To the Editor:
The article by Crosby et al. made for interesting and informative reading.
1
Their study appears to revalidate the safety and efficacy of intravenous magnesium therapy for neuropathic pain poorly responsive to opioids. In this context, we would like to draw attention to some additional data relevant to this subject.Tanaka and coworkers studied the effect of intravenous magnesium (0.5 mol.1-1) 5 ml bolus followed by an infusion of the same dose, once a week, in 8 patients suffering from neuropathic pain.
2
In 4 patients, the pain intensity visual analogue scale score decreased 3 points or more after therapy 3 to 11 times. While a heat sensation was felt by some of the patients after the bolus magnesium, no hemodynamic or other sever side effects were observed.While the authors mentioned the beneficial role of magnesium in postoperative analgesia, newer studies seem to have controversial results. Koinig et al., in a randomized double-blinded study, assessed the analgesic effect of perioperative magnesium sulfate in 46 patients undergoing arthroscopic knee surgery under general anesthesia.
3
Patients received either magnesium 50mg/kg preoperatively followed by 8mg/kg/hr or isotonic chloride. They found reduced intra- and postoperative analgesic requirements in patients with almost identical levels of surgical stimulation in the magnesium group (p < 0.01). In yet another prospective, randomized, double-blinded and placebo-controlled study involving 24 patients undergoing elective hysterectomy, patients received a 5-hour infusion of either placebo or magnesium laevulinate (initial bolus 8 mmol:then 8mmol/h) after induction of anesthesia.4
Patients in the magnesium group experienced more episodes of severe unbearable pain (16% vs. 6%, p=0.02), median pain scores were higher in the magnesium group 3 hours postoperatively (p=0.04), and cumulative morphine consumption was similar in the two groups after the first postoperative hour. They concluded that the use of magnesium was associated with short-term decreases in postoperative analgesia.The authors mention the useful analgesic effect of magnesium in migraine headaches. In a more recent study, the same group quoted by the authors evaulated the efficacy of intravenous magnesium to alleviate headaches of various types, including chronic migrainous headaches, chonic tension-type headaches and cluster headaches.
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Of 40 patients receiving 1 gram of magnesium sulfate, 32 (80%) had immediate pain relief (p < 0.005). They concluded that low serum brain tissue ionized magnesium levels might precipitate headache symptoms in susceptible patients, who may benefit from intravenous magnesium therapy.Other interesting new studies show the efficacy of magnesium in reducing pain associated with metastatic bone cancer
6
, primary dysmenorrhea7
and primary fibromyalgia syndrome.8
The above data, in conjunction with that presented by the authors, helps us to define more clearly the more recent therapeutic uses of magnesium in the alleviation of various pain syndromes.References
- Magnesium for cancer-related neuropathic pain.J Pain Symptom Manage. 2000; 19: 35-39
- Relief of neuropathic pain with intravenous magnesium.Masui-Japanese J Anesth. 1998; 47: 1109-1113
- Magnesium sulfate reduces intra- and postoperative analgesic requirements.Anesth Analg. 1998; 87: 206-210
- Perioperative magnesium infusion and postoperative pain.Acta Anesthesiol Scand. 1997; 41: 1023-1027
- Intravenous magnesium sulfate rapidly alleviates headaches of various types.Headache. 1996; 36: 154-160
- The efficacy of choline magnesium trisalicylate (CMT) in the management of metastatic bone pain:a pilot study.Palliative Medicine. 1994; 8: 129-135
- Therapeutic effects of magnesium in dysmenorrhea.Schweizerische Rundschau Fur Medizin Praxis. 1990; 79: 491-494
- Treatment of fibromylagia syndrome with Super-Malic; a randomized, double-blind, placebo-controlled crossover pilot study.J Rheumatol. 1995; 22: 953-958
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© 2000 U.S. Cancer Pain Relief Committee. Published by Elsevier Inc.
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