The effect of opioid blockade on nociceptive flexion reflex (NFR) activity and subjective pain ratings was examined in 151 healthy young men and women. Using a within-subjects design, NFR threshold was assessed on 2 days after administration of either placebo or a 50 mg dose of naltrexone. Electrocutaneous pain threshold and tolerance levels were measured after NFR threshold assessment on each day. Results indicated that administration of naltrexone was consistently associated with hypoalgesic responding. Specifically, participants exhibited lower levels of NFR activity and reported lower pain ratings for electrocutaneous stimulation delivered at pain threshold and tolerance levels following administration of naltrexone as compared to placebo. These findings indicate that opiate blockade using the current standard dose may elicit hypoalgesia. A potential moderating effect of dose of opiate-blockade medication and level of endogenous opioid activation should be carefully examined in future research.
Bibliographical noteFunding Information:
This work was supported by a grant from the National Institutes of Health (NHLBI R01 HL64794).
Copyright 2008 Elsevier B.V., All rights reserved.
- Nociceptive flexion reflex (NFR)
- Opiate blockade