Drug Use in Alimentary Disease
The diagram below shows the mechanism of action of these drugs.
NICE Guideline 184 on Dyspepsia gives useful guidance on how these drugs might be used in clinical practice.
Drugs which 'speed up' or 'slow down' passage of food bolus through the gut or affect smooth muscle contraction can be used to treat symptoms of vomiting, abdominal pain, diarrhoea and constipation. They may be particularly used in irritable bowel syndrome.
The diagram below outlines where these drugs work.
Laxatives work by chemically stimulating the sensory nerves (stimulant) or by mechanically stimulating it (bulk, osmotic laxatives cause stretch by retaining water in the gut). Faecal softeners soften gut contents by direct action.
Vomiting is more often targeted by central nervous mechanisms, rather than GI ones (although dopamine antagonists can be helpful by increasing gut motility), as below.
A number of drugs can be used by oral, I.V. and rectal routes to reduce the inflammation found in both Crohn's disease and ulcerative colitis. The diagram below shows the mechanisms of action of these drugs (in a simplified model of inflammation).
Aminosalicylates mechanism of action is not clearly known.
Note that the anti-inflammatory drugs above may be used in a range of other inflammatory diseases.
Students are not expected to know which drugs would be used in particular clinical situations as this is a specialist subject.
