Clinical GI pharmacology Flashcards
This covers drugs for:
Acid Suppression Motility Laxatives IBD Medications Drugs affecting secretions
What drug types are used for acid suppression?
Antacids - Neutralize acid
H2-receptor antagonists - Block histamine2 receptor
Proton pump inhibitors - Block pumping out of H+ ions.
What are the types of antacid?
Most contain Mg or Al and function by neutralizing gastric acid.
Alginates arnt like the rest, they form a viscous gel floating on the stomach contents which prevents reflux. (Gaviscon)
Example of a H2-receptor antagonist?
Ranitidine
Oral or IV
Give an example of a proton pump inhibitor and when theyre used?
Omeprazole
Oral or IV
Theyre used for GORD, peptic ulcer disease and as triple therapy with 2 antibiotics for Peptic/duodenal ulcers associated with H pylori.
What are the risks of PPIs?
Predispose to:
- C. Diff infection
- Hypomagnesaemia
- B12 Deficiency
What are the types of drugs affecting gut motility?
- Anti-emetics
- Anti-spasmodics (inc. Anti-muscarinics)
- Anti-motility
- Pro-kinetic
What are the types of anti-spasmodics used for GI motiltiy?
- Anti-cholinergic muscarinic antagonists
- Direct smooth muscle relaxants
- Ca channel blockers (lowers Ca for muscle contraction)
How do anti-motility drugs work?
Loperamide (immodium) or opioids
They activate opiate receptors to inhibit Ach release. This in turn lowers smooth muscle contraction and raises anal sphincter tone.
Look out they can cause constipation.
How do anti-emetics help with GI issues?
They are prokinetic agents, i.e. they increase gut motility
& gastric emptying.
Probably by blocking the dopamine receptors that inhibit post-synaptic cholinergic receptors. (A roundabout way of stimulating cholinergic receptors to increase smooth muscle contraction)
E.g. Domperidone (a dopamine antagonist).
What are the categories of laxative?
Bulk e.g. Isphagula - Draws in water leading to bulkier stool which stimulates a bowel movement
Osmotic e.g. Lactulose - Helps the intestine retain water to soften and bulk the stool
Stimulant e.g. Senna - Directly stimulates gut motility
Softeners e.g. Arachis Oil - Softens faeces
List the drugs for IBD
- Aminosalicylates e.g. Mesalazine
- Corticosteroids e.g. Prednisalone
- Immunsuppresants e.g. Azathioprine
- Biologics e.g. Anti-TNFalpha antibodies Infliximab
What are the side effects of corticosteroids?
Fucking loads incl:
- Osteoporosis
- Cushing’s Disease
- Predispose to infection
- Addisonian crisis on abrupt withdrawel
How does azathioprine work?
Prevent purine formation needed to make DNA thus reducing immune cell proliferation
How does Anti-TNFalpha Antibodies work??
By inhibiting the action of TNFalpha which is a key cytokine of inflammation