Pharmacology Flashcards
(26 cards)
Magnesium trisilicate, aluminium/magnesium mixtures (Maalox), alginates
Class: antacids and alginates.
MOA: increases pH of gastric acid via neutralisation reaction.
Indication: dyspepsia, GORD.
Side effects/contraindications: diarrhoea, nephrolithiasis.
Ranitidine
Class: H2 receptor antagonist.
MOA: block H2 histamine receptors, reducing gastric acid secretion.
Indication: dyspepsia, GORD, peptic ulcer, prophylaxis of NASID associated peptic ulceration.
Side effects/contraindications: generally well tolerated with few side effects. Diarrhoea, headache and dizziness. Warning - they disguise the symptoms of gastro-oesophageal cancer, so important to investigate cause. Dose reduced in renal impairment.
Lansoprazole, omeprazole, pantoprazole
Class: proton pump inhibitors (PPIs).
MOA: irreversibly inhibiting H+/K+ ATPase in gastric parietal cells, reducing gastric acid secretion. Suppress gastric acid secretion almost completely (unlike H2 antagonists).
Indication: peptic ulcers, prophylaxis of NSAID associated peptic ulcers, dyspepsia, GORD, eradication of H.pylori infection (in combination with antibiotics), oesophagitis.
Side effects/contraindications: GI disturbance, headache, increased risk of C.difficile infection. Prolonged treatment - hypomagnesaemia. Warning - disguise symptoms of gastro-oesophageal cancer, so important to investigate cause (e.g. weight loss, dysphagia). Increase risk of fracture in elderly. Omeprazole may interact with clopidogrel.
Codeine phosphate
Class: anti-motility/anti-diarrhoea.
MOA: mu opioid receptor agonist, decreases peristalsis.
Indication: IBS, viral gastroenteritis.
Side effects/contraindications: opioid toxicity and dependence.
Loperamide
Class: anti-motility/anti-diarrhoea.
MOA: mu opioid receptor agonist in the gut, reduces peristalsis, resulting in slowed transit time allowing more time for water absorption. Also increases anal sphincter tone. It has NO analgesic effects because it doesn’t penetrate CNS (so preferable over codeine).
Indication: IBS, viral gastroenteritis.
Side effects/contraindications: constipation, abdominal cramps and flatulence. Avoided in acute UC due to increased risk of megacolon and perforation. Also avoided in C.difficile colitis and acute bloody diarrhoea (dysentery).
Diphenoxylate (co-phenotrope)
Class: anti-motility/anti-diarrhoea.
MOA: mu opioid receptor agonist in gut, decreasing peristalsis, increasing water absorption.
Indication: rehydration in acute diarrhoea, control of faecal consistency after colostomy or ileostomy.
Side effects/contraindications: avoid antibiotic-associated colitis.
Kaolin
Class: water adsorbent/anti-diarrhoea.
MOA: adsorbs toxic molecules, binding agent.
Indication: acute diarrhoea.
Octreotide
Class: somatostatin analogue.
MOA: decreases amount of water in stool.
Indication: diarrhoea associated with carcinoid tumours.
Terlipressin
Class: vasopressin (ADH) analogue.
MOA: splanchnic vasoconstriction, reducing portal venous pressure.
Indication: oesophageal varices.
Methylcellulose
Class: bulk-forming laxative.
MOA: increase bulk of stools, stimulating stretch receptors. Faecal softener.
Indication: constipation.
Side effects/contraindications: flatulence, bloating and cramps.
Ispaghula husk
Class: bulk-forming laxative.
MOA: increases bulk of stool, stimulating stretch receptors.
Indication: constipation.
Side effects/contraindications: flatulence, bloating and cramps. Avoid in faecal impaction and intestinal obstruction.
Senna, bisacodyl, glycerol suppositories, docusate sodium
Class: stimulant laxative.
MOA: increase water and electrolyte secretion, increasing volume of colonic content, stimulating peristalsis and intestinal motility. Docusate also acts as faecal softener.
Indication: constipation, faecal impaction suppositories.
Side effects/contraindications: cramps, diarrhoea. Prolonged use - melanosis coli. Avoid in intestinal obstruction (increased risk of perforation).
Lactulose, macrogol, phosphate enema
Class: osmotic laxatives.
MOA: based on osmotically active substances that aren’t digested or absorbed, so they increase stool water content as water moves into bowel lumen via osmosis, stimulating peristalsis.
Indication: constipation, faecal impaction.
Side effects/contraindications: flatulence, cramps, nausea, diarrhoea. Avoid in intestinal obstruction.
