Inflammatory bowel diseases
Inflammatory bowel disease (IBD) is a group of disorders caused by chronic inflammation of the intestines. The two most common forms of IBD are Crohn's Disease, which can affect any part of the upper or lower GI tract, and ulcerative colitis that affects only the large intestine or colon and rectum. Both diseases are thought to be autoimmune diseases due to an over-reactive immune system, when the immune system attacks self, in this case, intestinal tissue. Symptoms vary from mild to severe when inflammation flares up with symptoms including, abdominal pain and cramping, rectal bleeding, diarrhoea and vomiting. Medications used for treating IBD to relieve symptoms include:
- Anti-inflammatory drugs like Mesalazine that inhibit the cyclo-oxygenase enzyme (COX) and block the production of inflammatory chemicals like prostaglandins and leukotrienes, which also inhibits the migration of inflammatory cells like macrophages into intestine wall.
- Immunomodifiers like sulphasalazine, which have anti-inflammatory, immunomodulatory and immunosuppressive effects and work by several different mechanisms, including, inhibiting production of inflammatory chemicals like prostaglandins and leukotrienes, which are also involved in immune reactions, influencing white cell function and inhibiting antibody production.
- Corticosteroids like budesonide, which are also anti-inflammatory but work by a different mechanism, binding to a glucocorticosteroid receptor in the intestinal cells and inhibiting the production of inflammatory cytokines and cytokine-mediated immune responses.
Irritable bowel syndrome
Irritable bowel syndrome (IBS) covers a range of functional bowel disorders and includes conditions like chronic irritable colon (spastic colon), spastic constipation, spastic colitis and nervous diarrhoea. IBS has no specific cause but may be triggered by several factors, including food sensitivity, stress and infection. Symptoms are caused by spasm of the intestinal muscle as it squeezes food through the intestine and include abdominal pain and cramps, diarrhoea (with or without alternating constipation) and flatulence (wind). Medications used for treating IBD include:
- Antispasmodics like mebeverine and propantheline that are both anticholinergic and work primarily by blocking the action of the neurotransmitter acetylcholine that is involved in regulating intestinal smooth muscle contraction. This action allows the smooth muscle to relax, reducing muscle spasm.
- Serotonin agonists like tegaserod that also regulate intestinal smooth muscle contraction by binding to specific serotonin receptors found only in the nerve cells of the GI tract and this helps restore normal bowel motility; it also helps reduce sensitivity to pain and discomfort caused by symptoms of IBS.
Chronic constipation may be a symptom of several GI disorders and is characterised by hard stools that are difficult to pass and infrequent bowel movements. Laxatives like lactulose help soften the stools by changing the osmotic pressure in the colon and allowing water to be drawn into the colon, which also increases bowel motility and makes the stools easier to pass.