Pharmacology Flashcards
how are HCO3- and H+ produced
from carbonic acid
what ion is HCO3- pumped out of the parietal cell in exchange for
Cl-
H+/K+ ATPase also called
proton pump
3 receptors on parietal cells
M3 - ACh
G/CCK2 - gastrin
H2 - histamine
all cause increases acid secretion when bound
making HCl in parietal cells
carbonic acid is produced by water and CO2 via carbonic anhydrase
HCO3- and H+ are produced
HCO3- is puped out of the cell in exchange for Cl- which are pumped into the canaliculus
H+ and Cl- make HCl
PPI
irreversibly inhibits the proton pump
decrease in HCl production
taken 20 mins before eating
why are PPI taken 20 minutes before eating
same time frame for proton pumps to move to the canalicular membrane before digestion
PPI examples
omeprazole
lanoprazole
pantaprazole
PPI side effects
less acidic stomach reduced defence against infection
masks symptoms of gastric malignancy
risk osteoporosis
H2 receptor antagonists
blocks H2 receptors so histamine cannot act on the parietal cell
decrease proton pumps
decrease HCl production
less effective than PPI
H2 receptor antagonist examples
Ranitidine
cimetidine
famotidine
nizatidine
H2 receptor antagonist side effects
masks symptoms of gastric malignancy
compound alginates
have antacid and alginate function
buffer HCl and make pH in the stomach more neutral (antacid)
increase the viscosity of gastric juice, react with acid to produce a foam layer that protects the oesophagus (alginates)
compound alginates examples
peptac
gaviscon
mucogel
prostaglandins and somatostatin
reduce the effect of the secretagogues and inhibit gastric acid secretion
NSAIDs
inhibit COX 1 which affects prostaglandin production
less prostaglandin is available so increase HCl
increased risk of peptic ulcer
NSAIDs examples
aspirin
ibuprofen
diclofenac
naproxen
misoprostol
prostaglandin E1 analogue
prophylaxis for NSAIS induced peptic ulcer
diarrhoea
loss of fluid and solutes from the GI tract making stool loose and watery > 3 loose stools in 24hrs
leads to dehydration
causes of diarrhoea
activation of CFTR - - more Cl is secreted and Na and water follow
impaired absorption of NaCl - water can’t follow NaCl into the blood so there more water in the lume
non-absorbable or poorly absorbable solutes in the lumen
hypermotility - lumenal contents progree too rapidly down GI tract meaning reduced absorption
synthetic opioids
agonist of the opioid receptors expressed by the enteric neurons
inhibit the enteric nervous system
decreased peristalsis and increased segmentation
increased fluid absorption
overall having constipating effect
synthetic opioids examples
loperamide - imodium
codeine phosphate
diphenoxylate
synthetic opioids contraindications
ABCD acute UC - risk of megacolon and perforation babies - don't give to children C.diff colitis dysentery - bloody diarrhoea
rehydration therapy
fluid and electrolyte replacement is essential in diarrhoea treatment as patients lose lots of electrolytes and water
Na and glucose in the rehydration salts is absored via SGLT1 water follows them and is absorbed too
constipation
passage of <2 bowel movements a week often passed with difficulty straining or pain and a sense of incomplete evacuation
there is a delay in defaecation and enhanced absorption of water
presence of hard, dried faeces within the colon
causes of constipation
lack of fibre and fluid intake
lack of physical activity
drugs - opioids
obstruction
laxatives bulking
indigestible by the small intestine so add to the faecal mass
cause the stool to absorb water
increase bulk of the stool - peristalsis is stimulated
bulking laxative examples
ispaghula husk
methylcellulose
sterculia
bulking laxatives contraindications
bowel obstruction
ileus
osmotic laxatives
cause osmosis - by osmosis, water travels into the stool
increase bulk of the stool - peristalsis is stimulated
osmotic laxatives examples
lactulose
macrogols
phosphate enema
citrate enema
osmotic laxatives contraindications
bowel obstruction
heart failure, ascites, electrolyte disturbances - phosphate enema
stimulant laxatives
stimulate intestinal motility and intestinal secretion
increase mucosal electrolyte and water secretion into intestinal lumen, stimulate enteric nerves
increse bulk of the stool - peristalsis is stimulated
increased intestinal motility - increase stool movement through the intestine
stimulant laxatives examples
senna glycerol suppository bisacodyl docusate sodium sodium picosulfate
stimulant laxatives contraindications
bowel obstruction
prolonged use - atonic colon
stimulant laxatives side effects
abdominal pain
