Clinical Pharmacology Of Antacids, Alginates, H2 Antagonists And PPIs Flashcards
what is a peptic ulcer
break in the mucosa of the stomach or duodenum (gastric or duodenal ulcer)
occurs when theres an imbalance of damaging and protective actions of mucosa
antacids and alginates
antacids used for quick relief of symptoms caused by stomach acids, often a weak base to neutralise excess acid.
aluminium hydroxide, magnesium carbonate, magnesium trisillicate.
given as liquid or oral tablets
alginates can relief GERD symptoms or suppress reflux
can be used alone or with other drugs.
physical mode of action
H2 receptor antagonists
reduces gastric secretion and heal ulcers
randitidine is competitive antagonists and reduces gastric acid secretion
misoprostol agonists of GI receptors, increases production and secretion of protective mucus
side affects and pharmacokinetics of H2 receptor antagonists
confusion, CYP450 enzyme inhibition, cimitidine
given orally
6% metabolised in liver, kidneys excrete parent drugs and metabolites by filtration
Proton Pump inhibitors (PPIs)
inactivate H+/K+ ATPase to reduce acid secretion by 80-90%
Omperazole is a weak base so is stable at PH7.4 so can pass freely into parietal cell
the cytoplasm in the cell is acidic which ionises omeprazole and activates it to sulfanemide
sufanemide reacts with H+/K+ ATPase to form covelent disulphide bond which inhits proton pump
drug absoption Pka and PH
when Pka of PPI = PH of solution 50% will be ionised and 50% will be unionised
so at PH 4 50% of solution will be omeprazole and 50% will be sulfanemide
side effects and pharmacokinetics of PPIs
given orally in enteric coated form to prevent early activation
or can be given as I.V. injection
side effects: nausea, diarrhoea, headaches, GI disruptions, bone fractures
helicobacter pylori
risk factor of gastric carcinoma
urease produces ammonia which damages gastric mucosa and neutralises acid PH which allows H.pylori to survive in the stomach
treatment: omeprazole, amoxicillin
