Pharm Flashcards
What are peptic ulcers?
- Peptic ulcer involves breakdown of the protective mucosal layer in one particular region of
- the stomach or upper duodenum resulting in an ulcer which may be painful as a result of irritation by acid and pepsin.
- H. pylori and NSAID use are important risk factors for peptic ulcers
Describe a pathway by which HCL is secreted into the lumen of the stomach (1)
- Vagus
- →releases Ach
- →Musc receptors on ECL cells
- → stimulate M1 receptors
- → release of histamine
- →histamine binds to H2 receptor on parietal cell
- → Parietal cell releases gastric acid (HCl)
Describe a pathway by which HCL is secreted into the lumen of the stomach (2)
- Vagus
- →releases Ach
- →G cell releases gastrin
- →gastrin acts on ECL cell OR
- →Parietal cell
- → Parietal cell releases gastric acid (HCl)
Describe a pathway by which HCL is secreted into the lumen of the stomach (3)
- Vagus
- →releases Ach
- →stimulates parietal cell directly
- →parietal cell releases gastric acid (HCl)
What is a PPI?
How does it work?
H+/K+ ATPase inhibitors/Proton Pump Inhibitors
It irreversibly destroys the proton pump
Therefore it decreases gastric acid secretion
What are the PPIs you need to know?
- Omeprazole (1st PPI ever)
- Esmomeprazole (most important one – v v v popular)
- ‘OLE’
What is a Histamine H2 antagonist?
How does it work?
Inhibits histamine from binding to H2 receptor on parietal cell
thus parietal cell cannot releas gastric acid (HCl)
What Histamine H2 antagonist do you need to know?
Ranitidine (Zantac – main one used)
What is better H2 antagonist or PPI?
PPIs
What is the treatment for H. pylori?
Must eradicate H pylori to make ulcer doesn’t return. Therefore use PPI & amoxicillin & clarithromycin
How do antacids work?
• neutralize gastric acid
What are the side effects of the components of antacids?
- Mg → diarrhea
- Al → constipation
- Ca →constipation/ hypercalcaemia
Why are antacids used, what are the drawbacks of its use?
- Symptomatic relief
- Some are short acting, some are long acting.
- Combine all these salts (Mg, Al, Ca) to ↓ SEs.
- When you stop taking them, they stimulate rebound hyperacidity.
How do muscurinic receptor antagonists work?
i. Muscarinic receptor antagonist block ACh (normally increases motility)
What is an muscurinic antagonist spasmolytic?
• hyoscine butylbromide (Buscopan)
What are the direct spasmolytics and how do they act?
Direct spasmolytic (act directly on SM to relax it) = mebeverine, peppermint oil
How do PGE analogues work?
- ↑ mucous secretion
- ↑ mucosal blood flow (removes XS H+)
- ↓ gastric acid secretion
When are PGE contraindicated?
- Severe diarrhoea
* ↑ uterine contractions (don’t use in pregnant women)
What is the name of a PGE analogue?
• Misoprostol
What is the Chemoreceptor trigger zone (CTZ)
The CTZ is located in the medulla outside the blood brain barrier. It communicates with other structures in the vomiting centre to initiate vomiting.
As a result of its position outside of the BBB it is sensative to toxins, bacteria, drugs
Name a H1 receptor antagonist?
Promethazine
Where does promethazine act?
In the gut - it does not enter the CNS
What is a side effect of H1 receptor antagonists?
Sedative
Name a muscurinic receptor antagonist?
Hyoscine hydrobromide
What are some features of hyoscine hydrobromide
It is absorbed and enters into the CNS
What are some side effects of muscurinic receptor antagonists?
Sedative
Anti-SLUD
What are the 2 classes of drugs which act against motion sickness?
Histamine H1 receptor antagonists
Muscarinic receptor antagonis
What are the drugs that act on CTZ stimulated emesis?
Dopamine D2 receptor antagonists
5HT3 receptor antagonist
What are some side effects of D2 receptor antagonists?
- Sedation
- prolonged blockade of D2s (difficulty moving (parkinson’s like symptoms)
- Extrapyramidal SEs (tardive dyskinethesia)
- Late onset, irreversible
What are some D2 RAs?
- Metoclopramide (maxillon)
- Prochlorperazine (Stematil)
- Domperidone (doesn’t cross BBB)
What is a 5HT3 receptor antagonist?
ondansteron
When is ondansteron used?
- Used to prevent extreme nausea caused by anaesthetics and chemotherapy
- V effective
Side effects of ondansteron?
Minor GI upset
Can cause constipation and headaches
What are some features of Metoclopramide?
Also has 5HT3 antag properties in higher doses.
• Can also act as agonist on 5HT4 receptors (acts in the gut here)
• Also facilitates gastric emptying by releasing [Ach] from 5HT4 receptors s absorption of drugs (v important for ppl with migraines who have a lot of nausea.
• Doesn’t cause gastric emptying in colon (ie TF doesn’t cause diarrhoea.
• Used in gastroparesis (delayed gastric emptying) occurs in nerve damage or diabetes.
What do saline laxatives do?
Saline Laxatives – these are slowly absorbed ions which cause osmotic fluid retention → colonic stimulation by distension due to increased fluid volume
Name a saline laxative
Magnesium sulphate (Epsom salts®), Sodium phosphate, Sodium citrate
What are bulking agents?
Hydrophobic colloids; indigestible fibre -> greater faecal water retention -> greater volume of intestinal contents -> increased normal reflex bowel activity
Name some bulking agents?
Bran, psyllium, isphaghula husk, sterculia
What are Faecal softeners and lubricants?
Detergents; enhance mixture of water in faeces
Name 2 Faecal softeners and lubricants ?
Docusate, poloxamer
Name a lubricant mineral oil?
Liquid paraffin
How do disaccharide (galacto-fructose) hydrophilic colloid laxative?
Differs from bulk laxatives in that it increases the bulk of colonic contents by osmosis
Name a Disaccharide (galacto-fructose) Hydrophilic Colloi
Lactulose
How do polyols work?
often added to confectionery as an artificial sweetener – similar action to lactulose
Name a polyol
Sorbitol
How do Macrogols or Polyethylene Glycols (PEGs) work?
Inert polymers of large molecular weight – electrolytes are usually added to maintain balance
What are PEGs?
Bowel preparations
What are other osmotic laxatives?
Other – may also have lubricating and mild stimulant properties – usually in suppository form 1. Glycerol
What are stimulant laxatives?
unknown mode of action; may stimulate colonic myenteric plexuses, irritate intestinal mucosa or by direct sensory nerve ending increase motility; may also reduce net reabsorption of water and electrolytes
What are some stimulant laxatives?
Bisacodyl, sodium picosulphate, senna, frangula
What are Antidiarrhoeal drugs?
Opioids
Musculotropic antispasmodic
Muscarinic Receptor Antagonists
How do opiods work as antidiarrhoeal drugs?
Most commonly used (cause constipation); stop ACh release and slow down movement of the bowel
Name an opid antidiarrhoeal drug?
Loperamide (immodium)
Name a Musculotropic antispasmodic drug?
Mebeverine
Name a Muscarinic Receptor Antagonistsantispasmodic drug?
Hyoscine butylbromide
How do anti-flatulence agents work?
Agents used for treatment of flatulence = defoaming agent which results in coalescence of gas bubbles (1 big air bubble now passes more effectively).
What is an Anti-flatulence agent?
Simethicone
