Alimentary Pharmacology Flashcards
What are different categories of drugs for alimentary disease?
Acid suppression
Drugs affecting GI motility
Laxatives
Drugs for inflammatory bowel disease
Drugs affecting intestinal secretions
What are examples of drugs for acid suppression?
Antacids
Alginates
H2 receptor antagonists
Proton pump inhibitors
What are examples of drugs affecting GI motility?
Anti-emetics
Anti-muscurinics/anti-spasmodics
Anti-motility
What are examples of drugs for IBD?
Aminosalicylates
Corticosteroids
Immunosteroids
Biologics
What are examples of drugs affecting intestinal secretions?
Bile acid sequestrants
Ursadeoxycholic acid
What do antacids contain?
Magnesium or aluminium
What do antacids do?
Neutralise gastric acid
When are antacids taken?
When symptoms occur
What is an example of an alginate?
Gaviscon
What is an alginate?
Form of viscous gel that floats on stomach contents and reduces influx
How do H2 receptor antagonists work?
Block histamine receptor therby reducing acid secretion
How are H2 receptor antagonists administered?
Orally or IV
What is an example of a H2 receptor antagonist?
Ranitidine
What is an example of a proton pump inhibitor?
Omeprazole
When are H2 receptor antagonists indicated?
GORD
Peptic ulcer disease
How do proton pump inhibitors work?
Block proton pump and therby reduce acid secretion
When are proton pump inhibitors indicated?
GORD
Peptic ulcer disease
How are proton pump inhibitors administered?
Oral or IV
What are side effects of proton pump inhibitors?
GI upset
Predisposition to C. Difficile infection
Hypomagnesaemia
B12 deficiency
What do prokinetic agents do?
Increase gut motility and gastric emptying
What are examples of prokinetics?
Anti-emetics such as Metoclopramide and Domperidone
What is the mechanism of action of prokinetic agents?
Not clear but involves parasympathetic nervous sytem control of smooth muscle and sphincter tone (via acetylcholine)
What is the mechanism of action for Domperidone?
Blocks dopamine receptors which inhibit post-synaptic cholinergic neurones
What is the physiology behind vomiting?
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What different things can be targeted to prevent vomiting?
Chemoreceptor trigger zone
Pharynx and GIT
Vestibular neclei
Cerebral cortex
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What is a possible side effect of drugs that decrease motility?
Constipation
What are examples of drugs that decrease motility?
Loperamide
Opiods
What is the clinical benefit of drugs that reduce motility?
Anti-diarrhoea
What is the mechanism of action of drugs that decrease motility?
Decrease smooth muscle contraction, increase anal sphincter tone
What are anti-spasmodics used for?
Reduce symptoms due to IBS or renal colic
What are the 3 mechanisms of anti-spasmodics?
Anti-cholinergic muscurinic antagonists (inhibit smooth muscle contraction in the gut wall)
Direct smooth muscle relaxants
Calcium channel blockers reduce calcium required for smooth muscle contraction
Why does Loperamide have few central opiate effects?
Not well absorbed across the blood brain barrier
What are the 4 types of laxitives?
Bulk
Osmotic
Stimulant
Softeners
What is an example of a bulk laxative?
Isphagula
What is an example of an osmotic laxative?
Lactulose
What is an example of a stimulant laxative?
Senna
What is an example of a softener laxative?
Arachis oil
How do laxatives work?
By increasing bulk or drawing fluid into the gut
What are some issues with laxatives?
Obstruction
Route of administration (oral or rectal)
Need for other measures (osmotoc laxatives will not work without adequate fluid intake)
Misuse
What are examples of aminosalicylates?
Mesalazine
Olsalazine
What is the mechanism of action of aminosalicylates?
Unclear but is anti-inflammatory
What is the administration of aminosalicylates?
Oral or rectal
When should you be cautious towards the use of aminosalicylates?
In renal impairment
What are some adverse effects of aminosalicylates?
GI upset
Blood dyscrasias
Renal impairment
What effect do corticosteroids have?
Anti-inflammatory
What is the administration of corticosteroids?
Orally
IV
Rectal
What are contraindications for corticosteroids?
Osteoporosis
Cushingoid features including weight gain, DM, HT
Increased susceptability to infection
What is the mechanism of Azathioprine (immunosuppressent)?
Prevents the formation of purines required for DNA synthesis so reduces immune cell proliferation
What are adverse effects of Azathioprine?
Bone marrow suppresion
Azathioprine hypersensitivity
Organ damage (lung, liver, pancreas)
What are biologics?
Anti-TNFa antibodies
What are examples of biologics?
Infliximab
Certolizumab
Adalimumab
Natalizumab
Golimumab
Vedolizumab
What are contraindications to Infliximab?
