A multicentre, open-label, follow-on study to assess the long-term maintenance of effect, tolerance and safety of THC/CBD oromucosal spray in the management of neuropathic pain


Peripheral neuropathic pain (PNP) poses a significant clinical challenge. The long-term efficacy of delta-9-tetrahydrocannabinol (THC)/cannabidiol (CBD) oromucosal spray was investigated in this 38-week open-label extension study. In total, 380 patients with PNP associated with diabetes or allodynia entered this study from two parent randomised, controlled trials. Patients received THC/CBD spray for a further 38 weeks in addition to their current analgesic therapy. Neuropathic pain severity was the primary efficacy measure using a pain 0–10 numerical rating scale (NRS). Additional efficacy, safety and tolerability outcomes were also investigated. In total, 234 patients completed the study (62 %). The pain NRS showed a decrease in score over time in patients from a mean of 6.9 points (baseline in the parent studies) to a mean of 4.2 points (end of open-label follow-up). The proportion of patients who reported at least a clinically relevant 30 % improvement in pain continued to increase with time (up to 9 months); at least half of all patients reported a 30 % improvement at all time points. Improvements were observed for all secondary efficacy outcomes, including sleep quality 0–10 NRS scores, neuropathic pain scale scores, subject global impression of change and EQ-5D questionnaire scores. THC/CBD spray was well tolerated for the study duration and patients did not seek to increase their dose with time, with no new safety concerns arising from long-term use. In this previously difficult to manage patient population, THC/CBD spray was beneficial for the majority of patients with PNP associated with diabetes or allodynia.

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Conflicts of interest

B. Hoggart, S. Ratcliffe, E. Ehler, K. H. Simpson, J. Hovorka, J. Lejčko and M. Serpell were all investigators in this study and received investigator fees from GW Pharma Ltd. accordingly for their participation in the study. GW Medical Writers L. Taylor, H. Lauder and S. M. Greenwood undertook the initial compilation and quality control review of the manuscript. Together with the other authors, the target journal was then agreed and all authors reviewed and contributed to the content of the manuscript and agreed upon the final submitted version. All intellectual property rights arising out of the current clinical study are vested in or exclusively licenced to GW.

Ethical standards

The study was approved by the Institutional Review Boards or Ethical Committees in each of the countries in which it was run and was conducted in accordance with the principles of the Declaration of Helsinki and the International Conference on Harmonisation Good Clinical Practice guidelines.

Informed consent

All patients gave informed consent prior to their inclusion in the study and before any study-related procedures were carried out.

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Correspondence to B. Hoggart.

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Hoggart, B., Ratcliffe, S., Ehler, E. et al. A multicentre, open-label, follow-on study to assess the long-term maintenance of effect, tolerance and safety of THC/CBD oromucosal spray in the management of neuropathic pain. J Neurol 262, 27–40 (2015). https://doi.org/10.1007/s00415-014-7502-9

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  • Cannabidiol
  • Cannabinoid
  • Delta-9-tetrahydrocannabinol
  • Neuropathic pain
  • THC/CBD spray