Pharmacology Flashcards
What is a laxative?
Agents used to treat constipation
What are purgatives?
Drugs which deliberately cleanse or purge the GI tract by prompting evacuation i.e. used before surgery or before a colonoscopy
When should laxatives and purgatives not be used?
If there is a known bowel obstruction
In what way can laxatives be wrongly used?
If people use them to regulate bowel movements - cause laxative dependency
When used in eating disorders
Can disguise underlying disease
What is laxative dependancy?
occurs because the laxative completely clear out the colon so they increase the time in which the person needs to defecate again
What can laxatives do?
Increase peristalsis and soften faeces causing or assisting evacuation
when should laxatives be used?
when straining is damaging
to clear the bowel before surgery or endoscopy
to treat drug induced constipation
How do bulk laxatives work?
Retain water but increase bulk and peristalsis
How do osmotic laxatives work?
retain water but increase bulk and peristalsis
how do stimulant purgatives work?
increase water and electrolyte secretion, increase peristalsis and faecal softening
How do faecal softeners work?
increase water and electrolyte secretion, increase peristalsis and faecal softening
Give an example of bulk laxatives
methylcellulose which is given orally
give an example of osmotic laxatives
magnesium sulphates or hydroxide given orally
give an example of stimulant purgatives
bisacodyl given orally
give an example of faecal softners
docusate given orally
Treatment to reduce acid secretion in peptic ulcer disease?
PPIs e,g, omeprazole, iansoprazole, pantoprazole
Histamine H2 receptor antagonists
What is the mechanism of NSAIDs?
COX 1 inhibitor which reduces prostaglandin formation
What is the mechanism of PPIs?
Inhibits the active H+/K+ dependant ATPase
Which antiemetics are used in chemotherapy?
5-HT3 receptor antagonists
Dopamine receptor antagonists
NK1 receptor antagonists
Cannabinoid CB1 receptor antagonists
Which antiemetics are used in gastro-disorders?
Dopamine receptor antagonists
Which antiemetics are used for sever nausea and vomiting?
Phenothiazides
Which antiemetics are used for motion sickness?
Muscarinic acetylcholine receptor antagonists
Histamine H1 receptor antagonists
Which antiemetics are used against irritants of the stomach?
Histamine H1 receptor antagonists
Give an example of a 5-HT3 receptor antagonist
Ondansteron, palonosteron
What are the side effects of 5-HT3 receptor antagonists?
Constipation and headaches
Give examples of dopamine receptor antagonists
Domperidone, metoclopramide
How does dopamine receptor antagonists work?
Centrally blocks D2 and D3 receptors in the CTZ snd helps control acid reflux in the oesophagus
What are the side effects of dopamine receptor antagonists?
Disorder of movements
Give an example of an NK1 receptor antagonist
Aprepitant
How do NK1 receptor antagonists work?
antagonism of substance P which causes vomiting and is released by vagal afferents
What are NK1 receptors used with?
5-HT3 receptor antagonists
Give an example of a cannabinoid CB1 receptor antagonist
Nabilone
How to cannabinoid CB1 receptor antagonists work?
stimulate the CTZ - involves opiate receptors
What are the side effects of cannabinoid CB1 receptor antagonists?
Drowsiness, dizziness, dry mouth and mood changes
How do phenothiazines work?
Blockage of dopamine D2
Give examples of muscarinic acetylcholine receptor antagonists
Hyosine, scopolamine
What are the side effects of muscarinic acetyl choline receptor antagonists
Blurred vision, urinary retention, dry mouth and sedation
Give examples of histamine H1 receptor antagonists
Cyclizine, cinnarizine - i.e. anything ending in “zine”
How do histamine H1 receptor antagonists work?
Blockage of H1 receptors in the vestibular nuclei and NTS
Give an example of an H2 receptor antagonist?
Ranitidine
When are H2 receptor antagonists used?
Peptic ulcers, reflux, oesophagitis
When are PPIs used?
Peptic ulcers, GORD, acid hyper-secretion
Give examples of mucosal strengtheners
Sucralfate and bismuth chealate
How does sucralfate work?
binds to ulcer base and forms a complex gel with mucus to provide a mucosal barrier against acid and pepsin
What is bismuth chealate toxic to?
H. Pylori
