Efficacy of Cannabidiol in Knee Osteoarthritis

Painful symptomatic osteoarthritis (OA) of the knee is a very common disease, especially in older people (lifetime prevalence 9.5%). Current systemic pharmacological treatment options are limited. The Osteoarthritis Research Society International recommends paracetamol, duloxetine, oral non-selective non-steroidal anti-inflammatory drugs and oral COX-2 inhibitors (anti-inflammatory substances) in patients without relevant concomitant diseases. In individuals with relevant concomitant diseases (diabetes, advanced age, high blood pressure, cardiovascular diseases, renal failure, gastrointestinal complications, depression, obesity), the recommendation for paracetamol, oral non-selective non-steroidal anti-inflammatory drugs and oral COX-2 inhibitors changes to 'inappropriate'.

In individuals with high co-morbidity risk (history of GI-bleeding, myocardial infarction, chronic renal failure) NSAIDs and oral COX-2 inhibitors are evaluated as inappropriate.

Many patients presenting with knee osteoarthritis are of an advanced age and suffer from various co-morbidities. The benefit of the available systemic pharmacological treatment options in these patients can be summarized as uncertain. Therefore, the investigation of new symptomatic systemic pharmacological treatment options for knee OA is relevant. Even in patients without known contraindications, the treatment period with non-steroidal anti-inflammatory drugs should be kept short. It follows that the investigation of new potentially anti-inflammatory substances is of interest in symptomatic OA of the knee.

Design

The planned study will be randomised, double-blind and placebo-controlled. 2 parallel groups will be investigated. One group will receive placebo, the other will receive 600mg cannabidiol per os during the treatment phase. The total study duration will be 13 weeks (2 weeks screening;

1 week titration phase; 7 weeks maintenance phase; 1 week tapering phase; 2 weeks follow-up) Main objective of the study will be to compare the change in the Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC) Pain Index from baseline to the last week of the maintenance phase between the placebo and verum groups. The WOMAC Osteoarthritis Index is a validated patient questionnaire to assess symptoms and physical functional limitations in everyday life.

Secondary objectives include comparing the change in the WOMAC Function Index, the Global Patient Assessment of Gonarthrosis and the VAS Score. The planned number of participants is 86 (43 patients per group)

Measures/procedure After a 2-week screening phase, patients are randomised to a 1:1 placebo:verum after written consent. During the screening all patients are adjusted to a basic medication of 3 times 1g paracetamol/day. In the cannabidiol arm, titration is carried out within one week to the target dose of 600mg per day. This dosage is maintained for 7 weeks. This is followed by a balancing phase of 1 week. A follow-up is carried out 2 weeks after the maintenance phase is finished.

4 study visits are associated with blood sampling (safety laboratory) and physical examination and the completion of questionnaires and are carried out at our pain outpatient clinic. The remaining weekly visits are carried out by telephone.

During the entire duration of the study, patients are allowed the rescue medication of Tramadol 50mg up to 6/day.