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The Medical Use of Marijuana in Inflammatory Bowel Disease
Gerich et al. recently summarized the data supporting the use of marijuana for digestive disorders (1). The authors' tentative positive attitude to clinical use of marijuana is based on published evidence from patients with gastrointestinal disorders that self medicate with marijuana and on the clinical trials published so far. However, the authors emphasize that at present the clinical data is limited and hence 'clinical efficacy of marijuana or its constituent phytochemicals for digestive disorders remains unclear'. This module will review the rationale for the use of cannabis in the treatment of inflammatory bowel disease (IBD) and the available clinical evidence for the use of cannabis in treatment of IBD and associated symptoms.
Izzo et al. have discussed the presence of cannabinoid receptors on neurons and nerve fibers throughout the enteric system including liver, pancreas, stomach, and the small and large intestines (2, 3). CB1 receptors were found both on the normal and inflamed human colonic epithelium. Both CB1 and CB2 receptors were found in macrophages and plasma cells in the human colon. The pharmacological actions of cannabis include anti-inflammatory effects, and decreased gastrointestinal motility, secretion and emptying (2, 3). Naftali et al., have concluded that these properties may explain why cannabinoids have a beneficial effect on inflammatory bowel disease (IBD) (4).
In experimental animal models, marijuana and individual cannabinoids have been shown to be beneficial in trials on different models of colitis, particularly in the reduction of inflammation (summarized in ref 4). Apparently not only CB1/CB2 receptors are involved. Recently a GPR55 receptor antagonist was shown to protect against intestinal inflammation (5). Cannabidiol (CBD), which does not bind to the CB1/CB2 receptors, but is an antagonist on the GPR55 receptor, is a potent anti-inflammatory agent and may act on IBD through the GPR55 receptor.
Lal et al. have recorded information from 100 patients with ulcerative colitis and 191 patients with Crohn's disease attending a tertiary-care outpatient clinic (6). They found that cannabis use is common amongst patients for symptom relief, particularly amongst those with a history of abdominal surgery, chronic abdominal pain and/or a low quality of life index. The mean duration of cannabis use (current or previous) was 7 years (range four months to 30 years). Most cannabis users [76/136 (55.9%)] reported doing so once per month or less, although a significant minority [23/136 (16.2%)] reported using cannabis at least daily or several times per day. 77.2% of users smoked cannabis as a joint without tobacco, 17.7% of users smoked it with tobacco, 2.9% used a water pipe, whereas 1% reported oral ingestion.
Ravikoff Allegretti et al. have surveyed 292 patients with IBD. Above 40% were past or present marijuana users (7). Among these users, 16.4% of patients used marijuana for disease symptoms. The authors found that most users felt that marijuana was "very helpful" for relief of abdominal pain, nausea and diarrhea.