Chronic neuropathic pain is mainly treated with medications. These include antidepressants, antiepileptics, opioids, and topical local anaesthetics. Sometimes better pain relief is needed. Cannabinoids are known to have analgesic properties. The authors of the study evaluated the effect of a medication called Sativex. Sativex is made from selected strains of cannabis plants. It contains a combination of delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) in a spray form. The spray is used under the tongue or inside the cheek. Cannabinoids are thought to work at two types of receptors. CBD was used as combining it with THC is thought to lead to an increase in desired effects such as analgesia and sedation as well as decrease unwanted side effects.
125 subjects with neuropathic pain of peripheral origin were included in the study. 63 recieved the Sativex and 62 were on placebo. The authors wanted to study the medication effect on severity of pain, allodynia, sleep disturbance, mental distress and disability. The study lasted five weeks. They subjects were allowed to titrate the medication as they desired after the first seven to ten days. During this time, the number of sprays were limited and signs and symptoms of intoxication were monitored.
The improvement in pain over placebo was evident from the second week after titration until the end of the five week trial. 26 percent of the Sativex group reported greater than 30 percent improvement in pain compared to 15 percent of the placebo group. Improvenent in sleep, allodynia, and disability were also significantly improved over the placebo group. Doses remained stable after the two week titration period. The participants that chose to continue the study for up to 52 weeks did not need to significantly increase the number of sprays per day used.
Most common adverse side effects in the subjects using Sativex included nausea, vomiting, diarrhea, and constipaton. Another subject experienced paranoid thinking. 18 percent of the Sativex subjects withdrew from the study because of adverse events compared to three percent in the placebo group.
The authors concluded that Sativex has a positive effect in neuropathic pain. However, side effects, particularly involving the gastrointestinal tract may limit its use in some individuals.