Cannabis Research Publishing

CONTEXT: 1',1'dimethylheptyl-Delta8-tetrahydrocannabinol-11-oic acid (CT-3), a
potent analog of THC-11-oic acid, produces marked antiallodynic and analgesic
effects in animals without evoking the typical effects described in models of
cannabinoids. Therefore, CT-3 may be an effective analgesic for poorly
controlled resistant neuropathic pain. OBJECTIVE: To examine the analgesic
efficacy and safety of CT-3 in chronic neuropathic pain in humans. DESIGN AND
SETTING: Randomized, placebo-controlled, double-blind crossover trial conducted
in Germany from May-September 2002. PARTICIPANTS: Twenty-one patients (8 women
and 13 men) aged 29 to 65 years (mean, 51 years) who had a clinical presentation
and examination consistent with chronic neuropathic pain (for at least 6 months)
with hyperalgesia (n = 21) and allodynia (n = 7). INTERVENTIONS: Patients were
randomized to two 7-day treatment orders in a crossover design. Two daily doses
of CT-3 (four 10-mg capsules per day) or identical placebo capsules were given
during the first 4 days and 8 capsules per day were given in 2 daily doses in
the following 3 days. After a washout and baseline period of 1 week each,
patients crossed over to the second 7-day treatment period. MAIN OUTCOME
MEASURES: Visual analog scale (VAS) and verbal rating scale scores for pain;
vital sign, hematologic and blood chemistry, and electrocardiogram measurements;
scores on the Trail-Making Test and the Addiction Research Center
Inventory-Marijuana scale; and adverse effects. RESULTS: The mean differences
over time for the VAS values in the CT-3-placebo sequence measured 3 hours after
intake of study drug differed significantly from those in the placebo-CT-3
sequence (mean [SD], -11.54 [14.16] vs 9.86 [21.43]; P =.02). Eight hours after
intake of the drug, the pain scale differences between groups were less marked.
No dose response was observed. Adverse effects, mainly transient dry mouth and
tiredness, were reported significantly more often during CT-3 treatment (mean
[SD] difference, -0.67 [0.50] for CT-3-placebo sequence vs 0.10 [0.74] for
placebo-CT-3 sequence; P =.02). There were no significant differences with
respect to vital signs, blood tests, electrocardiogram, Trail-Making Test, and
Addiction Research Center Inventory-Marijuana scale. No carryover or period
effects were observed except on the Trail-Making Test. CONCLUSIONS: In this
preliminary study, CT-3 was effective in reducing chronic neuropathic pain
compared with placebo. No major adverse effects were observed.

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