Pharmacology Flashcards
What is an example of a PPI?
omeprazole and lansoprazole
How do PPIs work?
- Irreversibly block proton pump in apical membrane of parietal cells
- Reduce acid secretion (final common pathway of secretagogues)
- activated in an acidic environment (prodrugs)
- absorbed in the small intestine then transported back to the stomach
What are PPIs used for?
- peptic ulcers
- relief of dyspepsia and GORD
- used to remove H. pylori (with clarithromycin and amox or metron)
What is an example of a histamine type 2 receptor antagonist?
ranitidine
How do histamine type 2 receptor antagonists work?
- Competitive antagonists of histamine channels on basolateral membrane
- Increase in cAMP which activates protein kinase A
(-Less effective than PPIs)
What are histamine type 2 receptor antagonists used for?
peptic ulcer disease or symptomatic relief of dyspepsia or GORD
What is an example of an alginate/antacid?
gaviscon
How do alginates/antacids work?
- short-term relief from dyspepsia
- proton buffers to increase pH of gastric juice
- Inactivates pepsin irreversibly
- Alginates produce foam for barrier so no reflux
What are alginates/antacids used to treat?
symptoms of GORD and short-term dyspepsia
What is an example of an antimuscarinic drug?
hyoscine butylbromide
How do antimuscarinic drugs work?
- Competitive antagonist of muscarinic ACh receptors
- Blocks parasympathetic effect of ACh binding to M3
What is an antimuscarinic drug used to treat?
Relieves muscle spasm in IBS
What is the most common antimotility drug?
Ioperamide
How do anti motility drugs work?
- Agonist of opioid
- Increase tone of smooth muscle and constricts sphincters to cause constipation with inhibition of peristalsis
What are anti motility drugs used for?
acute diarrhoea for symptoms, for IBS symptoms or analgesia for acute pain
What are the most common aminosalicylates?
Mesalazine and Balsalazide
How do aminosalicylates work?
- Anti-inflammatory and immunosuppressive effects on the colon
What are aminosalicylates used for?
UC or rheumatoid arthritis
What is the most common bulk forming laxative?
Ispagula husk
How do bulk forming laxatives work?
- Polymers which are not digested in SI so increase bulk of stool
- water moves into SI and colon so increases bulk and peristalsis
- 2-3 days to work
What are bulk forming laxatives used to treat?
constipation and faecal impaction
mild chronic diarrhoea with diverticular disease
IBS
What are main osmotic laxatives used?
lactulose
macrogols
phosphate
How do osmotic laxatives work?
- They are sugars or alcohols that increase bulk and peristalsis
- Lactulose reduces ammonia absorption
When are osmotic laxatives used?
- constipation
- faecal impaction
- bowel preparation before surgery or endoscopy and hepatic encephalopathy (lactulose)
What is the most commonly used stimulant laxatives?
senna
How do stimulant laxatives work?
- Increase electrolytes so water secretion from colon which stimulates peristalsis
- Act on enteric nervous system
What are stimulant laxatives used to treat?
Constipation or faecal impaction
What are the most common antiemetic dopamine D2 receptor antagonists?
domperidone and metoclopramide
How do antiemetic dopamine D2 receptor antagonists work?
- Antagonist of dopamine receptors in CTZ outside of BBB
- Relaxes the stomach and LOS and disrupts gastroduodenal coordination
What are the most common antiemetic histamine H1 receptor antagonists?
cyclising and cinnarizine
How do antiemetic histamine H1 receptor antagonists work?
Competitive antagonism of H2 receptors in the vomiting centre and block of M1 ACh
What are antiemetic H1 receptors antagonist used to treat?
Treats nausea and vomiting esp in motion sickness and post-operative
What is the most commonly used antiemetic phenothiazine?
Prochlorperazine
How does antiemetic phenothiazines work?
Competitive antagonism of dopamine, histamine and muscarinic receptors in the vomiting centre, vestibular system and in the gut
What are antiemetic phenothiazines used to treat?
Nausea and vomiting eg vertigo, chemotherapy or psychiatric disorders
What is the most common antiemetic 5-HT3 receptor antagonist?
ondansetron
How do antiemetic 5-HT3 receptor antagonists work?
Competitive antagonism of inotropic 5-HT3 receptors in CTZ, NTS and on vagal afferents fibres of GI tract
What are antiemetic 5-HT3 receptor antagonists used to treat?
nausea and vomiting with chemo and radiotherapy and after surgery with general
