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26 Cards in this Set
- Front
- Back
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MOA of H2 antagonists |
Competitive inhibitors of all histamine type 2 receptors. Inhibit histamine and gastrin stimulated gastric acid secretion by their action on parietal cells in the stomach |
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Indications for H2 antagonists |
Gastric and duodenal ulcers Gastro - oesophageal reflux Treatment and prophylaxis of NSAID associated ulcers |
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Contraindications of H2 antagonists |
Hypersensitiviy If red flag features of malignancy, need to investigate prior to initiating treatment |
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Side effects of H2 antagonists |
GI disturbances, especially diarrhoea Gynaecomastia (cimetidine) |
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Metabolism and half life of H2 antagonists |
Excreted largely unchanged in urine T1/2 2-3hrs |
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Monitoring needed for H2 antagonists |
None |
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Drug interactions of H2 antagonists |
Cimetidine inhibits cytochrome P450 activity in liver and therefore potentiates the action of drugs such as warfarin, phenytoin and theophylline |
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Special uses of H2 antagonists |
Rantidine can be used prior to anaesthesia in patients at high risk of aspiration particularly in obstetric practice (Mendelson's Syndrome) |
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MOA of laxatives |
Bulk laxatives (ispaghula husk) - polysaccharide polymers that are not broken down by digestion and therefore increase stool volume. This stimulates intestinal peristalsis (due to the stretch reflex) a well as softening faeces Osmotic laxatives (lactulose, Movicol) - these poorly absorbed salts increase the volume of water in the bowel lumen by osmosis thus increasing transit Stimulant laxatives (senna, docusate sodium) - the primary effect is via direct stimulation of the myenteric plexus resulting in smooth muscle contrition and increased peristalsis Faecal softeners (arachis oil) - these are surfactants that reduce surface tension and allow water to penetrate and soften faeces |
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Indications for laxatives |
Constipation Hepatic encephalopathy (lactulose - reduces ammonia producing organisms) |
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Side effects of laxatives |
Flatulence Diarrhoea Abdominal cramps Electrolyte disturbances |
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Drug interactions of laxatives |
Lactulose may enhance warfarin effects in severe liver disease |
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Contraindications of laxatives |
Bowel obstruction (risk of perforation) Galactacaemia (lactulose only) Acute inflammatory bowl disease Severe dehydration |
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Monitoring needed for laxatives |
None |
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Metabolism and half life of laxatives |
Variable - most are broken down in the GIT tract with minimal absorption |
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Can laxatives cause tolerence |
Yes, stimulant laxatives cause tolerance in chronic use |
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Metabolism and half life of PPIs |
Extensively metabolised by the liver and excreted by both renal and biliary routes T1/2 varies from 40 min to 2 hrs |
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Side effects of PPIs |
GI disturbances (abdominal pain, nausea, vomiting, diarrhoea) Increased risk of gastric infections due to hypochlorhydria |
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MOA of PPIs |
Inhibit H/K ATPase on luminal surface of gastric parietal cells and therefore reduce gastric acid secretion |
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Monitoring needed for PPIs |
None |
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Drug interactions of PPIs |
PPIs are inducers of cytochrome P450 with some variation in potency between individual drugs and therefore may enhance effects of drugs metabolised in the liver |
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How long does it take for laxatives to take effect |
2-3 days for bulking of osmotic laxatives |
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Indications for PPIs |
Gastric/duodenal ulcers As part of the triple therapy for eradication of H pylori Gastro - oesophageal reflux disease Acid - related dyspepsia Hyper - secretory conditions, including Zollinger-Ellison syndrome Prevention and treatment of NSAID associated ulcers |
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Contraindications of PPIs |
Hypersensitiviy If red flag features of malignancy, need to investigate prior to initiating treatment |
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PPIS vs H2 antagonists |
PPIs reduce gastric acid secretion by >90% and H2 antagonists reduce by 50-60% making PPIs more effective at healing peptic ulcers |
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Special used of PPIs |
IV PPIs can be used in the management of acute upper GI bleeds |
