Topical application of doxepin hydrochloride, capsaicin and a combination of both produces analgesia in chronic human neuropathic pain: a randomized, double-blind, placebo-controlled study.
OBJECTIVE
To assess the analgesic efficacy of topical administration of 3.3% doxepin hydrochloride, 0.025% capsaicin and a combination of 3. 3% doxepin and 0.025% capsaicin in human chronic neuropathic pain.


METHODS
A randomized, double-blind, placebo-controlled study of 200 consenting adult patients. Patients applied placebo, doxepin, capsaicin or doxepin/capsaicin cream daily for 4 weeks. Patients recorded on a daily basis overall pain, shooting, burning, paraesthesia and numbness using a 0-10 visual analogue scale during the week prior to cream application (baseline levels) and for the 4 week study period. Side-effects and desire to continue treatment were also recorded.


RESULTS
Overall pain was significantly reduced by doxepin, capsaicin and doxepin/capsaicin to a similar extent. The analgesia with doxepin/capsaicin was of more rapid onset. Capsaicin significantly reduced sensitivity and shooting pain. Burning pain was increased by doxepin and by capsaicin and to a lesser extent by doxepin/capsaicin. Side-effects were minor. One patient requested to continue placebo cream, 17 doxepin cream, 13 capsaicin and 9 the combination of doxepin and capsaicin.


CONCLUSIONS
Topical application of 3.3% doxepin, 0.025% capsaicin and 3.3% doxepin/0. 025% capsaicin produces analgesia of similar magnitude. The combination produces more rapid analgesia.
McCleane
G
G
Pain Clinic, Craigavon Area Hospital, 68 Lurgan Road, Craigavon, BT63QQ5, N. Ireland. Gary@mccleane.freeserve.co.uk
D000287:Administration, Topical; D000328:Adult; D000929:Antidepressive Agents, Tricyclic / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use*; D002211:Capsaicin / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use*; D002908:Chronic Disease; D004311:Double-Blind Method; D004316:Doxepin / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000188:drug therapy* / Q000209:etiology / Q000523:psychology; D010147:Pain Measurement; D010292:Paresthesia / Q000188:drug therapy; D010523:Peripheral Nervous System Diseases / Q000150:complications*
D000929:Antidepressive Agents, Tricyclic; D004316:Doxepin; D002211:Capsaicin