Pharmacology in Diarrhoea and Constipation

Frage	Antworten
What are the functions of the colon and small intestine?	Water absorption and stool formation
What happens to the surface area of the intestine in diarrhoea?	Surface area for the absorption of nutrients and water is reduced via rapid proliferation - reduced surface area may be due to surgery to remove part of the gut or disease e.g. Coeliac
What are the causes of diarrhoea?	Infection: bacteria, virus (most common), parasites Medications Chronic bowel disorders
Bacteria in infective diarrhoea	E. coli Salmonella enteritidis/thphi Vibrio cholera Campylobacter jejuni C.difficile Shigella
Viruses in infective diarrhoea	Norwalk virus Rotavirus Adenovirus
Parasites in infective diarrhoea	Crytasporidium parvum Entamoeba histolyticaB
Biggest cause of diarrhoea in under 2s?	Rotavirus (22%)
Medications causing diarrhoea	Cholinergics - increased ACh Cytotoxic agents - loss of gut epithelia Broad spectrum antibiotics - change in gut flora
Consequences of diarrhoea?	Dehydration Metabolic acidosis Potassium depletion Hypovolaemia CV collapse Death
Chronic bowel disorders causing diarrhoea	Endocrine disease - diabetes, thyroid disease Inflammatory bowel disease - UC, Crohn's Diverticular disease Laxative abuse Stress Malabsorption syndromes - Coeliac disease Antibiotic associated colitis
Symptoms at 95% hydration	Thirst Skin turgor Tachycardia Dry mucous membranes Sunken eyes Lack of tears Sunken anterior fontanelle Oliguria
Symptoms at 90% hydration	Anuria Hypotension Feeble and rapid pulse Cool and moist extremities Diminished consciousness Signs of hypovolaemic shock
Treatment options for acute diarrhoea	Oral rehydration therapy Antimotility drugs e.g. loperamide Antispasmodics Antibacterials (usually not required)
How does oral rehydration therapy work?	Clean water with glucose and sodium - aids reabsorption of water
What are some examples of antimotility drugs?	Loperamide, codeine, morphine, cophenotrope
How do antimotility drugs work?	Increase muscle tone but diminish propulsive activity Binding of mu receptor in submucosal plexus of GI tract (relatively selective)
Side effects of antimotility drugs	Nausea, vomiting, cramps, paralytic ileus
Examples of antispasmodic drugs	Muscarinic antagonists - atropine, propanthelone, dicycloverine
Mechanism of antispasmotic drugs	Antimuscarinics inhibit parasympathetic stimulation of the intestinal submucosal and myenteric plexus - prevents peristalsis - inhibit gastric emptying
Which antibacterial can be used in the prophylaxis of traveller's diarrhoea?	Co-amoxiclav
Which antibiotics are used in the treatment of acute diarrhoea?	Ciprofloxacin, norfloxacin
Which antibiotic should be used if infective agent is C. difficile?	Metronidazole or vancomycin
What treatments can be used in chronic diarrhoea?	Adsorbants Bulk forming agents Anti-motility drugs
Example of an adsorbant?	Kaolin (clay) - binds toxins following ileostomy, colostomy or diverticular disease
Example of bulk forming agent?	Methylcellulose - used in colostomy, iliostomy and constipation
When should anti-motility drugs not be used in the treatment of diarrhoea?	In children, ulcerative colitis or antibiotic associated colitis
What is the clinical definition of constipation?	Fewer than 3 bowel movements per week (but a change to the normal routine)
What factors increase the risk of constipation?	Female over 65 Before and after pregnancy Following surgery
Reasons for constipation?	Disease - stroke, dehydration, ignoring the urge, laxative abuse, travel, pregnancy, IBS, milk, medications
Diseases associated with constipation	Neurological: MS, Parkinsons, stroke, spinal cord injury Metabolic/endocrine: diabetes, poor glycaemic control, uraemia, hyperkalaemia, hypothyroidism Systemic disorders: amyloidosis, lupus, scleroderma
Agents used to treat constipation	Bulk formers Stimulants Foecal softeners Osmotics
Examples of bulk formers?	Unprocessed wheat bran or ispaghula husk, methylcellulose, sterculia polysaccharide polymers
How do bulk formers relieve constipation?	Increasing foecal mass: bacterial proliferation and hydrophilic action Stimulates peristalsis
When are bulk formers used?	In colostomy, diverticular disease and IBSS
Side effects of bulk formers	Bloating
Examples of stimulants in constipation?	Bisacodyl, dantron, senna (decreasing order of stimulation)
How do stimulants work in the treatment of constipation?	Stimulate myenteric plexus in intestines, stimulate smooth muscle contraction and water and electrolyte transfer
Side effects of stimulants?	Cramp, diarrhoea in long term use, tolerance
How long do stimulants take to work?	6-12 hours (15-30 min with rectal administration)
How long do bulk formers take to work?	24 hours
Examples of foecal softeners?	Docusate, liquid paraffin, arachis oil
Mechanism of foecal softeners?	Increase fat and fluid in stool, lubricate bowels, promote bowel movements
Side effects of liquid paraffin?	Anal seepage and anal irritation, granulomatous reaction, lipoid pneuumonia, reduced lipid soluble vitamin uptake
Examples of osmotics used in constipation?	Lactulose, macrogols, magnesium salts, hydroxide salts
Mechanism of osmotics in constipation?	Withdraw fluid from the bowel or retain the fluid they are administered with
Side effects of osmotics?	Magnesium salts can cause central effects in overdose Can cause dehydration
When are bowel cleansers used?	Before colonic surgery, colonoscopy, radiology - not treatments for constipation
Examples of bowel cleansers?	Sodium acid phosphate, sodium picosulfate
Which drugs are used for symptom relief in acute diarrhoea?	Antimotility and antispasmodic drugs

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Pharmacology in Diarrhoea and Constipation

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