Alimentary Pharmacology Flashcards
What drugs are used for acid suppression?
Antacids
Alginates
H2 receptor antagonists
Proton pump inhibitor
What drugs affect GI motility?
Anti-emetics
Anti-muscarinics (anti-spasmodics)
Anti-motility
What drugs are used in IBD?
Aminosalicylates
Corticosteroids
Immunosuppressants
Biologics
How do antacids work?
Neutralise gastric acid, contain Mg or Al (Maalox)
How do alginates work?
Form a viscous gel that frats on stomach contents, reduces reflux (Gaviscon)
How do H2 receptor antagonists work?
Block histamine receptor, reduces acid secretion
How are H2 receptor antagonists administered?
Oral or IV
How do proton pump inhibitors work?
Block proton pump (K+/H+ pump), reduces acid secretion
How are proton pump inhibitors given?
Oral or IV (Omeprazole)
What are the complications of proton pump inhibitors?
GI upset
Predisposition to c diff infection
Hypomagnesaemia
B12 deficiency
Name drugs which increase GI motility
Metoclopramide
Domperidone
How does domperidone affect GI motility?
Blocks dopamine receptors which inhibit post synaptic cholinergic neurones
Name drugs which decrease GI motility?
Loperamide
Opioids
How do loperamide and opioids work to decrease GI motility?
Action is via opiate receptors in GI tract to decrease ACh release, thereby muscle contraction
How do anti-spasmodics work to affect GI motility?
Anti cholinergic muscarinic antagonists inhibit smooth muscle constriction, producing muscle relaxation and reduction spasm
Smooth muscle relaxants
Calcium channel blockers reduce calcium required for muscle contraction
What are the 4 types of laxatives?
Bulk (Isphagula)
Osmotic (Lactulose)
Stimulant (Senna)
Softeners (Arachis oil)
How do laxatives work?
Increasing bulk, drawing fluid into gut and softening stool
What are the issues with laxatives?
Obstruction (can rupture colon)
Misue
What are the main aminosalicylates?
Mesalazine
Olsalazine
How are aminosalicylates administered?
Oral
Rectal
What are the adverse affects of aminosalicylates?
GI upset
Blood dyscrasia
Renal impairment
How are corticosteroids administered?
Oral
IV
Rectal
What are the contraindications of corticosteroids?
Osteoperosis
Cushingoid features (weight gain)
Increased susceptibility to infection
Addisonian crisis in abrupt withdrawal
How do immunosuppressants work in IBD?
Azathioprine
Prevent the formation of purines required for DNA synthesis, reduces immune cell proliferation
What are the adverse affects of immunosuppressants?
Bone marrow suppression
Azathioprine hypersensitivity
Organ damage (lung, liver, pancreas)
Numerous drug interactions
How do biologics work in IBD? (Inflixamab)
Prevents action of TNFalpha
What are the contraindications of Inflixamab?
Cannot be used when pregnant, breast feeding, have a serious infection, TB or multiple sclerosis
What are the adverse affects of Inflixamab?
Risk if infection Infusion reaction Anaemia Thrombocytopenia Neutropenia
What drugs are used to control biliary secretions?
Cholestyramine
Ursodeoxycholic acid
How does cholestyramine work to control biliary secretions?
Reduces bile salts by binding with them in the gut then excreting as an insoluble complex
What are the adverse affects of cholestyramine?
May affect absorption of other drugs
May affect fat soluble vitamin absorption, decrease levels of vitamin K her fore affecting clotting and warfarin
How does ursodeoxycholic acid work to control biliary secretions?
Inhibits enzyme involved in formation of cholesterol, altering amount in bile and slowly dissolving non calcified stones
What are the main gastrointestinal adverse affects due to drugs?
Diarrhoea Constipation Bleeding Ulceration Changes to gut bacteria Drug induced liver injury
What are the risk factors for drug administration?
Age (elderly) Sex (female) Alcohol consumption Genetic factors Malnourishment
