Clinical Pharmacology of Alimentary

Question 1

What are the main drug classes used in the treatment of alimentary disease?

Answer 1

Antacids
Alginates
Other mucosal protectors
H2 Receptor antagonists 
Proton pump inhibitors

Question 2

What is the purpose of antacids?

Answer 2

Neutralise gastric acids when symptoms occurs

Question 3

What is the purpose of alginates?

Answer 3

Reduces reflux by forming a viscous gel that floats on the stomach contents

Question 4

What is the purpose of H2 receptor antagonists?

Answer 4

Block histamine receptors to decrease acid secretion

Has GI side effects

Question 5

What is the purpose of Proton pump inhibitors?

Answer 5

Block proton pump

Question 6

What drug types affect motility?

Answer 6

Anti-emetics
Anti-muscarinics/other anti-spasmodics
Anti-motility

Question 7

What is renal colic?

Answer 7

Kidney stones move to the ureter

Question 8

In what way do the three mechanisms help to reduce GORD symptoms?

Answer 8

1. Anti-cholinergic muscarinic antagonists (Hyoscine (Buscopan) & Mebeverine) inhibit smooth muscle constriction in the gut wall, producing muscle relaxation and reduction spasm
2. Smooth muscle relaxants
3. Calcium-channel blockers (pep permint oil) reduce calcium required for smooth muscle contraction

Question 9

What are the four types of laxatives?

Answer 9

Bulk - Isphagula
Osmotic - Lactulose
Stimulant - Senna
Softeners - Arachis oil

Question 10

What are the issues with laxatives?

Answer 10

Obstruction
Route of administration
Need for other measures
Misuse

Question 11

What drugs are used for IBD?

Answer 11

Aminosalicylates
Corticosteroids
Immunosuppressants
Biologics
*First two are anti-inflammatory*

Question 12

What do immunosuppressants do?

Answer 12

Prevents the formation of purines required for DNA synthesis so reduces immune cell proliferation

Question 13

What do biologics do?

Answer 13

Prevents action of TNfα (Key cytokine in inflammatory response) so addresses the response but not the underlying disease process

Question 14

What are the contraindications to infliximab?

Answer 14

Current TB or other serious infection
MS
Pregnancy/breast feeding

Question 15

What are the adverse effects of infliximab?

Answer 15

Infection risk
Infusion reaction - Fever/Itch
Anaemia/Thrombocytopenia/Neutropenia
?Demyelination

Question 16

What two drugs affect biliary secretions?

Answer 16

Cholestyramine

Ursodeoxycholic acid

Question 17

What does cholesytramine do?

Answer 17

Pruritis from biliary cause and reduces bile salts by binding with them in the gut and then excreting as an insoluble complex May decrease vitamin K levels and should be taken separately to any other drugs

Question 18

What does Ursodeoxycholic acid do?

Answer 18

Used for Gallstones and Primary Biliary Cirrhosis and it inhibits an enzyme involved in the formation of cholesterols, altering amount in bile and slowly dissolving non-calcified stones

Question 19

What is the problem with gastrointestinal or liver disease?

Answer 19

It can affect the processes of drug absorption, distribution, metabolism and excretion so GI symptoms may also necessitate a change in route of administration

Question 20

How can distribution be affected?

Answer 20

Low albumin

Question 21

How can metabolism be affected?

Answer 21

Increased gut bacteria can cause increased metabolism
Gut wall metabolism leading to a disease reducing first pass metabolism e.g. Morphine
Liver enzymes have variable effects but generally toxicity
Liver blood flow as some drugs have a high extraction ratio

Question 22

How can excretion of drugs be affected?

Answer 22

Biliary excretion results in an increased toxicity if a patient has hepatobiliary disease e.g. Spironolactone Look at lecture notes

Question 23

What are the adverse effects of GI drugs? (4)

Answer 23

GI upset
Diarrhoea/Constipation - Acute or Chornic e.g. NSAIDs
GI Bleeding/Ulceration - Most commonly due to a low dose os aspirin
Changes to gut bacteria

Question 24

How do changes in gut bacteria occur?

Answer 24

Mainly antibiotics causing a reduced a vitamin K absorption which caused an increased prothrombin time (Increased time for blood to clot)

Question 25

What are the three types of drug induced liver injury?

Answer 25

Type A ADR (Intrinsic Hepatoxocity)
Type B ADR (Idiosyncratic Hepatoxocity)
Drug itself or an active metabolite

Question 26

How can a type A ADR be determined?

Answer 26

Predictable
Dose-dependent
Acute

Question 27

How can a type B ADR be determined?

Answer 27

Unpredictable
Not dose-dependent
Can occur at any time

Question 28

What classification is used to assess the severity of Liver Disease?

Answer 28

Child-Pugh classificaiton

A = 9

Question 29

What types of drugs should be avoided?

Answer 29

Drugs that are toxic due to many changes in pharmacokinetics
Hepatotoxic e.g. Methotrexate
Going to worsen the non-liver aspects of liver disease e.g. Ascites & Encephalopathy from Benzodiazepines

Question 30

What drugs should you be careful of?

Answer 30

Warfarin/Anti-coagulants – Clotting factors are already low in liver disease
Aspirin/NSAIDs – Can increase bleeding time/NSAIDs can worse ascites due to fluid retention Opiates/Benzodiazepines – May precipitate encephalopathy by increasing sedation