Alimentary Pharmacology Flashcards
What are the main roles of drugs used for alimentary disease?
Acid suppression GI motility Laxatives IBD Intestinal secretion
How do H2 antagonists block acid production?
Blocking the H2 histamine receptor which stimulates proton pump activity
How do PPIs block acid production?
Directly blocking the activity of proton pumps
How do alginates work?
Form a viscous gel which floats on stomach contents and reduces reflux
How do antacids work?
Contain Mg or Al, neutralising stomach acid
When are H2 antagonists indicated?
GORD, Peptic ulcer
When are PPIs indicated?
GORD, Peptic ulcer
H. pylori (triple therapy)
PPIs are associated with what side effects?
Hypomagnesaemia
B12 Deficiency
? C. diff infection
What is the function of prokinetic agents?
Increased gut motility, gastric emptying
Give an example of H2 antagonists?
Ranitidine
Which drugs directly inhibit the vomiting centre of the medulla?
Anti-muscarinics
Anti-histamines
Which drugs inhibit vomiting via the Chemoreceptor trigger zone?
Dopamine antagonists
5HT3 antagonists
Cannabinoids
Which drugs decrease gastric motility?
Loperamide
Opioids
By what mechanism do anti-diarrhoea drugs have their effect?
Opioid receptors in GIT, decrease ACh release
Why does Loperamide have few central opioid effects?
Not well absorbed across the blood-brain barrier
What are anti-spasmodics?
Reduction of symptoms of IBS and renal colic
What are the mechanisms of anti-spasmodic drugs?
Muscarinic antagonists
Direct smooth muscle relaxants
CCBs
What are the 4 types of laxative?
Bulk
Osmotic
Stimulant
Softener
What are the main drugs used in IBD?
Aminosalicylates
Corticosteroids
Immunosuppressants
Biologics
How are aminosalicylates administered? When are they contraindicated?
Oral/rectal
Renal impairment
Allergy
What are the adverse effects associated with use of aminosalicylates?
GI upset
Renal impairment
Acute pancreatitis
What is associated with abrupt withdrawal of corticosteroids?
Addisonian Crisis
acute cortisol insufficiency
What are the contraindications/concerns with corticosteroids?
Osteoporosis
Cushingoid features
Infection susceptibility
How do immunosuppressants work to reduce the symptoms of IBD?
Prevent purine formation required for DNA synthesis - reduced immune cell proliferation
What are the adverse effects of immunosuppressants?
Azathioprine hypersensitivity
Bone marrow suppression
Organ damage
How do biologics work in treatment of IBD?
Anti- TNFa (proinflammatory cytokine)
Only treat inflammatory response
What biologic is commonly used in IBD?
Infliximab
When is Infliximab contraindicated?
Current TB, serious infection
MS
Pregnancy/breast feeding
What are the adverse effects of Infliximab?
Increased infection risk
Infusion reaction
Anaemia
Malignancy
When do biologics increase the risk of malignancy
Crohn’s disease
Which drugs affect biliary secretion?
Cholestyramine
Ursodeoxycholic Acid
For what is Cholestyramine indicated?
Patients presenting with pruritis due to biliary cause
What is the mechanism of Cholestyramine?
Reduced bile salts, binds them in gut and excretes as insoluble complex
What is a risk associated with use of Cholestyramine?
May effect the absorption of other drugs and fat soluble vitamins (inc. Vit K)
When is Ursodeoxycholic acid indicated?
Gallstones
Primary Biliary Cirrhosis
How does Ursodeoxycholic acid work?
Inhibits enzyme in formation of cholesterol, slowly dissolving NON-CALCIFIED stones
How may GI issues cause changes in drug distribution?
Low albumin causes a decrease in the amount of bound drug (more free drug)
How may GI issues cause changes in drug absorption?
Changes:
pH
Gut length
Transit time
How may GI issues cause changes in drug metabolism?
Liver enzymes, blood flow
Increased gut flora
Gut wall metabolism
How may GI issues cause changes in drug excretion?
Biliary excretion impairment (can increase toxicity)
What is the largest cause of drug-induced diarrhoea?
Antimicrobials
What are the most common GI adverse effects of medication?
GI upset
GI bleed/ulceration
Changes to gut flora
Induced Liver injury
What are the risk factors for GI adverse drug effects?
Female Elderly Alcoholics Malnourishment ?Genetics
Changes to gut bacteria due to adverse drug effects may cause what?
Reduced Vit K absorption (increased INR)
Overgrowth of pathogenic bacteria (C. diff)
What is the difference between type A and B drug induced liver injury (hepatotoxicity)?
A: Intrinsic - predictable, dose-dependent, acute
B: Idiosyncratic - unpredictable
Idiosyncratic hepatotoxicity mostly presents as what?
Hepatitis
Cholestasis
How is liver disease classified?
Child-Pugh classification
What must be taken into consideration when prescribing to a patient with liver disease?
Hepatotoxic drugs
Encephalopathic drugs
Drugs which change pharmacokinetics
Why must care be taken when prescribing warfarin in liver disease?
Clotting factors will likely already be low
Why must care be taken when prescribing aspirin/NSAIDs in liver disease?
Can increase bleeding time
NSAIDs can worsen ascites
Why must care be taken when prescribing Opiates/benzos in liver disease?
May precipitate encephalopathy
In a patient with Liver disease, which drugs should particular care be taken in prescribing?
Warfarin/Anti-coags
NSAIDs
Opiates/benzos