GIT Pharmacology Flashcards
Ranitidine MOA
block H2 receptor,
reduce acid secretion
H2-receptor antagonists side effects
general stuff-headache, dizziness, skin rash, nausea, diarrhoea, confusion
impotence and gynaecomastia (rare)
H2-receptor antagonists beware
Elimination mainly via kidneys-so if kidney issue then have to reduce dose
cimetidine interacts with CYP450 enzymes of the liver –ie it can interfere with other drugs
other antisecretory drugs for PUD
Antimuscarinics
Gastrin antagonists
Somatostatin analogues
PPI side effects
very safe, maybe headache, rash, dizziness, rarely gynecomastia and renal impairment
PPI MOA
irreversibly inactivating H+/K+ ATPase proton pump
=reduced secretion of HCl
PPI things to remember
Drug is inactive at a neutral pH, becomes activated in acidic environment
taken 1 hr before meal
dont giv in pt using antacid -wont work cos envrio will be neutral thanks to antacid
Inhibits CYP450 enzymes – drug interactions (but not all –prazoles do this)
PPI core drug
Esomeprazole
sucralfate
for PUD
creates a viscous coating on ulcer
Things that increase the defence side in PUD (aka Cytoprotective agents and mucosal strengtheners)
Sucralfate Prostaglandin analogues Bismuth chelate Carbenoxolone Antacids
bismuth chelate side effect
may cause blackening of stools & tongue
PGE1 analogue (a Prostaglandin analogues) contraindicated in
pregnancy
carbenoxolone job-
this drug is a herbal thingy
promotes the production of mucus
Carbenoxolone AE
alkalosis, hypertension and
hypokalaemia
Antacid job
a weak base that neutralises the acid lol
also inhibit pepsinogen forming to pepsin
antacid side effect
Al3+ antacids-constipation
Mg2+ antacids- diarrhoea
antacid beware
antacid interacts with a lot of other drugs
SO avoid taking antacid 2 hrs before/after taking other drugs
sucralfate -wen to take
1 hr before meals 4 times a day
Do not take antacids or meals within 30min of sucralfate – raised gastric pH alters action of sucralfate
triple therapy
antibiotic treatment for PUD (first line)
PPI + metronidazole + amoxicillin or clarithromycin = triple therapy
drugs promoting reflux-ie bad for GORD
anticholinergics • phosphodiesterase inhibitors • nitrites • calcium channel blockers • dopamine agonists
GORD treatment
PPIs (drug of choice)
antacids, H2 receptor antagonists, sucralfate
osmotic laxatives
o Basically poorly absorbed salts or sugars that draw water into gut so that stuff moves faster.
o Risk of dehydration
o Can cause abdo cramps
o Avoid in kids/ renal damage
bulk laxatives
o BULK LAXATIVES: Basically this sugar compound that is poorly digested and draws in water in lumen forming a bulky hydrated lump in lumen. This increase in mass is a stimulant for peristalsis to occur, water also helps as lubricant
whats the Faecal softeners for constipation
– docusate sodium
osmotic laxatives
o Basically poorly absorbed salts or sugars that draw water into draw water into the contents, softening it and allowing stuff to move faster.
o Risk of dehydration
o Can cause abdo cramps
o Avoid in kids/ renal damage
bulk laxatives
eg metamucil
o BULK LAXATIVES: Basically this sugar compound that is poorly digested and draws in water in lumen forming a bulky hydrated lump in lumen. This increase in mass is a stimulant for peristalsis to occur, water also helps as lubricant
whats the Faecal softeners for constipation
– docusate sodium
surfactant/detergent-like effect
Stimulant laxatives
increase electrolyte and water secretion by mucosa, increases peristalsis
aloe, enna, cascara, bisacodyl, glycerol suppositories
Constipation treatemnt
purgatives.
purgatives include:
laxatives
faecal softeners
stimulatant laxatives
D2 receptor antagonist
Opioids e.g. loperamide job
Antidiarrhoeal Agent^
decreases activity of myenteric plexus
diarrhoea treatment
fluid n electrolyte balance (glucose ‘drinks’ enhance Na+ (and water) absorption)
antiinfective agents eg antibiotic or antiviral
Traveller’s diarrhoea = E.coli
antidiarrhoeal agent -opioid
don’t give muscarinic antagonist
treatment of vomiting
assess cause, replenish water/electrolytes
anti-emetic drugs
anti-emetic drugs
Antimuscarinics
Antihistamines
Dopamine (D2) receptor antagonists
5-HT3 antagonsits
anti-emetic drugs
Antimuscarinics
Antihistamines
Dopamine (D2) receptor antagonists
5-HT3 antagonsits
other: Pyridoxine (vitamin B6) Ginger Carob bean Cannabinoids
antimuscarinics -for vomiting
Hyoscine
prophylaxis and treatment
Blocks ACh receptors
antimuscarinics -for vomiting
Hyoscine
prophylaxis and treatment
MOA: Blocks ACh receptors
se:Blurred vision, urinary retention, decreased salivation, drowsiness
Antihistamines -for vomitin
H1 receptor antagonists
(H2 is for peptic ulcers)
Not useful in chemotherapy induced
se:Blurred vision, urinary retention, dry mouth
Dopamine (D2) receptor antagonists -for vomitin
e.g. domperidone
MOA;block D2 receptors in CTZ
5-HT3 antagonsits-for vomiting
e.g. ondansetron
MOA:Works at CTZ, also has a peripheral action
Prevent vomiting in 70-80% of patients on
chemotherapy
Side Effects: constipation
albendazole
drug of choice for mixed intestinal worm infections
