Cannabidiol interactions with oxycodone analgesia in an operant orofacial cutaneous thermal pain assay following oral administration in rats

Abstract

Previous studies have driven the notion that the cannabis constituent cannabidiol could be an effective adjunct to opioid administration for managing pain. Most of these studies have used experimental rodents with routes of administration, such as subcutaneous and intraperitoneal, that do not correspond with the routes used in clinical practice. In response to this, we tested the ability of cannabidiol co-administration to augment opioid analgesia via the more clinically-relevant oral route of administration. To this end, male and female rats were orally gavaged with cannabidiol (25 mg/kg), oxycodone (1.4 mg/kg), or a combination of both, after which they were tested in an operant thermal orofacial pain assay in which they voluntarily exposed their faces to cutaneous thermal pain to receive a palatable reward. All three drug conditions produced analgesic effects of varying degrees, being most profound in the combination group where a statistically significant enhancement over oxycodone-induced analgesia alone was evident. Additionally, oxycodone administration decreased lick frequencies - a measure of motor coordination of rhythmic movements - which too was magnified by co-administration of cannabidiol. Together these studies provide further support of an ability of cannabidiol to augment opioid effects, particularly analgesia, when administered by a route relevant to human pain management. As such, they encourage the notion that cannabidiol could find utility as an opioid-sparing approach to treating pain.

Keywords: Cannabidiol; Cannabinoid; Licking; Opioid; Oxycodone; Pain; Rat.