Sodium picosulphate
Class: stimulant laxative.
MOA: stimulates mucosa increasing intestinal motility.
Indication: constipation.
Side effects/contraindications: diarrhoea, GI discomfort. Avoid in intestinal obstruction.
Mesalazine, sulfasalazine
Class: aminosalicylates.
MOA: release 5-ASA, which has anti-inflammatory and immunosuppressive effects acting topically on gut.
Indication: first line in treatment of mild-moderate UC (mesalazine).
Side effects/contraindications: GI upset (nausea, dyspepsia), headache, leukopenia, thrombocytopenia, renal impairment. Hypersensitivity reactions. Avoid in blood clotting abnormalities.
Metoclopramide
Class: antiemetic.
MOA: dopamine D2 receptor antagonist in chemoreceptor trigger zone and also promotes gastric emptying.
Indication: prophylaxis and treatment of N+V.
Side effects/contraindications: diarrhoea, EPS (acute dystonia). Avoid in intestinal obstruction and perforation (pro-kinetic effects). Avoid in Parkinson’s disease.
Cyclizine, promethazine
Class: antiemetic.
MOA: histamine H1 receptor antagonist, inhibiting vomiting centre in medulla. Also anti-muscarinic effects.
Indication: prophylaxis and treatment of N+V, particularly in motion sickness or vertigo.
Side effects/contraindications: drowsiness (cyclizine less sedating), dry throat and mouth, palpitations (IV injection). Avoid in hepatic encephalopathy and prostatic enlargement (urinary retention).
Ondansetron
Class: antiemetic.
MOA: serotonin 5-HT3 receptor antagonist, inhibiting chemoreceptor trigger zone in vomiting centre.
Indication: prophylaxis and treatment of N+V, particularly in general anaesthesia and chemotherapy.
Side effects/contraindications: constipation. Avoided in prolonged QT interval.
Hydrocortisone, prednisolone, budesonide
Class: corticosteroids.
MOA: bind cytosolic glucocorticoid receptors —> translocates to nucleus —> bind glucocorticoid-response elements —> gene expression —> up-regulate anti-inflammatory genes and down regulate pro-inflammatory genes.
Indication: suppression of IBD.
Side effects/contraindications: immuosuppression, diabetes, osteoporosis, proximal muscle weakness, skin thinning with easy bruising, mood and behavioural changes. Mineralocorticoid effects - hypertension, hypokalaemia, oedema. Prolonged treatment - adrenal atrophy. Increased risk of peptic ulcers and GI bleeding with NSAID use. Enhance hypokalaemia in patients taking beta 2 agonists, loop/thiazide diuretics.
Azathioprine
Class: immunosuppressant therapy.
MOA: pro-drug. The main metabolite inhibits purine synthesis —> inhibit DNA/RNA replication —> lymphocyte suppression.
Indication: maintenance of remission in CD and UC.
Side effects/contraindications: bone marrow suppression (leukopenia), nausea, hypersensitivity reactions (diarrhoea, vomiting, rash, fever, myalgia, hypotension, pancreatitis). Rare - veno-occlusive disease, hepatotoxicity, lymphoma. TPMT phenotyping before commencing therapy. Avoided in patients with absent TPMT activity and in pregnancy. Should not be prescribed with allopurinol.
Infliximab, adalimumab
Class: cytokine inhibitors (mAbs).
MOA: anti-TNF alpha —> inhibits pro-inflammatory cytokine signalling.
Indication: Crohn’s disease.
Side effects/contraindications: risk of agranulocytosis.
Hyoscine butylbromide (Buscopan)
Class: anti-spasmodic/anti-muscarinic.
MOA: competitively inhibit ACh —> reduce smooth muscle tone and peristaltic contractions.
Indication: IBS.
Side effects/contraindications: tachycardia, dry mouth, constipation, urinary retention in BPH, blurred vision. Avoid in patients at risk of arrhythmias.
Mebeverine, peppermint oil
Class: antispasmodics.
MOA: anticholinergic (mebeverine), relaxes GI smooth muscle by reducing calcium influx (peppermint oil).
Indication: IBS.
Side effects/contraindications: avoid mebeverine in paralytic ileus.
Nystatin, fluconazole
Class: anti-fungals.
MOA: polyene antifungals (nystatin) bind ergosterol in cell membrane, creating a pore which ions leak out of —> cell death. Triazole antifungals (fluconazole) inhibit ergosterol synthesis —> inhibits cell growth and replication.
Indication: GI infections.
Side effects/contraindications: GI upset, headache, hepatitis, rash (oral fluconazole).
