Clinical Pharmacology of Alimentary Flashcards
What are the main drug classes used in the treatment of alimentary disease?
Antacids Alginates Other mucosal protectors H2 Receptor antagonists Proton pump inhibitors
What is the purpose of antacids?
Neutralise gastric acids when symptoms occurs
What is the purpose of alginates?
Reduces reflux by forming a viscous gel that floats on the stomach contents
What is the purpose of H2 receptor antagonists?
Block histamine receptors to decrease acid secretion
Has GI side effects
What is the purpose of Proton pump inhibitors?
Block proton pump
What drug types affect motility?
Anti-emetics
Anti-muscarinics/other anti-spasmodics
Anti-motility
What is renal colic?
Kidney stones move to the ureter
In what way do the three mechanisms help to reduce GORD symptoms?
- Anti-cholinergic muscarinic antagonists (Hyoscine (Buscopan) & Mebeverine) inhibit smooth muscle constriction in the gut wall, producing muscle relaxation and reduction spasm
- Smooth muscle relaxants
- Calcium-channel blockers (pep permint oil) reduce calcium required for smooth muscle contraction
What are the four types of laxatives?
Bulk - Isphagula
Osmotic - Lactulose
Stimulant - Senna
Softeners - Arachis oil
What are the issues with laxatives?
Obstruction
Route of administration
Need for other measures
Misuse
What drugs are used for IBD?
Aminosalicylates Corticosteroids Immunosuppressants Biologics *First two are anti-inflammatory*
What do immunosuppressants do?
Prevents the formation of purines required for DNA synthesis so reduces immune cell proliferation
What do biologics do?
Prevents action of TNfα (Key cytokine in inflammatory response) so addresses the response but not the underlying disease process
What are the contraindications to infliximab?
Current TB or other serious infection
MS
Pregnancy/breast feeding
What are the adverse effects of infliximab?
Infection risk
Infusion reaction - Fever/Itch
Anaemia/Thrombocytopenia/Neutropenia
?Demyelination
What two drugs affect biliary secretions?
Cholestyramine
Ursodeoxycholic acid
What does cholesytramine do?
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
What does Ursodeoxycholic acid do?
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
What is the problem with gastrointestinal or liver disease?
It can affect the processes of drug absorption, distribution, metabolism and excretion so GI symptoms may also necessitate a change in route of administration
How can distribution be affected?
Low albumin
How can metabolism be affected?
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
How can excretion of drugs be affected?
Biliary excretion results in an increased toxicity if a patient has hepatobiliary disease e.g. Spironolactone Look at lecture notes
What are the adverse effects of GI drugs? (4)
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
How do changes in gut bacteria occur?
Mainly antibiotics causing a reduced a vitamin K absorption which caused an increased prothrombin time (Increased time for blood to clot)
What are the three types of drug induced liver injury?
Type A ADR (Intrinsic Hepatoxocity)
Type B ADR (Idiosyncratic Hepatoxocity)
Drug itself or an active metabolite
How can a type A ADR be determined?
Predictable
Dose-dependent
Acute
How can a type B ADR be determined?
Unpredictable
Not dose-dependent
Can occur at any time
What classification is used to assess the severity of Liver Disease?
Child-Pugh classificaiton
A = 9
What types of drugs should be avoided?
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
What drugs should you be careful of?
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
