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.