INTRODUCTION: The use of cannabis as medical therapy to treat chronic pain and spasticity in patients with multiple sclerosis (MS) is increasing. However, the evidence on safety when initiating treatment with medical cannabis oils is limited. The aim of this study was to investigate the safety of sublingual medical cannabis oils in patients with MS.

METHODS: In this prospective observational safety study 28 patients with MS were treated with medical cannabis oils (THC-rich, CBD-rich and THC+CBD combined products) and were followed during a titration period of four weeks. Patients were evaluated at treatment start (Visit 1) and after four weeks treatment (Visit 2). At each visit neurological examination (Expanded Disability Status Scale - EDSS), ambulation (Timed 25-Foot Walk Test - T25FWT), routine blood tests, plasma cannabinoids, dexterity (9-Hole Peg Test - 9-HPT) and processing speed (Symbol Digit Modalities Test - SDMT) were tested. Adverse events (AEs) and tolerability were reported at Visit 2. Secondary, efficacy of medical cannabis on pain, spasticity and sleep disturbances were measured by numeric rating scale (NRS-11) each day during the 4-week treatment period.

RESULTS: During treatment with cannabis preparations containing 10-25 mg/mL THC, the most common AEs were dry mouth, drowsiness, dizziness and nausea of mild to moderate degree. Two patients experienced pronounced symptoms with excessive dreaming and drowsiness, respectively, which led to treatment stop during the titration. Three serious adverse events (SAE) were reported but were not associated with the treatment. Mean doses of THC and CBD were 4.0 mg and 7.0 mg, respectively, and primarily administered as a once-daily evening dose. Furthermore, pain decreased from a median NRS score of 7 to 4, (p = 0.01), spasticity decreased from a median NRS score of 6 to 2.5 (p = 0.01) and sleep disturbances decreased from a median NRS score of 7 to 3 (p < 0.001). No impairment in disability, ambulation, dexterity or processing speed was observed.

CONCLUSION: Treatment with medical cannabis oils was safe and well tolerated, and resulted in a reduction in pain intensity, spasticity and sleep disturbances in MS patients. This suggests that medical cannabis oils can be used safely, especially at relatively low doses and with slow titration, as an alternative to treat MS-related symptoms when conventional therapy is inadequate.