Cannabidiol treatment for refractory idiopathic epilepsy in dogs: A systematic review with risk of bias assessment.

We conducted a systematic literature review of randomised controlled trials (RCTs) on the use of cannabidiol (CBD) as a supplementary treatment for refractory idiopathic epilepsy in dogs. The objective was to summarise the efficacy and adverse effects of CBD treatment and assess the potential risk of bias in conducted studies, including an assessment of the effects thereof on the evaluation of CBD for clinical use. Studies were included in the review if they were RCTs comparing groups of dogs with refractory idiopathic epilepsy treated with CBD oil or placebo oil, respectively. The outcomes had to be efficacy and adverse effects of the treatment. English-language reports of studies published in any year were considered. A total of three studies were included in the review. All studies suggested a reduction in seizure frequency during CBD treatment, and all observed ataxia as an adverse effect of CBD treatment or a reason for withdrawal from the studies. Additionally, studies found increased levels of serum alkaline phosphatase (ALP) in dogs treated with CBD. Adverse effects included vomiting and diarrhoea, changes in appetite, behavioural changes and somnolence. The studies were characterised by a moderate to high risk of bias, which affected their validity and reliability. Based on the existing literature, it is not possible to draw conclusions concerning the efficacy and potential adverse effects of CBD as a supplementary treatment for refractory idiopathic epilepsy in dogs, and more high-quality studies are needed to evaluate clinical efficacy, the optimal treatment dose and adverse effects.