Drug-related information generates placebo and nocebo responses that modify the drug response.
OBJECTIVE
Administration of the muscle relaxant carisoprodol and placebo was crossed with information that was agonistic or antagonistic to the effect of carisoprodol. It was investigated whether information alone induced physiological and psychological responses, and whether information modified the response to the drug.


METHODS
Half of the subjects received capsules containing 525 mg carisoprodol together with information that the drug acted in a specific way (Groups Relaxant/C, Stimulant/C, and No Information/C). The other half of the subjects received lactose (Groups Relaxant/L, Stimulant/L, and No Information/L). Dependent variables were blink reflexes and skin conductance responses, subjective measures of tension and sleepiness, and serum carisoprodol and meprobamate concentrations. Recordings were made between 15 and 130 minutes after administration of the capsules.


RESULTS
The Stimulant/L group reported more tension compared with the other two groups, and carisoprodol increased tension even more in the Stimulant/C group. The Relaxant/C group displayed higher levels of carisoprodol serum concentration compared with the other groups that received carisoprodol.


CONCLUSIONS
Reported tension was modulated in the direction suggested by the stimulant information. The effect of carisoprodol on tension was also modulated by stimulant information. Increased carisoprodol absorption in the group that received relaxant information could be a mechanism in the placebo response.
Flaten
M A
MA
Department of Psychology, University of Tromsø, Norway. magne.flaten@svt.ntnu.no
Simonsen
T
T
Olsen
H
H
D000293:Adolescent; D000328:Adult; D001767:Blinking / Q000187:drug effects*; D002328:Carisoprodol / Q000097:blood / Q000494:pharmacology*; D003071:Cognition / Q000502:physiology*; D004311:Double-Blind Method; D004348:Drug Labeling; D004576:Electromyography; D005260:Female; D005712:Galvanic Skin Response / Q000187:drug effects*; D006801:Humans; D008297:Male; D009125:Muscle Relaxants, Central / Q000097:blood / Q000494:pharmacology*; D015990:Placebo Effect; D012890:Sleep; D013997:Time Factors; D014851:Wakefulness
D009125:Muscle Relaxants, Central; D002328:Carisoprodol