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Drug interactions with CBD

Tapley, P & Kellett, S 2019, ‘Cannabis-based medicines and the perioperative physician’, Perioperative Medicine, vol 8, pp 19

  • literature review re interactions of CBD and THC with relevant drugs of clinical relevance

  • most drug interactions were with THC administration (not relevant in Australia.

  • relevant interactions with CBD are:

Induction agents

  • A cannabis extract premedication in dogs resulted in quicker onset and longer lasting anaesthesia with propofol



  • Animal studies show cannabinoids and opioids are synergistic, with the analgesic efficacy of cannabinoids not reduced when opioid antagonists are administered.



  • Ketamine induces endogenous cannabinoid release, which may partially explain its role in anti-nociception.

  • The psychomotor side effects of ketamine are enhanced with CBD administration, but no adverse behavioural or cardiovascular effects have been noted.



  • The gabapentinoids and cannabinoids have overlapping pharmacological actions, with increased therapeutic and side effects when combination dosing is used

  • Gabapentin’s mechanism of action is via α2δ subunits on voltage-dependent calcium channels, with reduction in neural transmission. Similarly, activation of the CB receptor results in inhibition of the voltage dependent calcium channel.


Santisteban, RR, Betancur, JJ, Muñoz, LC, Libreros, P & Cristancho, D 2021, ‘Preoperative administration of cannabidiol (CBD) in healthy dogs undergoing elective surgery in Colombia: 16 Cases’, Research Abstract Program of the 2021 ACVIM Forum, Journal of Veterinary Internal Medicine, vol. 35, no . 6, pp. 2943-3079



Aim: to retrospectively review the effect of a single dose administration of two pharmaceutical grade CBD oils on basic cardiorespiratory parameters and anaesthetic recovery of dogs undergoing elective surgery.


Sample:  16 healthy dogs, part of the spay/neuter program at University of Santa Rosa, Columbia ( 11 females, 3 male dogs with a median age of 4,4 years (range 0,5-9 years)). Complete medical and anaesthesia records were reviewed.


Intervention: Dogs were randomly given either (1) a full spectrum cannabis oil with 200 mg/ml and THC up to 1 mg/ml (THC:CBD 1:20 ratio); OR (2) CBD only oil (100 mg/ml). 

  • Dogs were given was 2 mg/kg dose orally, 1 hour before any anaesthetic premedication and closely monitored.

  • Premed - meloxicam, tramadol + xylazine

  • Induced and maintained with ether ketamine and/or propofol

  • Basic monitoring of heart rate, respiratory rate, pulse, rectal temperature during surgery and recovery


Relevant findings:

  • None of the dogs experience adverse effects during the first hour of observation.

  • Of the 7 dogs that received THC:CBD ratio 1:20, no anaesthesia complication was observed during surgery.

  • Of the 9 dogs that received CBD only, only one dog experienced epileptiform activity during anaesthetic induction.  Epileptiform activity observed was attributable to concurrent medication

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