Current TB or other serious infection
MS
Pregnancy/breast feeding
What are adverse effects of Infliximab?
Risk of infection, particular TB
Infusion reaction (fever, itch)
Anaemia, thrombocytopenia, neutropenia
Malignancy
What is TNFa?
Key cytokine in inflammatory response
What is the mechanism of Cholestyramine?
Reduces bile salts by binding with them in the gut and then excreting as insoluble complex
What are side effects of Cholestyramine?
May affect fat soluble vitamin absorption so may decrease vitamin K levels (affecting clotting and warfarin)
What are indications for Ursodeoxycholic acid?
Gallstones and primary biliary cirrhosis (PBC)
What is the mechanism of action of Ursodeoxycholic acid?
Inhibits an enzyme involved in the formation of cholesterol, altering amount in bile and slowly dissolving non-calcified stones
What does ADME stand for?
Absorption
Distribution
Metabolism
Excretion
Diseases of what systems can affect the processes of a drug?
GI or liver diseases
How can GI diseases impact administration of a drug?
May require the route of administration to be changed
What is absorption of a drug impacted by?
pH
Gut length
Transit time
What is distribution of a drug impacted by?
Low albumin (decreased binding and increased free drug concentration)
What is metabolism of a drug impacted by?
Liver enzymes
Increased gut bacteria
Gut wall absorption
Liver blood flow
What is excretion of drugs impacted by?
Biliary excretion (increased toxicity if hepatobiliary disease)
What impact does liver disease have on pharmacodynamic effects?
Exaggerated or reduced response
Increased toxocity
What are examples of adverse GI effects caused by drugs?
GI upset
Diarrhoea
Constipation
GI bleeding/ulceration
Changes to gut bacteria
Drug induced liver injury
How common is GI upset with medication?
Very common, 20-40% of all adverse drug reactions (ADRs)
What are examples of drugs that can cause diarrhoea or constipation as an adverse effect?
Cholinergics
NSAIDs
Antimicrobials
Opiates
Anticholinergics
What are different mechanisms of drugs cause diarrhoea/constipation as an adverse effect?
Osmotic
Secretory
Shortened transit time
Protein losing
Malabsorption
What are examples of drugs that cause GI bleeding/ulceration as a side effect?
1) Low dose aspirin/NSAIDs
3) Warfarin
How do NSAIDs lead to bleeding?
Cause mucosal injury and bleeding through COX-1 and COX-2 receptors, and epithelial damage
What drugs can cause changes to gut bacteria as a side effect?
Mainly antibiotics
What does changes to gut bacteria as a side effect cause?
Loss of OCP activity
Reduced vitamin K absorption (increased prothrombin time)
Overgrowth of pathogenic bacteria (such as C. Difficile)
What are the different categories of drug induced liver injury?
Intrinsic hepatotoxicity
Idiosyncratic hepatotoxicity
What kind of adverse drug reaction is intrinsic hepatotoxicity?
Type A ADR
What can be said about dose and predictability of intrinsic hepatotoxicity ADRs?
Predictable, dose dependent
What can be said about the dose and predictability of idiosyncratic hepatotoxicity?
Unpredictable, not dose dependent
What kind of adverse drug reaction is idiosyncratic hepatotoxicity?
Type B ADR
What are examples of diseases that can be caused by drugs?
Acute hepatitis
Chronic hepatitis
Acute cholestasis
Mixed pattern or atypical hepatitis
Nonalcoholic steatohepatitis
Fibrosis/cirrhosis
Microvesicular steatosis
Veno-occlusive disease
What are risk factors for adverse drug reactions?
Age (elderly at risk)
Sex (female at risk)
Alcohol consumption
Genetic factors
Malnourishment
What is the most common reason for medicinial products being withdrawn from the market?
Hepatotoxicity
What classification is used to measure the severity of liver disease?
Child-Pugh classification
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Explain Child-Pugh classification?
Individual scores are summed and then groups as A, B or C
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What things does Child-Pugh classification consider?
Bilirubin (umol/L)
Albumin (g/L)
PT (s prolonged)
Encephalopathy
Ascites
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Whilst prescribing in liver disease, care must be taken with what?
Drugs which can be toxic due to changes in pharmacokinetics
Drugs which are hepatotoxic
Drugs which may worsen the non-liver aspects of liver disease (such as encephalopathy)
What are particular drugs that are known to cause problems with liver disease?
Warfarin/anti-coagulant (clotting factors are already low)
Aspirin/NSAIDs (increase bleeding time in combination with deficiency in clotting factors)
Opiates/benzodiazepines (may precipitate encephalopathy by increasing sedation)
Where can patients find more drug information?
BNF guidance on drugs in liver disease