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Conrad Notes
a timely medical meeting newsletter
D. J. Hewitt, MD, Memorial Sloan Kettering Cancer Center (MSKCC), New York City, found dextromethorphan (DM), a widely-used cough preparation, adds to the analgesic effect of opioids. This placebo controlled study consisted of 18 outpatients. Doses of 30 or 60 mg DM four times daily enhanced the analgesic effect of patients on 20 to 135 mg morphine sulfate equivalent (MSE) per day. The data support further study with a starting dose of 60 mg QID.
Dose-Ranging Protocol The investigators followed a randomized, double blind, sequential block design (8 patients per block) comparing placebo, 30 mg, 60 mg and 120 mg DM taken four times daily for four days. Safety monitoring included pulse rate, respiration, and oxygen saturation on Day 1 after a single dose of DM or placebo. Pain intensity scores, analgesia experience, amount of MSE needed, and adverse effects were monitored daily on Day 2 to 5.
Safety of DM Dosing The study sample of 12 males and 6 females ranged in age from 31 to 73 years. Opioid treatment consisted of 20 to 135 mg MSE per day. None of the patients were hospitalized or receiving chemotherapy.

Patients found the added 30 mg and 60 mg DM doses to be safe and well-tolerated. Moderate adverse effects in two patients (disorientation, disequilibrium, dysphagia, and transient facial pallor) with 120 mg DM led to closing the study. Hewitt found the most common side effects at all DM doses to be sleepiness, dizziness, dry mouth, lightheadedness, and headache.

Added DM Analgesia DM antagonizes receptors for N-methyl-d-aspartate (NMDA), an important excitatory amino acid involved in pain transmission. Alone, DM produces analgesia in animal models and in patients with chronic neuropathic pain. The present study included 18 patients representing major pain types: neuropathic (9), nociceptive (4), and mixed (5).

DM significantly lowered morning pain intensity scores according to average values for Days 2-5 (p<0.05). Although not statistically significant, a tendency for DM analgesia could be seen in other measurements such as:

  • overall pain relief

  • categorical pain intensity vs DM dose

  • daily pain relief vs DM dose

The observed pain relief and pain intensity scores with DM are encouraging. According to Hewitt, a larger sample size would yield additional statistically significant results.

For professional correspondence, please contact Dr. Hewitt at: dhewitt@neuro.emory.edu

Eugene A. Conrad

Presented at American Pain Society Meeting on 15 Nov 1996
CONRAD NOTES, © November 1996 All Rights Reserved
Eugene A. Conrad, PhD, MPH / ISSN 1078 / posted 26-Dec-1996

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