated may cause MOH via a different mechanism. Recent evidence indicates that chronic opioid administration may exacerbate pain in the long term by activating toll-like receptor-4 on glial cells, resulting in a pro-inflammatory state that manifests clinically as increased pain. Thus, from the available evidence it seems opioid-overuse headache is a phenomenon similar to opioid-induced hyperalgesia, which derives from a cumulative interaction between central sensitisation, due to repeated activation of nociceptive pathways by recurrent headaches, and pain facilitation due to glial activation.

CONCLUSION:

Treatment strategies directed at inhibiting glial activation may be of benefit alongside medication withdrawal in the management of MOH.

PMID:
23144180
DOI:
10.1177/0333102412467512
[Indexed for MEDLINE]

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