F5. Pharmacological treatment of the lower GI tract Flashcards
Changing Motility of The GI Tract Required For…
-Bloating,Nausea&Vomiting-Increase gastric emptying.
-Constipation-Increase lower GI motility.
-Diarrhoea-Decrease lower GI motility.
-Irritable bowel syndrome-Reduce spasm to reduce pain.
what is nausea?
Unpleasant sensation of wanting to vomit. Stimulation of dopamine receptors inhibits gastric motility causing postprandial bloating and contribute to nausea.
What is vomiting (or emesis)?
The forceful expulsion of the gastric content out through the mouth.
Nausea and vomiting is stimulated by?
-Toxins: bacterial poisons, alcohol (15%).
-Smells.
-Motion sickness.
-Migraine.
-Pregnancy.
-Drugs
Describe the coordinated physiological response of nausea and vomiting
-Discomfort, dry mouth, salivary inhibition.
-Yawning – sympathetic distress.
-Reappearance of saliva.
-Pylorus closes.
-Tone of stomach increase.
-Deep breath.
-Contraction of abdominal muscles to force food out.
-Forced expiration to prevent inhalation.
what neurotransmitters are involved in nausea and vomiting?
-Histamine.
-Acetylcholine.
-Dopamine.
-5-Hydroxytryptamine (5-HT).
-Neurokinin (NK1) (Substance P).
Blocking these receptors in the brain prevents Nausea & Vomiting
Central control of nausea and vomiting?
ONE NOTE
What do laxatives and purgatives do?
Increase transit of food through GIT
osmotic laxatives?
lactulose, macrogols, Magnesium sulphate & magnesium hydroxide
ONE NOTE
Describe lactulose (disaccharide of galactose and fructose)
-Metabolised by colonic bacteria into lactic and acetic acid.
-Rise fluid volume osmotically.
-Delayed effect approx. 48 hours.
Describe Macrogols (Movicol, Idrolax)
-Sequester fluid in bowel.
-E.g. Bowel cleansing preps - Klean prep.
Describe Magnesium sulphate & magnesium hydroxide
Remain in lumen & retain water.
Describe faecal softeners
-Docusate sodium/Liquid paraffin/Arachis oil
-Detergents which soften stools and ease defecation.
-Docusate also is a weak stimulant.
ONE NOTE
Stimulant purgatives?
senna extracts, dantron, bisacodyl (Dulcolax)
Describe Senna extracts
-Enter the colon & metabolised to anthracene derivatives.
-Stimulate GIT activity by irritation.
Describe Dantron
A GIT irritant, limited for terminal care only due to potential carcinogenicity.
E.g. Co-Danthrusate (Dantron with docusate).
Describe bisacodyl (Dulcolax)
Usually taken as suppository.
Rapid effect (1-2 hours).
Stimulate rectal mucosa causes peristaltic
action and stimulates electrolyte secretion.
Describe diarrhoea
-Symptom of numerous conditions that increase bowel motility.
-Cause secretion or retention of fluids in the intestinal lumen as well as irritation/inflammation of GI tract.
Causes of diarrhoea?
-Often bacterial or viral infection!
-Rotaviruses: Damage the small bowel villi.
-Invasive bacteria: Damage the epithelium.
-Cytotoxins: Damage the mucosa. E.g. Campylobacter.
-Adhesive enterotoxigenic bacteria: adhere to brush
border, leading to Cl- and Na+ secretion followed by
water.
-Amoebae & giardia also cause diarrhoea.
Goals of treatment for diarrhoea?
-Control the loss of fluids: Oral Rehydration Therapy (ORT).
-Identify and treat causes.
-Provide symptomatic relief: antidiarrheal drugs.
Describe Oral Rehydration Therapy (ORT)
-special combination of salts and sugar
-Young & old are particularly at risk of dehydration.
-Also, patients on concurrent diuretic treatment.
-ORT in association with Zinc to avoid risk of GI infections and impaired immune functions.
what opiates and give examples
-opiates are antidiarrheal drugs
-Loperamide, Codeine, Antimuscarinics
Describe Loperamide
-Reduce motility of lower GIT allowing reabsorption of water and reducing watery stools.
-Allows bowel control and normal daily activities.
-Symptomatic relief.
Describe Codeine
-Aderivativeofmorphine.
-Usedasananalgesic.
-Used as ananti-tussive (cough medicines)
-All opioids (including morphine) can cause constipation.
Describe antimuscarinics
-Not primary therapy for diarrhoea due to effects at muscarinic receptors around the body
-Inhibits secretions and may cause dry mouth, dry eyes & dry skin.
-Causes tachycardia, mild restlessness at low doses,& agitation at higher doses.
-Buscopan used for irritable bowel syndrome.
Describe Inflammatory Bowel Diseases
ONE NOTE
