Clinical Trial: The Analgesic Effect of Vaporized Cannabis on Neuropathic Pain in Spinal Cord Injury

May 18, 2011

Barth Wilsey, M.D. of the Uni­ver­sity of Cal­i­for­nia at Davis are cur­rently hold­ing clin­i­cal tri­als to deter­mine the pain-numbing effects of cannabis on peo­ple with spinal cord injuries. The Abstract reads:

The present study will be designed to eval­u­ate the anal­gesic effects of vapor­ized cannabis in patients with neu­ro­pathic pain due to spinal cord injury. A within-subject crossover study of the effects of cannabis (3.5% and 1.7%) ver­sus placebo on spon­ta­neous and evoked pain will be per­formed. Both pain inten­sity and pain unpleas­ant­ness will be assessed to see if mar­i­juana affects sensory-discriminative pain more or less than the motivational-affective com­po­nent. If present, areas of mechan­i­cal allo­dy­nia will be assessed with repeated test­ing to deter­mine the degree of the allo­dy­nia regres­sion (if any) after inhal­ing cannabis via a vapor­izer. Heat evoked pain will be stud­ied using mild to mod­er­ately painful heat stim­uli deliv­ered to the painful area of the subject’s body using an elec­tron­i­cally con­trolled Peltier con­tact ther­mode via the Medoc TSA 2001 quan­ti­ta­tive sen­sory tester. Neu­ropsy­cho­log­i­cal func­tion­ing (atten­tion, learn­ing and mem­ory, and psy­chomo­tor per­for­mance) will be eval­u­ated with the Digit Sym­bol Modal­i­ties Test, the Hop­kins Ver­bal Learn­ing Test and the Grooved Peg­board Test before and after the admin­is­tra­tion of vapor­ized cannabis. The degree of antinoci­cep­tion will then be com­pared with neu­ropsy­cho­log­i­cal effects of cannabis for a syn­op­sis of the rel­a­tive effec­tive­ness (effi­cacy ver­sus side-effects) of the doses employed.

The hypoth­e­sis will be that vapor­ized cannabis can induce dose depen­dent antinoci­cep­tive changes in spon­ta­neous and evoked pain in sub­jects with neu­ro­pathic pain. The sec­ond hypoth­e­sis will be that the higher dose employed induce a greater degree of antinoci­cep­tion that is not inde­pen­dent of dif­fer­ences in mood, cog­ni­tion and psy­chomo­tor per­for­mance. Finally, it is hypoth­e­sized that an inter­ac­tion with time will occur such that antinoci­cep­tion will out­last changes in cog­ni­tive impair­ment and psy­chomo­tor performance.

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