GI Pharmacology Flashcards
What are the 5 main types of anti-ulcer drugs
- Antacids
- Histamine 2 antagonist
- Proton Pump Inhibitors
- Prostaglandin analogues
- Systemic Antibiotics
What are 2 indications for anti-ulcer drugs?
PUD and GORD
What are the 4 compounds that make up antacids?
- Aluminium hydroxide
- Calcium carbonate
- Magnesium salt
- Sodium bicarbonate
Which of the 4 antacid compounds cause a laxative effect?
- Magnesium salt
- Sodium bicarbonate
Which of the 4 antacid compounds cause constipation
- Aluminium hydroxide
- Calcium Carbonate
How do antacids work?
Neutralise gastric acids
Do not take antacids within ___ of other medications
2 hours
How much water needs to be taken throughout the day when taking antacids?
3L
How to avoid laxative or constipation effects when taking antacids?
Combine agents with opposite effects.
Antacids can produce _____ colour ____.
white, stool
What are 2 examples of H2 receptor antagonists?
- Cimetidine
- famotidine
How do H2 receptor antagonists work?
Block the H2 receptor of gastric parietal cells. This reduces HCL secretion.
H2 receptor antagonists cause ____ depression symptoms. Such as ____, ____, _____.
CNS, dizziness, headache, sleepiness
If a drug has CNS depression effect what needs to be considered?
Falls risk, driving, etc.
H2 receptor antagonists has a drug interaction. What is this?
It blocks hepatic enzymes which increase plasma levels of certain drugs. Such as Metformin, betablockers, phenytoin, CCB, opioid analgesics, and oral anticoagulants.
When on H2 receptor antagonists, HR and BP needs to be monitored if administered via ____
IM or IV
What is a very strong anti-ulcer medication?
PPI
How do PPIs work?
Block gastric ATPase enzyme on parietal cells which inhibit the last step of acid formation.
What are 2 examples of PPIs?
Esomeprazole
Omeprazole
What are the indications for PPI use?
H. Pylori induced PUD, chronic gastritis, GORD or erosive esophagitis (cons. Biphosphonates)
PPI treatment should last a maximum of ____
8 weeks
PPIs have a short/long half life.
short - 2-3hrs
What does PPI increase the risks of?
URTI
PPIs block the hepatic enzymes that metabolise what drugs?
- Warfarin
- Diazepam
- Phenytoin
PPI reduce absorption of _____ and ______. Both drugs require gastic pH to be absorbed.
digoxin and ampicillin
What is an example of a prostaglandin analogue?
Misoprostol
What are the indications for Misoprostol?
- prevent NSAID induced gastric ulcers
- treat PUD
- IOL or abortion
What is the action of prostaglandin analogues?
It binds to prostaglandin receptors on parietal cells which decreases gastric acid secretion, increase mucous production and mucosal blood flow.
When in Misoprostol contraindicated?
pregnancy.
What are the ADRs of prostaglandin analogues?
- GI upset
- premature labour
- menstrual disorders
- bleeding/cramps
What drug has a bactericidal effect on H. Pylori and provides a protective layer on mucosa?
Colloidal Bismuth Subsitrate
What anti-ulcer drug can cause black tongue and faeces?
CBS
What is used to treat H. Pylori?
Triple or quadruple therapy of ABs. This is due to the bacteria being very resistant.
What are some examples of ABs that treat H. Pylori?
- Clarithromycin
- Amoxicillin
- Metronidazole
- Tetracycline
What are tests that diagnose H. Pylori?
- Urea breath test
- GI endoscopy
- Stool sample for antigen
What is the treatment for diarrhoea?
- Rehydration and electrolyte replacement
- ABs for severe infectious diarrhoea
- peristalsis slowing drugs for systematic relief
Loperamide and can/cannot cross the BBB. This means it does/doesn’t have a CNS effect
cannot, doesn’t
What are the 5 types of laxatives?
- bulk-forming
- stimulants
- emollients
- osmotic
- lubricants
What is an example of a bulk-forming laxative?
Psyllium - metamucil
What is the 1st line therapy for acute/chronic constipation?
Bulk-forming laxative
What laxative is used for opioid-induced constipation and has a fast onset <30mins?
methylnaltrexone
How do bulk-forming laxatives work?
The substance swells in water which enlarges the stool and promotes peristalsis.
