Pharmacology Flashcards
When should laxative treatment be considered?
When other measures such as change to diet/ increased exercise haven’t made a difference
Only use for a short period of time
What is the MOA of bulking laxatives?
Cannot be digested by small intestine -> increased mass in stool
Increased mass -> increased water absorption
Bulkier stool -> peristalsis -> SHITTTTTT
Name 2 bulking laxatives?
Ispaghula husk
Methylcellulose
What are the 2 contradictions to bulking laxatives?
Bowel obstruction
Ileus
What is the MOA of osmotic laxatives?
Cause osmosis -> increase bulk of stool -> peristalsis -> SHITTTT
Name 2 osmotic laxatives
Lactulose
Macrogols
What is the contradiction for all osmotic laxatives?
Bowel obstruction
What is the MOA of stimulant laxatives?
Increase motility -> increase movement of stool
Increase water excretion -> increase bulk of stool -> peristalsis
Name 2 stimulant laxtaives
Senna
Glycerol suppository
What is the contradiction?
What is the result of prolonged use?
(of stimulant laxatives)
Bowel obstruction
Atonic colon
What is the side effect of stimulant laxatives in general and the specific side effect of Senna?
Abdo pain
Hypokalaemia
What cell produces HCl?
Parietal cell
How are HCO3- and H+ produced?
Breakdown of carbonic acid
What ion is HCO3- pumped out of the cell in exchange for?
Cl-
What is H+/K+ ATPase also called?
Proton pump
What do secretagogues do?
Agents that cause secretion
HAG - histamine, ACh, gastrin
Match the following secretagogues to their receptor found on parietal cells
- Histamine
- ACh
- Gastrin
(HAG)
Histamine - H2
ACh - M3
Gastrin - G/CCK2
Fill the gaps:
Secretagogues can cause an increase in the number of …. which leads to ….. acid production
Proton pumps
Increased
How do PPIs decrease HCl production?
IRREVERSIBLY inhibit the proton pump
When should PPIs be taken?
20 mins before food
Name 2 PPIs
Omeprazole
Lansoprazole
-prazole
What 3 adverse effects are associated with PPIs
Increased risk of C.diff (less acidic stomach environment)
Masks symptoms of gastric malignancy
Osteoporosis
How do H2 receptor antagonists decrease HCl production?
Block H2 receptors so histamine cannot act on parietal cell
Why are H2 antagonists less effective than PPIs?
They only block H2 receptors so ACh and gastrin can still act on the cell
Name 2 H2 receptor antagonists?
Ranitidine
Cimetidine
-tidine
What adverse effect is associated with H2 receptor antagonists?
Masks gastric malignancy
How do compound alginates work?
Antacid and alginate function
Antacid = increase pH in the stomach
Alignate = foam layer that protects the oesophagus (think Gaviscon)
Name 2 compound alignates
Peptac
Gaviscon
What 2 substances reduce secretagogue action and inhibit gastric acid secretion?
What else is known to inhibit gastric acid secretion?
Somatostatin
Prostagladins
Nausea
What do NSAIDs inhibit?
Why is this an issue?
COX-1 (involved in prostagladin production)
Reduce production of prostagladins -> increase HCl -> increased risk of peptic ulcers
Name 4 NSAIDs that if you see on a drug history you must be thinking of peptic ulcers
Aspirin
Ibuprofen
Diclofenac
Naproxen
What drug can be used for NSAID induced peptic ulcer prophylaxis?
Misoprostol
What anti-emetic MUST be avoided in bowel obstruction?
Why?
Metoclopramide
Encourages gastric emptying
Define nausea
Unpleasant sensation normally felt in the throat and stomach
Define emesis
Forceful expulsion of gastric/intestinal contents out the mouth
Define retching
Rhythmic reverse peristalsis
Involuntary abdo and diaphragm contraction
What stops to allow emesis? (2)
Intestinal slow wave activity
Breathing
What “powers” emesis?
Vomiting centre of medulla oblongata
Are stomach muscles contracted or relaxed in emesis?
What muscles are involved?
Relaxed
Diaphragm and abdo muscles contract
(common mistake)
What is the most common consequence of vomitting?
Dehydration
Which biochemical abnormality can occur in mass vomiting?
Metabolic alkalosis
What is a mallory Weiss tear?
Oesophageal damage
What type of antiemetic is commonly used for anti-nausea in chemo-therpay paitents?
5-HT3 anatagonists “setrons”
Ondanesteron
Palonosteron
(Imagine Dan Ross in chemo)
What is the common antiemetic used for travel sickness?
Hyosine (high in plane - travel - hyosine)
Muscarinic acetylcholine
Which antiemetic is used in conjunction with morphine?
Metoclopramide
Diarrhoea = … loose stools in …hrs
3 in 24 hrs
What are the 4 causes of diarrhoea?
- Activation of CFTR (e.g. by bacterial entertoxins)
- Impaired absorption of NaCl
- Non-absorable or poorly absorbable solutes in the lumen
- Hypermotility
What recpetor do synthetic opiods act on?
Where is this receptor expressed?
Opiod receptors
Enteric neurons
What is the action of the synthetic opiods?
Inhibit ENS -> decreased peristalsis -> increased fluid absorption -> constipating
Name 2 synthetic opiods?
LOPERAMIDE
Codeine phosphate
What are the 4 contradicitions of synthetic opiods?
Remember ABCD Acute UC Babies C.diff infection Dysentary
What transporter is involved in the absorption of Na+ and glucose from the rehydration salts?
SGLT1
What “follows” the rehydration salts?
Water (absorbed too)
Metoclopramide MoA?
Dopamine antagonist
Describe and explain cyclizine?
Anti-histamine drug
Bind to H1 in brain
Indicated in motion sickness
