Il existe une littérature peu volumineuse encore sur l’efficacité de la méthadone comme opioïde employé dans le traitement de la douleur cancéreuse. Une revue systématique de la banque de données Cochrane sous la plume de Nicholson a été éditée pour la première fois en 2004 et mise à jour en 2007.
Je vous laisse le soin de lire les conclusions que je n’ai pas traduites.
On peut résumer en retenant qu’il n’y a que 9 études randomisées contrôlées et que ces études n’étaient pas standardisées et peu uniformisées. Par contre, efficacité et tolérabilité étaient semblables entre morphine et méthadone. On notait entre autres que la comparaison se faisait sur une courte période de temps, dose contre dose, alors qu’on sait très bien que la méthadone devient plus puissante avec l’usage.
La revue ne permet pas de constater une efficacité supérieure dans le cas de douleur neuropathique pour la méthadone autrement que de façon anecdotique.
Donc, comme à l’habitude, le recul n’est pas assez grand et le nombre d’études adéquates n’est pas encore assez important.
Revue Cochrane 2004, mise à jour 2007
"Main results
This updated review includes nine RCTs (six double blinded, two crossover) with 459 recruits and 392 completing patients. All studies involved active opioid comparators (morphine, dextromoramide, pethidine, diamorphine with cocaine mixture) with different dose and titration schedules and various pain scoring scales. One study differentiated cases by pain syndrome. Few presented complete pain data sets but complete adverse events data were recorded in every study. Efficacy and tolerability were broadly similar between methadone and morphine. No useful meta-analysis has been possible.
Authors' conclusions
The updated review contains new information supporting the previous conclusions that methadone has similar analgesic efficacy to morphine. The additional study examined neuropathic and non-neuropathic pain, finding no superiority for methadone in the former group.
The new study also addresses a clinically relevant concern about short term/single dose studies. Use beyond a few days may result in methadone accumulation leading to delayed onset of adverse effects. In an assessment over 28 days there was a higher rate of withdrawal due to side effects in the methadone group. This observation reinforces the advice that experienced clinicians should take responsibility for initiation and careful dose adjustment and monitoring of methadone."
Nicholson Alexander B. Methadone for cancer pain.*
Implications for practice
From the available evidence, methadone appears to be an effective analgesic in patients with cancer pain. However, there are significant differences between the manner of use of methadone in most of the included studies, and use of methadone in a clinical situation where repeated dosing over weeks or months is required. Anecdote suggests that methadone may be superior to other opioid analgesics in the treatment of cancer-related neuropathic pain.
Implications for research
The major problem with research involving methadone relates to its unique characteristics. Repeated dose studies using methadone at fixed dose intervals is potentially hazardous, making it impossible to conduct a randomized trial against an alternative opioid given regularly since blinding is not possible. Randomization between placebo and methadone for patients with cancer pain would be unacceptable to most clinicians.
Methadone for cancer pain; Alexander B Nicholson*