________ laxatives interfere with Ca absorbtion.
bulk-forming
Bulk forming laxative are contraindicated with pt with ______.
GI obstruction.
How long do bulk forming laxatives take to take effect?
2-3 days
Monitor ________ balance while pt is taking laxatives.
electrolyte.
What is an example of a stimulant laxative?
Bisacodyl
Sennosides
What is the indication for stimulant laxatives?
For those who are unresponsive to bulk or osmotic laxatives.
Mod-severe constipation
Post surgery
What is the MOA of stimulant laxatives?
Stimulates nerve endings in intestinal smooth muscle which increases peristaltic movements.
Stimulant laxatives work within ______
6-12 hours.
Overuse of stimulant laxatives may lead to ____ _______. Long term use can lead to _______.
rebound constipation.
dependence.
What laxatives do you need to avoid laying down after taking?
Bulk-forming and lubricant.
What laxatives should be avoided during pregnancy?
stimulant.
What is Docusate?
Emollient/stool softener
How do emollient laxatives work?
Prevent water reabsorption and promote water and electrolyte secretion.
How long do emollient laxatives take to work?
1-3 days
_____ laxatives are indicated for increased ICP and hernias, as they prevent _________.
emollient, straining.
Magnesium sulphate, Sodium sulphate, lactulose, glycerol and sorbitol are all examples of _____.
Osmotic laxatives.
Pt with HTN should avoid what osmotic laxative?
Na osmotic laxative
Pt with DM should avoid what osmotic laxative?
Lactulose
How do Osmotic Laxatives work?
The substance is not absorbable and makes the bowel contents HYPERTONIC. This draws H20 into the intestinal lumen which increases faecal mass.
What laxative is the 1st line for chronic constipation and 2nd line for acute constipation?
Osmotic laxatives.
How long do osmotic laxatives take to work?
1 - 3 hrs
Liquid paraffin is a ____ laxative.
lubricant.
Polyp-like growths and colon cancer are associated with _____.
lubricant laxatives.
What laxative impairs the absorption of vit A, D, E and K?
lubricant laxatives.
Antagonists of Histamine 1, Dopamine 2, Serotonin 5HT3, Neurokinin-1, Acetylcholine/muscarinic are commonly used as _______.
antiemetics.
Anti-emetic agents bind to relevant receptors on ___, _______, ______ centre and ____.
GI, vestibular-apparatus, vomiting centre and CTZ.
Promethazine is a representative of what class?
H1 Antihistamines.
How does promethazine work?
Blocks H1 receptor in the CNS and possibly anti-Ach on the vestibular apparatus.
H1 antihistamines can cause _____ or _______ due to CNS inhibition.
drowsiness, sedation
Hyoscine is an example of a ______
Antimuscarinic/anticholinergic
Anticholinergic action is in the………
Vestibular apparatus and vomit centre. It blocks acetylcholine.
Dopaminergic D2 antagonists are__________ as well as antiemetics.
antipsychotics.
What are examples of dopaminergic D2 antagonists?
- Metoclopramide (crosses BBB)
- Domperidone (does not cross BBB)
What is the MOA metoclopramide?
Block dopamine receptors in CTZ and gut. This increases the rate of gastric emptying and oesophageal tone.
What drug causes extrapyramidal symptoms?
Metoclopramide.
What are extrapyramidal symptoms?
akathisia, psuedoparkinsonism, tardive dyskinesia, dystonia.
Dopaminergic D2 antagonists can cause_____ _____, so they require ____ monitoring.
orthostatic hypotension, BP
Which anti-emetic has a less sedative effect than H1 antihistamines but does cause dry mouth, constipation and blurred vision?
Antimuscarinic/anticholinergics such as Hyoscine
5-HT3 receptor antagonists block ______ receptors in the CTZ and ____.
serotonin, GIT
What is an example of a 5-HT3 receptor antagonist?
Ondansetron.
Ondansetron has more/less ADR compared to metoclopramide.
Less
Ondansetron can cause _______ and _____ ____ so is not for pt with CVD. It can also cause ____.
bradycardia, heart block. Headaches.
What is an example of Neurokinin-1 antagonist?
Aprepitant.
Aprepitant site of action is in the ___, _____ _____ and maybe the ___.
CTZ, vomiting centre and GIT
What are the ADRs of Aprepitant?
Hiccups, diarrhoea
