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Introduction to Pharmacology and Pharmacokinetics

Introduction to Pharmacology and Pharmacokinetics. Pharmacology 49.222 Bill Diehl-Jones RN, PhD Faculty of Nursing and Department of Zoology. Agenda. The instructor The course organization expectations/grading Introduction Purpose of drug therapy Principles of Pharmacokinetics.

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Introduction to Pharmacology and Pharmacokinetics

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  1. Introduction to Pharmacology and Pharmacokinetics Pharmacology 49.222 Bill Diehl-Jones RN, PhD Faculty of Nursing and Department of Zoology

  2. Agenda • The instructor • The course • organization • expectations/grading • Introduction • Purpose of drug therapy • Principles of Pharmacokinetics

  3. The Instructor • Office: 333 Helen Glass • Lab: 336 Helen Glass • Phone: 474-7136 • Email: • Bill_Diehl-Jones@umanitoba.ca • Office Hours: • by appointment

  4. The Course • Introductory level course designed for nursing students • Lecture notes are available on my website • Physiological and pharmacological principles will be integrated

  5. Optional Text • It is currently in the U of M bookstore • Primary text: • Lilly and Aucker, 2001

  6. Core Concepts Introduction to Pharmacology General Principles Pharmacotherapeutics The Role of the Nurse Drug Issues in Society

  7. Evaluation Methods • Mid Term Test - 25% • Final Exam - 35% • Patient Information Pamphlet - 20% • Pop Quizzes (x 4) - 10% • Test/exam will be multiple choice, true false and matching

  8. Why Do We Study Pharmacology? • A. It’s good for you • B. You will be able to use fancy terms like ’bioavailabilty’ • C. My instructor likes torture • D. A competent nurse must understand why his/her patient is getting a medication, and HOW IT WORKS

  9. Purpose of Drug Therapy • “… to prevent, control or cure various disease states.” • To achieve this, the right drug dose must be delivered to the tissues • Every nurse must know… • speed of onset of drug action • intensity of drug effect • duration of drug action

  10. A Graphical Example: Lethal Dose Drug Concentration Peak Onset Therapeutic Range  Duration Sub- Therapeutic Time in Hours

  11. How Do We Study Pharmacology?

  12. Drug Dose Administration Disintegration of Drug Absorption/distribution metabolism/excretion Drug/Receptor Interaction Drug Effect or Response General Concepts Pharmaceutical Pharmacokinetics Pharmacodynamics Pharmacotherapeutics

  13. How are Drugs Administered?

  14. Routes of Drug Delivery Parenteral (IV) Inhaled Oral Transdermal Parenteral (SC, IM) Topical Rectal

  15. What Happens After Drug Administration? Drug at site of administration 1. Absorption Drug in plasma 2. Distribution Drug/metabolites in tissues 3. Metabolism 4. Elimination Drug/metabolites in urine, feces, bile Modified from Mycek et al. (1997)

  16. We are now talking about … Pharmacokinetics

  17. Factors Affecting Drug Absorption • Transport • active vs. passive • pH • Physical factors • blood flow • surface area • contact time ATP ADP + Pi A- BH+

  18. What Factors Affect Distribution? • Blood flow • brain vs. fat • Capillary permeability • differences in capillary structure • Binding to proteins • role of albumin Endothelial cells in liver capillary Endothelial cells in brain capillary Glial cell

  19. An Important Concept:BIOAVAILABIITY • Def’n: • Fraction of a drug that reaches systemic circulation after a particular route of admin’n • Affected by: • 1st pass metabolism (eg: Lidocaine, propranolol) • Solubility • Instability (eg: Penicillin G, insulin) Injected Dose Serum Concentration Oral Dose Time

  20. Volume of Drug Distribution • Drugs may distribute into any or all of the following compartments: • Plasma • Interstitial Fluid • Intracellular Fluid Plasma (4 litres) Interstitial Fluid (10 litres) Intracellular Fluid (28 litres)

  21. So What? • Most drugs distribute into several compartments; however … • Some drugs distribute into only one or two compartments • Eg: Aminoglycoside antibiotics • Streptomycin • Gentamycin Arggh! I can’t fit through these darn fenestrations!

  22. More “So What?” • It takes time for a drug to distribute in the body • Drug distribution is affected by elimination 1.5 Drug is not eliminated 1.0 Serum Concentration Elimination Phase 0.5 Distribution Phase Drug is eliminated 0 Time 0

  23. Albumin Affects Distribution Albumin • Drugs bind differentially to albumin • 2 drug classifications: • Class I: dose less than available binding sites (eg: most drugs) • Class II: dose greater than binding sites (eg: sulfonamide) • The problem: • one drug may out-compete the other Drug X Sulfonamide

  24. Drug Metabolism(we’re still talking about Pharmacokinetics)

  25. Drug Metabolism • First pass • metabolism of drugs may occur as they cross the intestine or transit the liver • eg: nitroglycerin • Other drugs may be destroyed before absorption • eg: penicillin • Such reactions decrease delivery to the target tissues

  26. Drug Metabolism (cont’d) Drug • Two Phases: I and II • Phase I: conversion to lipophilic cpds • Phase II: conjugation • Phase I involves the cytochrome P-450 system • Ultimate effect is to facilitate elimination Phase I Oxidation Reduction Hydrolysis Activation/Inactivation Phase II Glucuronidation Conjugation Products

  27. An Example of Phase I and IIBiotransformation: Phenacetin -OC2H5 CH3CON- H PHASE I Paracetamol -OH CH3CON- H PHASE II OH Glucuronic Acid Conjugate -O- HO -OH CH3CON- H O COOH

  28. An Example of Drug Metabolism

  29. First Pass Metabolism Occurs Primarily in the Liver and Gut

  30. Drug Elimination • Most important route is the kidney • May also involve bile, intestine, lung, breast milk • What clinical scenarios may affect drug elimination?

  31. Elimination of a drug is usually linked to renal filtration, secretion and reabsorption.

  32. Food for Thought • What conditions might affect renal function (and therefore drug elimination)? • What other organ systems are involved in drug clearance?

  33. Important Point • The pharmacokinetic profile of a drug also depends on its mode of administration …

  34. Plasma Concentration Time Example: Intravenous Infusions • Plasma concentration rises until elimination = input • Faster infusions get more drugs on board, but does not change the time to achieve a steady state Fast Infusion Slow Infusion Time at which steady state is achieved

  35. Plasma Concentration Time Example: Intravenous Injection • Peak plasma concentration of the drug is achieved at time = 0 • There is no steady state concentration. Why? 100 mg injected 50 mg injected

  36. Plasma Concentration Time Example: Oral Dose • A single oral dose will give you a single peak plasma concentration • The drug concentration then continuously declines • Repeated doses result in oscillations in plasma concentration

  37. Are We Having Fun Yet?

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