drugs acting on the gastrointestinal tract Flashcards
name 3 upper gastrointestinal tract disorders
- indigestion (dyspepsia)
- Gastro Oesophageal Reflux Disorder (GORD or GERD America)
- Ulcers
what are the main symptoms of indigestion?
- discomfort or pain in stomach
- bloating, burping, nausea
- heartburn
what are the main causes of indigestion?
- overeating
- pregnancy
- ulcers
- anxiety/stress
what are the main symptoms of gastro oesophageal reflux disorder?
- heartburn - pain in middle of chest
- sour mouth - contents of stomach coming back up
what are the main causes of gastro oesphageal reflux?
- overeating
- pregnancy
- certain drugs
- ulcers
- anxiety/stress
what is an ulcer?
area where damage has occured to mucosal membrane of oesophagus, stomach or duodenum
what are the symptoms of an ulcer?
- pain
- bleeding
what are the causes of ulcers?
- bacterial infection - h.pylori
- NSAIDS
- smoking
- Zollinger-Ellison syndrome
- anxiety/stress
name three types of drugs that are used to treat indigestion, GORD and ulcers
- antacids
- antisecretory drugs and mucosal protectants
- antibiotics (ulcers only)
name four different types of antisecretory and mucosal protectant drugs that are used to treat indigestion, GORD and ulcers
- Histamine H2 antagonists
- Proton pump inhibitors
- Chelates and complexes
- Prostaglandins and analogues
what is the mechanism of action for antacids?
- act locally to neuralise stomach acid → pH now less acidic, pepsin activity reduced
in what form are anatcid preparations available and what might they contain?
liquid or tablet - containing calcium, aluminium or magnesium salts
name 6 antacid prepartions - including 2 with simeticone and 2 with alginates
maalox®
rennies®
with simethicone - asilone®, altacite plus®
with alginates - gavison®, gastrocote®
what is the mechanism of action of simeticone found in some antacids?
alters surface tension of small bubble to allow formation of large bubble whihc are easier to release
explain the mechanism of action of alginates found in some antacids
react with gastric juices to form a raft that floats on top and protect oesophagus from stomach acid
what directions would you give to patients taking antacids?
- take 1hr before or after food
- aluminium may cause constipation
- magnesium may cause diarrhoea
- sleep on left hand side
- may change stool colour
what would need to be considered by the person prescribing antacids?
- electrolyte imbalance - monitor for calcium, phosphate, magnesium and aluminium levels
- low sodium and sugar free versions - important in patients with hypertension, diabetes or liver/kidney impaired
what is the mechanism of action for H2 anatagonists?
- blocks H2 receptors on perietal cells in stomach → reduces acid production in stomach
name four H2 anatagonists
- cimetidine (tagamet®)
- famotidine (pepcid®)
- nitatidine (axid®)
- ranitidine (zantac®)
explain the mechanism of action of proton pump inhibitors
- in acidic pH drug forms two reactive molecules which bind permenantly to proton pump → proton pump never pumps acid again
name 5 proton pump inhibitors (PPIs)
- lansoprazole (zoton®)
- esomeprazole (nexium®)
- omeprazole (losec®)
- pantoprazole (protium®)
- rabeprazole (pariet®)
when and how should PPIs be given?
give 30mins before food - do not crush or chew tablet
PPIs can interfere with the metabolism of certain drugs - name 3
- diazepam
- phenytoin
- warfarin
PPIs interfere withe absorption of some drugs - name 3
- digoxin
- ketoconazole
- ampicillin
can antacids be taken with H2 antagonists?
no
what would you check for in patients taking H2 antagonists?
- blood in stools
- dizziness
- headache
why must particular attention be given when prescribing cimetidine?
can retard the metabolism of other drugs such as - warfarin, phenytoin, theophylline
what is H.pylori?
a gram negative bacteria causingb inflammation of the stomach lining
in which condition is h/pylori routinely treated?
stomach ulcers
what treatment would be used for stomach ulcers?
2 antibiotics plus reduction in acid secretion - ‘triple therapy’ for 7-14 days
which antibiotics would be be used to treat ulcers?
- clarythromycin
- amoxycillin
- metronidazole
- tetracycline
plus PPI or H2 antagonist
what precautions should be takien and what side effects may occur with antibiotics?
amoxycillin - penicillin allergy
clarythromycin and metronidazole - abnormal taste
metronidazole - avoid alcohol
amoxycillin - diarrhoea
clarythromycin, metronidazole, tetracycline - GI upset
what is the mechanism of action of synthetic prostaglandin E1?
- protective - prostaglandins prevent acid production and stimulate mucous release
what are the clinical uses for synthetic prostaglandin E1 ?
