World Health Organization essential medicines lists: where are the drugs to treat neuropathic pain?


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1. IntroductionNeuropathic pain has been deemed a priority health issue5 and is the topic of the 2014 to 2015 Global Year Against Neuropathic Pain campaign of the International Association for the Study of Pain (http://www.iasp-pain.org/GlobalYear/NeuropathicPain). Between 6% and 10% of adults are affected by chronic pain with neuropathic features,6,24,26 and this prevalence is significantly greater among individuals with specific conditions. For example, neuropathic pain is a common comorbidity in infectious diseases such as HIV, leprosy, and herpes zoster, and in noninfectious conditions such as diabetes mellitus, stroke, multiple sclerosis, and traumatic limb and spinal cord injury.7,13,15,18,20 The pain is associated with significant decreases in quality of life and socioeconomic well-being, even more so than nonneuropathic chronic pain.9,19,21 Developing and emerging countries share the greatest burden of conditions that are associated with the development of neuropathic pain5,10 and can ill afford the negative consequences of this pain.There are medicines with proven efficacy in the treatment of neuropathic pain.11,12 Nevertheless, the pain can be difficult to treat, with significant interindividual variation in efficacy within and between drug classes, independent of the underlying peripheral or central nervous system lesion or disease.2,4 Effective management of neuropathic pain within a population therefore requires access to a small, but crucial, group of drug classes with proven efficacy.The World Health Organization's (WHO) model list of essential medicines (http://www.who.int/selection_medicines/list/en/) presents medicines deemed necessary to meet priority health needs, and local implementation of essential medicines policies is associated with improved quality use of medicines.14,17 However, none of the analgesic medicines included in the WHO model list is recommended as first-line treatments for neuropathic pain.11 Thus, the WHO model list is not a good framework from which national policies on managing neuropathic pain can be structured, but countries do adapt the model list according to local needs and resources.17 To estimate the nominal availability of medicines recommended for the treatment of neuropathic pain in developing and emerging countries, we assessed national essential medicines lists (NEMLs) for the inclusion of recommended treatments. We also assessed whether the coverage of recommended drugs classes on these NEMLs was dependent on countries' economic status.2. Methods2.1. National essential medicines list selectionWe confined our analysis to the 117 NEMLs accessible through the WHO Web site (http://www.who.int/selection_medicines/country_lists/en/). Updated editions of the 117 NEMLs were sought on public, crawler-based search engines using country names, and titles of the downloaded documents as search terms; 14 newer editions were identified.2.2. Data extractionEach NEML was independently reviewed by 2 authors. The NEMLs were assessed for drugs recently recommended as first or second-line treatments for neuropathic pain after a meta-analysis and grading of the evidence.11 Drug classes and drugs assessed included the following: (1) tricyclic antidepressants (TCA)—amitriptyline, nortriptyline, clomipramine, desipramine, and imipramine; (2) serotonin and noradrenaline reuptake inhibitors—duloxetine and venlafaxine; (3) anticonvulsants—gabapentin and pregabalin; (4) opioids—tramadol; and (5) topical agents—capsaicin and lidocaine. Drugs were recorded as being listed if they appeared anywhere on an NEML, irrespective of therapeutic class classification or treatment indications. Lidocaine was only recorded as being listed if it was specified as a topical formulation and at a concentration of at least 5%, or was a eutectic mix of 2.5% lidocaine: 2.5% prilocaine. Capsaicin was only recorded as being listed if the concentration was specified to be at least 8%. Information was also extracted on the strong opioids morphine, methadone, and oxycodone, which are listed in the WHO model list and are recommended as second or third-line therapy for neuropathic pain.

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