Alimentary Pharmacology Flashcards by Priyanka Bhandari

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

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What are examples of drugs for acid suppression?

Antacids

Alginates

H₂ receptor antagonists

Proton pump inhibitors

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What are examples of drugs affecting GI motility?

Anti-emetics

Anti-muscurinics/anti-spasmodics

Anti-motility

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What are examples of drugs for IBD?

Aminosalicylates

Corticosteroids

Immunosteroids

Biologics

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What are examples of drugs affecting intestinal secretions?

Bile acid sequestrants

Ursadeoxycholic acid

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What do antacids contain?

Magnesium or aluminium

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What do antacids do?

Neutralise gastric acid

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When are antacids taken?

When symptoms occur

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What is an example of an alginate?

Gaviscon

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What is an alginate?

Form of viscous gel that floats on stomach contents and reduces influx

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How do H₂ receptor antagonists work?

Block histamine receptor therby reducing acid secretion

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How are H₂ receptor antagonists administered?

Orally or IV

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What is an example of a H₂ receptor antagonist?

Ranitidine

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What is an example of a proton pump inhibitor?

Omeprazole

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When are H₂ receptor antagonists indicated?

GORD

Peptic ulcer disease

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How do proton pump inhibitors work?

Block proton pump and therby reduce acid secretion

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When are proton pump inhibitors indicated?

GORD

Peptic ulcer disease

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How are proton pump inhibitors administered?

Oral or IV

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What are side effects of proton pump inhibitors?

GI upset

Predisposition to C. Difficile infection

Hypomagnesaemia

B₁₂ deficiency

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What do prokinetic agents do?

Increase gut motility and gastric emptying

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What are examples of prokinetics?

Anti-emetics such as Metoclopramide and Domperidone

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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)

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What is the mechanism of action for Domperidone?

Blocks dopamine receptors which inhibit post-synaptic cholinergic neurones

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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

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

Explain Child-Pugh classification?

Individual scores are summed and then groups as A, B or C

What things does Child-Pugh classification consider?

Bilirubin (umol/L) Albumin (g/L) PT (s prolonged) Encephalopathy Ascites

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