NSAID induced ulcers - NSAIDS inhibit COX-1 which produces prostaglandins
who should misoprostol not be given to?
pregnant women - causes premature labour/spontantous abortion
what side effects are associated with misoprostol?
- diarrhoea
- abdominal pain
what is sucralfate? and what is its action?
sucralfate - chelate
action - reacts with acid to form sticky paste - acts locally in stomach to coat ulcers
for how long does sucralfate last?
about 6hrs
what are the side effects of sucralfate?
- constipation
- nausea / vomiting
- metallic taste
why are antispasmodics used in the GI tract and what is their clinical use?
reduce gut motility - relax smooth muscle
uses - irritable bowel syndrome and diverticular disease
what is the site of action of antispasmodics?
intestines
name 4 antispasmodics that act on the muscarinic receptors
- dicyclomine hyrdochloride (kolanticon®)
- hyoscine butylbromide (buscopan®)
- probantheline
- bromide (pro-banthine®)
what side effects are associated with antispasmodics that act on the muscarinic receptors
- constipation
- dry mouth
- confusion (in elderly)
name three othe antispasmodics used to treat irritable bowel syndrome and diverticular disease
alverine citrate (spasmonal®)
mebeverine hydrochloride (colofac®)
peppermint oil (mintec, colpermin®)
what is the site of action for gut motility stimulants?
- intestines
- stomach sphincters
describe the mechansim of action of gut motility stimulants
- dopamine (D2) receptor antagonist →
- increased peristalsis
- relaxes phloric sphincter (increases gastric emptying)
- increases action of oesophageal sphincter
what are the clinical uses of gut motility stimulants?
- nausea and vomiting
- irritable bowel
- dyspepsia
- oesphageal reflux
name two gut motility stimulants
- metoclopramide (maxlon®)
- domperide (motilium®)
what are the side effects of gut motility stimulants?
- movement disorders
- confusion
- restlessness
name two lower GI tract disorders
- constipation
- acute diahorrea
what influences bowel patterns?
- diet
- fluid intake
what are the main causes of acute diarrhoea?
- poor hygiene
- food poisioning (infection)
what is the first line of treatment for acute diarrhoea?
oral rehydration therapy
name two oral rehydration therapies
- dioralyte®
- electrolade®
what does oral rehydration therapy contain? and how does it work?
- contains glucose, water, electrolytes
- stimulates absorption of water and electrolytes
what are anti diarrhoeals used for?
- to treat acute diarrhoea
what is the site of action of anti diarrhoeals?
- large/small intestine
name 3 anti diarrhoeals
- loperamide (immodium®)
- co-phenotrope (diphenoxylate and aptropine)
- kaolin and morphine (kaolin acts locally as an absorbant)
what is the mechanism of action of anti diarrhoeals?
- opiod-related drugs
- reduce peristalsis in small and large intestine
- reduce explosive contraction of colon
what are the side effects of anti diarrhoeals?
- nausea and vomiting
- drowsiness
- constipation
- abdominal discomfort
- fast HR
*caution with alcohol, some painkillers and sedatives
what should be monitored when administering anti diarrhoeals?
- electolyte balance and fluid intake
- GI reactions
- CNS effects
what are laxatives used for?
treatment of constipation
name three different classes of laxative
- bulk forming
- stimulant
- osmotic
what is the mechanism of action of bulk forming laxatives?
- increase faecal mass
- stimulate peristalsis
name three bulk forming laxatives
- ispaghula hulk (fybogel®)
- methylcellulose (celevac®)
- sterculia (normacol®)
what could patients be advised when taking bulk forming laxatives?
- taking a few days to work
- need to maintain/increase fluid intake
what is the action of stimulant laxatives?
- increase peristalsis
- moves stool through large bowel
* for acute use only* can cause lazy bowel
name 4 stimulant laxatives
- bisacodyl
- dantron
- senna (sennokot®)
- sodium picosulfate
what are the side effects and cautions to look out for when administering stimulant laxatives?
- rapid action (6-12hrs)
- can cause abdo pain and cramps
- watch for abuse in anorexia
what are osmotic laxatives and how do they work?
- large sugar/magnesium and sodium salts
- poorly soluble - not easily absorbed so draw water into gut
- makes stool softer and easier to pass
name 5 osmotic laxatives
- lactulose
- macrogols (movicol®)
- magnesium salts
- phophates (carbolox®)
- sodium salts (microlax®)
4 and 5 - rectal use only
what are the side effects of osmotic laxatives?
- abdominal cramps
- wind
- diarrhoea
how long do osmotic laxatives take to work?
- lactulose and macrogols - 2-3days
- magnesium salts - more rapid
can you take osmotic laxatives if you are lactose intolerant?
no - avoid
