The use, by its sufferers, of cannabis-based agents to treat IBS has eventuated in large part due to the unfortunate fact that conventional treatment with anticholinergics, opioids, and antidepressants has been quite suboptimal, while three dedicated agents have been withdrawn from certain markets after prior regulatory approval.
The authors observed that the increased TRPV1 nerve fibers may contribute to visceral hypersensitivity and pain in IBS and provide a novel therapeutic target.
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Genetic variation affecting endocannabinoid metabolism was observed in diarrhea-predominant IBS patients. They observed that CB1 receptor-related mechanisms modify colonic transit and sensation and may influence the development of symptoms in Caucasian patients with IBS, particularly IBS-D. Unfortunately, while many patient surveys have touted benefits of cannabinoid treatment of IBS symptoms and abundant anecdotal support is evident on the Internet, little actual clinical work has been accomplished.
In 2016 156 of the microbiome-gut-brain axis in IBS is underscored by the recent finding that THC altered the microfloral balance in obese diet-induced obese mice, affecting the Firmicutes: Bacteroidetes ratio and preventing its increase or weight gain despite a high-fat diet. Thus, optimal gut health without pain and with the maintenance of appropriate body weight seems to require a complex interplay between diet, enteric flora, and endocannabinoid balance.
In a randomized controlled trial of 52 normal or healthy patients taking single doses of 7.5 mg of THC versus placebo, the drug increased colonic compliance and inhibited postprandial colonic tone and fasting and postprandial phasic pressure, with a trend toward relaxation of fasting colon tone.
Another study focused on visceral sensitivity to rectal distention as measured by a barostat in normal versus IBS patients after administration of THC.33 No significant differences were noted, but adverse events were reported in 100% of participants at the 10 mg dosage.