Efficacy Study of Nabilone in the Treatment of Diabetic Peripheral Neuropathic Pain
Status:
Unknown status
Trial end date:
2011-04-01
Target enrollment:
Participant gender:
Summary
Neuropathic pain occurs as a result of damage or disease of the peripheral or central nervous
system. Regardless of its cause, neuropathic pain (NeP) leads to a characteristic clinical
picture characterized by ongoing pain with steady or dysesthetic pain, such as burning or
aching, and paroxysmal pain such as shooting or stabbing. In conditions such as diabetic
neuropathy, changes in the membrane-bound proteins that form ion channels may alter the
electrical properties of the injured neuron, called remodeling. The net effect of membrane
remodeling is greater excitability of neurons, leading to a tendency towards action potential
generation and propagation in injured primary sensory neurons which occurs in the context of
nerve injury and disease. Over the past decade, a new endogenous cannabinoid
receptor-mediated system within the nervous system and upon immune-mediated cells has been
described. The cannabinoid receptor system consists of two receptors, CB1 and CB2 receptors,
as well as endogenously produced endocannabinoids which agonize these receptors.
This is a multicenter trial amongst Western Canadian sites to compare the efficacy of
nabilone versus placebo in treating patients with chronic neuropathic pain (NeP) due to
diabetic peripheral neuropathy (DPN).
A one-week screening period will occur, during which pain scores and sleep scores will be
tabulated. Following screening, a 4-week period of single blind treatment with flexible
dosing of nabilone at 0.5 - 4 mg/day will initiate. All subjects will begin with nabilone
therapy of 1 mg daily for a minimum of 4 days, with the dose of the study medication assessed
and adjusted either upwards or downwards as needed to balance efficacy for pain control with
tolerability of possible side effects. All subjects who experience at least a 30% reduction
in their weekly mean pain score during the single blind flexible dosing phase will be
considered a responder, and will be further continued in the study. During the double-blind
portion of the study, subjects randomized to nabilone will continue on the dose of nabilone
achieved at the completion of the single-blind phase, and this dose will be maintained
throughout the double-blind phase. Subjects randomized to placebo will receive 1 mg of
nabilone daily for one week, followed by 4 consecutive weeks of placebo. This dose of
nabilone will permit a tapering for those subjects achieving a higher daily dose of nabilone
during the single-blind phase, or will maintain those who were taking only 1 mg per day in
the single-blind phase, preventing an abrupt termination of treatment in subjects who are
randomized into the placebo portion of the study.