European journal of pain : EJP
-
The rodent acidic saline model of hyperalgesia uses repeat injections of acidic saline in the right lateral gastrocnemius muscle, spaced five days apart, to induce a persistent decrease in hindpaw withdrawal thresholds. The objective of this study was to determine if alternate injection sites would permit development of hyperalgesia. ⋯ These data indicate that anatomically diverse peripheral stimuli can converge within the central nervous system to produce hyperalgesia.
-
Randomized Controlled Trial
Sex differences in analgesic response to ibuprofen are influenced by expectancy: a randomized, crossover, balanced placebo-designed study.
To determine whether there is a sex difference in placebo and ibuprofen analgesia expectancy. ⋯ We found no sex difference in baseline pain threshold or tolerance levels. When partitioned by sex and expectancy state, analgesia only occurred in males during positive expectancy states at 2, 3 and 4 h post-placebo, and at 1 and 2 h post-ibuprofen. The time course of analgesic action in males was as expected considering the pharmacokinetic profile of ibuprofen. Our study found that dosages of 800 mg of ibuprofen are ineffective in producing analgesia in women regardless of their expectations. We hypothesize that ibuprofen analgesia is produced by a combination of specific pharmacological effects and a non-specific beta endorphin-mediated placebo effect. Whatever the mechanism responsible for the analgesic response seen in males, this research re-emphasizes the importance of psychological factors in determining drug response. It also shows that these factors can differ between men and women, and thus the contribution of psychological factors on analgesia needs to be seriously re-evaluated.
-
The analgesic properties and mechanisms of loperamide hydrochloride, a peripherally acting opioid receptor agonist, in neuropathic pain warrant further investigation. ⋯ These findings suggest that both systemic and local administration of loperamide induce an opioid receptor-dependent inhibition of heat and mechanical hyperalgesia in nerve-injured rats, but that local paw administration of loperamide also induces thermal and mechanical antinociception.