Morphine responsiveness in a group of well‐defined multiple sclerosis patients: A study with i.v. morphine

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.

Symptomatic Treatment of Multiple Sclerosis

“…If opioids are used in treatment escalation for central pain, high dosages are required in most cases [75] and will therefore not be tolerated by many on long-term treatment, e.g. morphine 9–30 mg/day (class II evidence [76]).…”

Mechanisms and Pharmacology of Neuropathic Pain in Multiple Sclerosis

“…Despite the widespread use of opioids for chronic pain, remarkably few studies have investigated their efficacy for the neuropathic pain of MS. A single dose using intravenous morphine decreased MS pain (>50% pain reduction) in 29% of the 14 patients involved in a single-blind non-randomized placebo-controlled trial (Kalman et al, 2002). Opioid receptors appear to mediate the analgesic effect of morphine, as it was reversed by naloxone.…”

Central Pain Syndromes

“…In MS patients the efficacy of opioids in CP has not been documented. In a nonrandomized, placebo-controlled study [48] it was found that IV morphine only had an analgesic effect in a minority (4/14) of the MS patients with central pain.…”

“…The same is true of opioids and tramadol, in which long-term side effects and drug addiction are concerns. Small studies in CP have failed to document an effect of opioids in stroke patients [16] and MS patients [48]. However, opioids as well as tramadol are effective in reducing peripheral neuropathic pain and may also be considered in refractory CP.…”