Chronic neuropathic pain is often refractory to standard pharmacological treatments. Although growing evidence supports the use of inhaled cannabis for neuropathic pain, the lack of standard inhaled dosing plays a major obstacle in cannabis becoming a "main stream" pharmacological treatment for neuropathic pain. The objective of this study was to explore the pharmacokinetics, safety, tolerability, efficacy, and ease of use of a novel portable thermal-metered-dose inhaler (tMDI) for cannabis in a cohort of eight patients suffering from chronic neuropathic pain and on a stable analgesic regimen including medicinal cannabis. In a single-dose, open-label study, patients inhaled a single 15.1 ± 0.1 mg dose of cannabis using the Syqe Inhaler device. Blood samples for Δ(9)-tetrahydrocannabinol (THC) and 11-hydroxy-Δ(9)-THC were taken at baseline and up to 120 minutes. Pain intensity (0-10 VAS), adverse events, and satisfaction score were monitored following the inhalation. A uniform pharmacokinetic profile was exhibited across all participants (Δ(9)-THC plasma Cmax ± SD was 38 ± 10 ng/mL, Tmax ± SD was 3 ± 1 minutes, AUC₀→infinity ± SD was 607 ± 200 ng·min/mL). Higher plasma Cmax increase per mg Δ(9)-THC administered (12.3 ng/mL/mg THC) and lower interindividual variability of Cmax (25.3%), compared with reported alternative modes of THC delivery, were measured. A significant 45% reduction in pain intensity was noted 20 minutes post inhalation (P = .001), turning back to baseline within 90 minutes. Tolerable, lightheadedness, lasting 15-30 minutes and requiring no intervention, was the only reported adverse event. This trial suggests the potential use of the Syqe Inhaler device as a smokeless delivery system of medicinal cannabis, producing a Δ(9)-THC pharmacokinetic profile with low interindividual variation of Cmax, achieving pharmaceutical standards for inhaled drugs.
Keywords: analgesia; inhalation; medicinal cannabis; neuropathic pain; pain; pharmacokinetics; vaporization; Δ9-THC.