Pharmacokinetics, Safety, and Tolerability of a Medicinal Cannabis Formulation in Patients with Chronic Non-cancer Pain on Long-Term High Dose Opioid Analgesia: A Pilot Study

Introduction

This phase I open-label study examined pharmacokinetics, safety, and tolerability of escalating doses of a novel combination cannabinoid medication (1:1 tetrahydrocannabinol [THC]/cannabidiol [CBD]) in patients with chronic non-cancer pain (CNCP) on high dose opioid analgesia.

Methods

Nine people with CNCP and oral morphine equivalent daily dose of 60 mg or higher were recruited. Blood concentrations of THC, 11-hydroxytetrahydrocannabinol (OH-THC), 11-nor-9-carboxy-tetrahydrocannabinol (COOH-THC), and CBD were assayed weekly. Concentrations were measured after a single dose of 2.5 mg THC/2.5 mg CBD on day 1, and daily escalating doses up to a single dose of 12.5 mg THC/12.5 mg CBD on day 29. Follow-up was on day 36 after a 7-day washout. Secondary outcome data encompassed pain, mood, and sleep parameters.

Results

The parent compounds THC, and CBD, and metabolites OH-THC and COOH-THC were detected at most time points. In general, the concentration of all analytes increased until 2 h post-administration, decreasing to approximately pre-dose concentrations by 8 h. There was considerable inter- and intra-individual variability. The study medication was well tolerated. Eight participants reported at least one adverse event (AE), with a total of 62 AEs; most common were euphoric mood, headache, and agitation, none classified as severe. There was no significant change to pain severity self-ratings, nor use of pain medications. Improvements in pain interference scores, mood, and some sleep parameters were observed.

Conclusion

The THC/CBD formulation was tolerated well in a group of patients with CNCP. Between-participant variability supports personalized dosing and “start low–go slow” titration. To validate and quantify improvements in secondary efficacy outcomes a randomized placebo-controlled study is needed.