Caffeine does not attenuate experimentally induced ischemic pain in healthy subjects.
OBJECTIVE
Caffeine is likely the most widely used psychoactive substance in the world. It is also an analgesic adjuvant and has individual analgesic properties. The latter effect has been attributed to adenosine receptor antagonism, but the site of action is unknown. The aim of this study was to investigate the analgesic properties of caffeine on experimentally induced ischemic pain and to attempt to elucidate whether the site of action is central or peripheral.


METHODS
Seventeen healthy subjects received intravenous (i.v.) regional and systemic infusions of caffeine at 10 mg/kg or placebo in a double-blind, crossover fashion to investigate the site of action for caffeine-induced analgesia. Subjects underwent a sub-maximum effort tourniquet test. Pain scores [visual analogue scale (VAS), 0-100] were assessed every minute up to a maximum of 45 min.


RESULTS
The sum of pain scores (SPS, accumulation of VAS scores) was attenuated neither by systemic 2405 (+/-234) nor by i.v. regional caffeine 2427 (+/-190) as compared with placebo 2442 (+/-205), P=0.99 (mean+/-SEM). Time to maximal VAS score did not differ significantly between treatments, P=0.94. There was no correlation between caffeine concentration in plasma and time to maximal pain score, or between SPS and plasma concentration.


CONCLUSIONS
Caffeine does not have an analgesic effect on ischemic pain, either by a peripheral or by a central site of action.
Dellermalm
J
J
Department for Clinical Science, Intervention and Technology, Division of Anesthesiology, Karolinska Institutet at Karolinska University Hospital, Huddinge, Stockholm, Sweden.
Segerdahl
M
M
Grass
S
S
D000328:Adult; D000700:Analgesics / Q000008:administration & dosage* / Q000097:blood; D002110:Caffeine / Q000008:administration & dosage* / Q000097:blood; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000188:drug therapy*; D010147:Pain Measurement; D016896:Treatment Outcome; D055815:Young Adult
D000700:Analgesics; D002110:Caffeine