NURS 8024 (Medicine) Advanced
Pharmacology Definitions and Concepts
Week 1 Summary A+ GRADED.
Competition for Plasma Protein Binding: Class II (minority of drugs)
✔✔-High dose/capacity ratio
-Amount of drug > albumin binding capacity
-High proportion of drug in "free" state = not protein bound
Clinical Implications of Plasma Protein Binding
✔✔Drug displacement from albumin substantial
source of drug interactions.....
• Class I drug - warfarin
• Highly protein bound - small fraction of free drug in plasma
↓
• Class II drug given - sulfa
• Displaces warfarin from albumin
• Rapid rise in free drug concentration
• Increased therapeutic effect- toxic effect
Drug Displacement and Vd
✔✔--Dependent on Vd and therapeutic index of drug
--Large Vd verses small Vd (drug is less around)
,What is the therapeutic index (TI)?
✔✔Ratio of a drug's toxic level to the level that provides therapeutic
benefits--Measure of drug safety--Safer Drug has a higher TI
--If the Therapeutic Index is narrow--small increase in drug
concentration can have a substantial clinical impact Ex: Digoxin (the
closer the ratio is to 1 the less safe the drug)
What are the components of calculation of TI? Toxic dose for 50 % of
people divided by the effective does for 50% of people). Therapeutic Dose
Divided by the Lethal Dose : TI = TD50 Divided by ED50
Drug Metabolism-First Order Kinetics (most drugs)
✔✔--Metabolic transformation of drugs by enzymes
--Rate of drug metabolism is directly proportional to the concentration of
free drug--so CONSTANT FRACTION of drug per unit of time is
eliminated
--Linear elimination pattern: reflected by 1/2 life of the drug
--Each half life cuts the drug concentration by 50%
At 2 Half lives= drug has been 75% removed
At 5 Half lives= drug is essentially removed from the body
--has a CURVED ELIMINATION LINE ON GRAPH
Drug Metabolism -- Zero Order Kinetics (minority of drugs)
✔✔ASA, Ethanol, Phenytoin
Rate of metabolism is constant OVER TIME---therefore a CONSTANT
AMOUNT of drug is metabolized per unit of TIME
--HAS A STRAIGHT ELIMINATION LINE ON GRAPH
, Process of Drug Metabolism
✔✔Phase 1 and Phase 2
Phase 1: increase polarity and water solubility of the drug (oxidation and
hydrolysis)
Phase 2: Involves conjugation: Increase solubility and facilitates secretion
of the metabolite from the body
--Some drugs undergo phase 1 and 2 metabolism
--Some drugs only undergo one of the phases--dependent on the
chemical nature of the drug
Kidneys filter more water soluble drugs; Liver filters more lipid soluble
drugs
Phase 1 drug metabolism
✔✔Oxidation, reduction, hydrolysis
https://www.nottingham.ac.uk/nmp/sonet/rlos/bioproc/liverdrug/pag
e_two.html
Phase 2 drug metabolism
✔✔Involves Conjugation (the attachment of an ionized group to the
drug)
--increases solubility, facilitates excretion from the body
https://www.nottingham.ac.uk/nmp/sonet/rlos/bioproc/liverdrug/pag
e_two.html
Lipid Soluble drug and phase 2 metabolism
✔✔Phase 2 happens first then phase 1 for a lipid soluble drug--it will be
eliminated after phase 1
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller AcademicAllure. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £13.20. You're not tied to anything after your purchase.