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Morphine responsiveness in a group of well-defined multiple sclerosis patients: a study with i.v. morphine
Sigga Kalman1, Anders Osterberg, Jan Sörensen
1Department of Anaesthesiology, University Hospital, S-581 85 Linköping, Sweden.
Abstract:
Pain in multiple sclerosis (MS) is more common than has previously been believed. About 28% of all MS patients suffer from central pain (CP), a pain that is difficult to treat. In the present study we have investigated the responsiveness of this pain to morphine. Fourteen opioid-free patients (eight woman and six men) with constant, non-fluctuating, long-lasting CP caused by MS were investigated. Placebo (normal saline), morphine and naloxone were given intravenously in a standardized manner. The study design was non-randomized, single blind and placebo controlled. Ten patients experienced less than 50% pain reduction by placebo and less than 50% pain reduction by morphine. Four patients were opioid responders, i.e. had minimal or no effect on pain by placebo, >50% pain reduction after morphine and >25% pain increase after naloxone, given intravenously following morphine. However, this response was obtained after high doses of morphine (43 mg, 47 mg, 50 mg and 25 mg; mean 41 mg). Thus, compared with nociceptive pain, only a minority of the patients with CP due to MS responded to morphine and only at high doses. The present results are in accord with experimental studies indicating that neuropathic pain is poorly responsive but not totally unresponsive to opioids. The results do not support the routine use of strong opioids in MS patients with CP.
Insights
Central pain (CP) in multiple sclerosis (MS) is difficult to treat. This study found that only a minority of MS patients with CP respond to high doses of morphine, suggesting strong opioids are not routinely recommended.
Area of Science:
- Neurology
- Pain Medicine
- Pharmacology
Background:
- Central pain (CP) affects approximately 28% of multiple sclerosis (MS) patients.
- CP associated with MS is often challenging to manage effectively.
- Investigating novel therapeutic targets for CP in MS is crucial.
Purpose of the Study:
- To evaluate the efficacy of morphine in treating central pain (CP) in patients with multiple sclerosis (MS).
- To determine the proportion of MS patients with CP who are opioid responders.
- To assess the optimal dosage and response patterns to morphine in this patient population.
Main Methods:
- A non-randomized, single-blind, placebo-controlled study.
- Fourteen opioid-naive MS patients with constant CP received intravenous placebo, morphine, and naloxone.
- Pain reduction was assessed, with opioid responders defined by specific criteria for morphine efficacy and naloxone reversal.
Main Results:
- Only four out of fourteen patients (28.6%) were classified as opioid responders.
- Opioid responders required high mean doses of morphine (41 mg) for significant pain reduction (>50%).
- Ten patients experienced less than 50% pain reduction with both placebo and morphine.
Conclusions:
- A minority of multiple sclerosis patients with central pain respond to morphine, and only at high doses.
- Neuropathic pain, like CP in MS, shows limited responsiveness to opioids.
- Routine use of strong opioids for central pain in MS patients is not supported by these findings.