“In 1999, a report of the United States Institute of Medicine recommended further investigations of the possible benefits of cannabis (marijuana) as a medicinal agent for a variety of conditions, including neuropathic pain due to HIV distal sensory polyneuropathy (DSPN). The most abundant active ingredient in cannabis, tetrahydro-cannabinol (THC), and its synthetic derivatives, produce effective analgesia in most animal models of pain. The antinociceptive effects of THC are mediated through cannabinoid receptors (CB1, CB2) in the central and peripheral nervous systems, which in turn interact with noradrenergic and κ-opioid systems in the spinal cord to modulate the perception of painful stimuli. The endogenous ligand of CB1, anandamide, itself is an effective antinociceptive agent. In open-label clinical trials and one recent controlled trial, medicinal cannabis has shown preliminary efficacy in relieving neuropathic pain.”
“We conducted a clinical trial to assess the impact of smoked cannabis on neuropathic pain in HIV. This was a phase II, double-blind, placebo-controlled, crossover trial of analgesia with smoked cannabis in HIV-associated distal sensory predominant polyneuropathy (DSPN).”
“…pain relief was greater with cannabis than placebo…”
“Smoked cannabis was generally well tolerated and effective when added to concomitant analgesic therapy in patients with medically refractory pain due to HIV DSPN.”
“Our findings suggest that cannabinoid therapy may be an effective option for pain relief in patients with medically intractable pain due to HIV-associated DSPN.”
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3066045/