Adverse Drug Reactions Flashcards
Why might a patient take an incorrect dose of a drug?
Mistake in prescription by doctor
Pharmacist mistake in dispensing
Lack of patient compliance - fear of side effects
Misunderstanding of dosing instructions by patient
Addictions
Drug not absorbed due to interaction with food in the stomach
What do you think has caused the adverse drug reactions in Mr. Jones’ case?
Clarithromycin increases the anticoagulant effect of warfarin - effects breakdown via cytochrome p450 enzymes
Increased plasma concentration of warfarin
What is St. John’s wort?
Supplement that contains hyperforin (potential anti-depressant?)
What is INR?
international normalized ratio and is a standardised measure of blood clotting
How is INR measured?
Ratio of Prothrombin time to a control
Raised to the power of the ISI (international sensitivity index) value for the tissue factor used for the test
What does a fall in the INR signify?
Increased risk of thrombosis
What is the mechanism of actions of digoxin?
Reverses activity of the myocardial sodium-potassium pump
Acts on AV node
Competes with K for its binding site
What is the most important blood test?
Need to know plasma potassium
If the patient has hypokalaemia as it would enhance the action of digoxin
Hyperkalaemia could indicate kidney disease as there us reduced clearance and more digoxin
Why might the patient have become confused?
Lipid-soluble drugs increased half life in the elderly if they carry more fat
What is pharmockinetics?
What the body does to the drug
- absorbed
- distributed
- metabolised
- excreted
What is pharmacodynamics?
What the drug does to the body
What might the patients INR be increasing?
Metabolism of drugs affected by malnutrition
Malnutrition decreases plasma protein levels (warfarin is heavily plasma protein bound)
