Hj. Mcquay et al., DEXTROMETHORPHAN FOR THE TREATMENT OF NEUROPATHIC PAIN - A DOUBLE-BLIND RANDOMIZED CONTROLLED CROSSOVER TRIAL WITH INTEGRAL N-OF-1 DESIGN, Pain, 59(1), 1994, pp. 127-133
The aim was to compare the analgesic effectiveness and adverse effect
incidence of oral dextromethorphan (DM) with placebo in patients with
neuropathic pain. The first 10-day treatment period was a multiple-dos
e double-blind randomised controlled cross-over comparison of 13.5 mg
of DM 3 times a day (t.d.s.) with placebo t.d.s.: 5 treatment pairs, e
ach pair 1 day DM and 1 day placebo. The second 10-day treatment perio
d used 27 mg of DM t.d.s. vs, placebo, with the same design. The study
incorporated a 5 pair n-of-1 design for each of the 2 doses of DM. Pa
tients took the study medication in addition to any pre-existing analg
esic regime. Patients who reported benefit could continue with DM afte
r the study. Nineteen patients with chronic neuropathic pain were stud
ied over two 10-day treatment periods. Outcome measures were pain inte
nsity, pain relief, adverse effects, mood, sleep and global rating of
treatment. These were recorded by daily patient diaries and by clinic
assessments before and after each treatment period. There were no sign
ificant differences between DM and placebo on any of the clinic assess
ment outcome measures. Two patients had significantly better analgesia
on more than one outcome measure on within-patient testing. One had b
etter analgesia with DM. The other had better analgesia with placebo.
Ten patients had no adverse effects on either dose of DM. Two patients
withdrew during the first treatment period because of adverse effects
(which included increased pain intensity), and 5 during the second pe
riod. Five patients continued with DM after the study for 1-3 months.
No long-term clinical benefit was apparent in those who continued with
open DM. Dextromethorphan at either 40.5 or 81 mg daily did not relie
ve neuropathic pain.