Neuropathic pain is a chronic and potentially debilitating condition. Despite the availability of multiple treatment options, many produce only partial relief. As previous studies have demonstrated analgesic effects of the endocannabinoids, this study was designed to determine whether a nasal spray containing delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) could impact neuropathic pain.

This study included 380 patients with peripheral neuropathic pain associated with diabetes, or allodynia. The subjects were randomized to a control group or a treatment group. The treatment group received 2.7 mg of THC and 2.5 mg of CBD, administered at a maximum of 24 times every 24 hours. The outcome was measured by change in pain severity on a numerical rating scale (NRS). Secondary outcome measures included scores on a neuropathic pain scale, sleep quality, intoxication, subjective global impressions of change and quality of life.

All patients improved on the NRS pain scale over the initial weeks of treatment. The mean numeric rating scale score decreased from 6.9 at baseline to 4.2 at the end of the study. Improvements in the neuropathic pain scores were observed after four weeks of treatment, and were maintained over the nine months of the study, without an associated increase in the daily dose of the spray. After nine months, the majority of patients reported 30% or more improvement in pain scores compared to baseline. In addition, improvements in the secondary outcome measures of neuropathic pain scale scores, quality of life and sleep quality were positive and were maintained throughout the duration of the study.

This open label study found that patients with neuropathic pain can respond well, and over a long period of time, to a delta-9-tetrahydrocannabinol/cannab-idiol oral mucosal spray.