Clinical Pharmacology of Alimentary Flashcards
What are the common drugs used for acid suppression?
Antacids
H2-receptor antagonists
Proton pump inhibitors
What are the drugs that affect GI motility?
Anti-emetics
Anti-muscarinics/other anti-spasmodics
Anti-motility
What are common drugs used for IBD?
Aminosalicyclates
Corticosteroids
Immunosuppressants
Biologics
What are drugs affecting intestinal secretions?
Bile acid sequestrants
Ursodeoxycholic acid
What role do antacids have in acid suppression?
Contain Mg or Al
Neutralise gastric acid
Taken when symptoms occur
What role do alginates have in acid suppression?
Forms a viscous gel that floats on stomach contents and reduces reflux
What role do H2-receptor antagonists have on acid suppression?
Block histamine receptor thereby reducing acid secretion
Indicated in GORD/peptic ulcer disease
GIven orally/IV
What role does proton pump inhibitor play in acid suppression?
Block proton pump and thereby reduce acid secretion
Indicated in GORD/peptic ulcer disease
Oral/IV
What effect does prokinetic agents have on gut motility?
Increases gut motility + gastric emptying
Involves PNS control of smooth muscle + sphincter tone (via ACh)
How does domperidone work?
Blocks dopamine receptors which inhibit post-synaptic cholinergic neurones
What causes stimulation of the vomiting centre in the medulla?
Cerebral cortex (sight, smell etc)
Vestibular nuclei (motion)
Pharynx + GIT (gastroenteritis/radiotherapy/drugs)
Chemoreceptor trigger zone (drugs/toxins)
How do drugs that decrease motility work?
Via opiate receptors in GIT to decrease ACh release
Decreases smooth muscle contraction + increases anal sphincter tone
Why does loperamide have few central opiate effects?
Not well absorbed across BBB
What are the 3 mechanisms of anti-spasmodics?
Anti-cholinergic muscarinic antagonists = inhibit smooth muscle constriction in gut wall
Direct smooth muscle relaxants
CCBs reduce Ca required for smooth muscle contraction
What are 4 types of laxatives?
Bulk Osmotic Stimulant Softeners Either work by increasing bulk or drawing fluid into gut
What are the issues of laxatives?
Obstruction
Route of administration (oral or rectal)
Need for other measures = osmotic laxatives will not work without adequate fluid intake
Misuse
What are aminosalicylates?
Anti-inflammatory
Oral or rectal administration
Adverse effects - GI upset, blood dyscrasias, renal impairment
What are corticosteroids?
Anti-inflammatory effects
Given orally/IV/rectally
Concerns = osteoporosis, Cushingoid features, increased chance of infection, Addisonian crisis with abrupt withdrawal
Cannot be used long term
What are immunosuppressants?
Prevents formation of purines needed for DNA synthesis = reduces immune cell proliferation
Adverse effects = bone marrow suppression, azathioprine hypersensitivity, organ damage
What are biologics?
Prevents action of TNFa (cytokine in inflammatory response
Addresses inflammatory response but not underlying disease
What are the cautions/contraindications of Infliximab?
Current TB or other serious infection
MS
Pregnancy/breast feeding
What are the adverse effects of infliximab?
Risk of infection
Infusion reaction (fever, itch)
Anaemia, thrombocytopenia, neutropenia
Malignancy
What is cholestyramine?
Reduces bile salts by binding with them in the gut and the excreting as insoluble complex
May affect absorption of other drugs (taken separately)
May decrease Vitamin K
What is Ursodeoxycholic acid?
Used to treat gallstones and primary biliary cirrhosis
Inhibits enzyme involved in formation of cholesterol, alters bile level and slowly dissolves non-calcified stones
What drug processes can be affected by GI or liver disease?
Absorption
Distribution
Metabolism
Excretion
What causes diarrhoea/constipation?
Acute/chronic
Drugs (NSAIDs, antimicrobials etc)
What causes GI bleeding/ulceration?
Low dose aspirin/NSAIDs
What are changes to gut bacteria caused by? + effects
Mainly antibiotics
Loss of OCP activity
Reduced vitamin K absorption
Overgrowth of pathogenic bacteria
What is type A ADR in drug induced liver injury?
Intrinsic hepatotoxicity
Predictable, dose-dependent, acute)
What is type B ADR in drug induced liver injury?
Idiosyncratic hepatotoxicity
Unpredictable, not dose dependent
May occur at any time
What are the risk factors for ADR?
Age (elderly at risk) Sex (females at risk) Alcohol consumption Genetic factors Malnourishment
