Medical cannabis oil for benign essential blepharospasm: a prospective, randomized controlled pilot study

Objective: To examine the efficacy and safety of medical cannabis in benign essential blepharospasm (BEB). Methods: This is a prospective, double-blind, placebo-controlled study. All consecutive adult BEB patients who had been treated with BTX-A injections without success between 3/2019 and 2/2020 were recruited. The study patients were randomly allocated into a treatment and a control (placebo) group in a 1:1 ratio. The treatment group used cannabis drops and the control group used cannabis oil drops during the first 6 weeks of the study, and both groups were treated with the medical cannabis drops during the second 6 weeks. The cannabis dose was gradually increased for each patient depending upon effect and tolerability. Results: Three patients were included in each group (treatment and control groups). The mean duration of spasm attack during the first 6 weeks was 4.29 min in the treatment group and 73.9 min in the placebo group (P < 0.01). During the last 6 weeks, the treatment group used an average of 6.27 drops and the placebo group used an average of 5.36 drops (P = 0.478). There were 61 spasm events in the treatment group and 94 spasm events in the placebo group (P = 0.05). The mean duration of spasm attack was 1.77 and 8.96 min, respectively (P < 0.01). The side effects were mild, and they included general fatigue, dry mouth, and insomnia. Conclusions: Medical cannabis can be an effective and safe treatment for BEB as a second line after BTX-A injections when used for 3 months. No significant ocular or systemic side effects was associated with the treatment.