Session 10.1 - GI Pharmacology Flashcards
Gaviscon
Drug Class: Alginate and Antacid
Mechanism of Action:
Antacids - buffers stomach acid
Alginates - increase stomach content viscosity & reduce reflux
Common Indicators: Gastro oesophageal reflux, Heartburn
ADRs: Mg salts can cause diarrhoea & Al salts can cause constipation
Contraindications:
Na+ and K+ containing preparations should be used in caution in renal failure
High [sucrose] in some preparations - hyperglycaemia in DM
Important drug-drug rxns:
Reduces absorption of drugs
Increased urine alkalinity causes increased aspirin excretion
Lansoprazole
Omeprazole
Drug Class: Proton Pump Inhibitor (PPI)
Mechanism of Action: irreversibly inhibits the H+/K+ ATPase in parietal cells, reducing stomach acid secretion
Common Indicators: Prescribed with NSAIDs/steroids to reduce ulceration risk, gastric ulcers, duodenal ulcers, gastro oesophageal reflux
ADRs: GI disturbance - abdo pain, constipation, diarrhoea
Headaches, dizziness
Contraindications: Masks symptoms of gastro-oesophageal cancer
Osteoporosis - increases fracture risk
Important drug-drug rxns: Omeprazole = CYP inhibitor - reduced clopidogrel action, PPIs can increase effects of warfarin
Rantidine
Drug Class: Histamine receptor antagonist
Mechanism of Action: inhibit H2 receptors (histamine from ECL cells activates proton pumps)
Common Indicators: gastric ulcers, duodenal ulcers, gastro oesophageal reflux
ADRs: generally well tolerated, may contain carcinogenic contaminant
Contraindications: Masks symptoms of gastro-oesophageal cancer, renal impairment
Important drug-drug rxns: few DDIs
Mesalazine
Drug Class: Aminosalicylate
Mechanism of Action: Topical anti inflammatory action at the colon
Common Indicators: Ulcerative colitis
ADRs: GI disturbance - nausea, dyspepsia
Leukopenia
Contraindications: Similar aspirin hypersensitivity
Important drug-drug rxns: Enteric coated tablets may break down quicker in presence of PPIs (increased pH)
