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Introduction to Pharmacology

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Presentation on theme: "Introduction to Pharmacology"— Presentation transcript:

1 Introduction to Pharmacology
อ. ภญ. ปวิตรา พูลบุตร Pawitra Pulbutr B.Pharm (Hon.), M.Sc in Pharm (Pharmacology)

2 Objectives เข้าใจความหมายของเภสัชวิทยา
อธิบายความหมายของเภสัชจลนศาสตร์และเภสัชพลศาสตร์ เข้าใจถึงการออกฤทธิ์ของยาโดยการจับกับ Receptor, ความหมายของAffinity และ Efficacy เข้าใจความหมายของ Agonist, Partial agonist และ Antagonist พร้อมทั้งแยกความแตกต่างได้ อธิบายการเกิด Antagonism และ Enhancement of drug effectsในรูปแบบต่างๆ เข้าใจ Quantal dose-response curve และ Graded dose response relations

3 What is Pharmacology? Pharmacology can be defined as the study of the manner in which the functions of the living systems is affected by chemical agent

4 Mechanism of drug action
DRUGS Interaction Chemical agents Living System Drug fate in the body Mechanism of drug action Absorption Distribution Metabolism Elimination Pharmacologic effect Physiological Biochemical Desired Treatment Prophylaxis Undesired Side effect Toxicity

5 Medicine What is drug? Chemicals Alters biological functions
Do not create new functions Interact with “specific molecule” (target) in the body Intrinsic substance OR Xenobiotics

6 Drug - Body Interactions
Pharmacodynamics เภสัชพลศาสตร์ What drug does to the body Pharmacokinetics เภสัชจลนศาสตร์ What body does to the drug

7 (Adverse drug reaction; ADRs)
Pharmacodynamics What drug does to the body How do drugs act ?… Mechanism of action Drug-Target Interactions Dose response relationship Mechanism of action Desired effects (Clinical response) Undesired effects (Adverse drug reaction; ADRs)

8 Target for drug action Protein Other eg. DNA RNA, Tubulin Receptors
Ion channels Enzymes Carrier molecules

9 Pharmacokinetics Drug concentration at sites of actions
What body does to the drug Drug fate in the body Absorption Distribution Metabolism Excretion Drug concentration at sites of actions Elimination Drug action Onset & Duration of action

10 Dose of drug administered
absorption Drug concentration In systemic circulation Drug in tissues or distribution distribution Pharmacokinetics distribution Drug concentration at site of action Elimination Drug metabolized or excreted Pharmacologic effect Pharmacodynamics Clinical response Toxicity Efficacy Figure 1.1 Schematic representation of the pharmacokinetic and pharmacodynamic processes that link the administration of drugs to its effects

11 Ligand can either stimulate or block receptor
Drug acts at receptor Ligand can either stimulate or block receptor Stimulate … “Agonist” Block … “Antagonist” Drug or Ligand Receptor

12 KA = drug concentration which have 50% occupancy at equilibrium
KA indicates Affinity; ความชอบจับของยากับ receptors High KA ; Low Affinity MODEL 50 % occupancy Low KA ; High Affinity

13 Theoretical relationship between occupancy and ligand concentration
KA = drug concentration which have 50% occupancy at equilibrium KA indicate affinity


15 Concentration Effect Curve
Concentration effect curve is not equal to occupancy concentration curve Can not indicate the affinity … response is not related to affinity

16 Agonists VS Antagonists Ligand = Agents that bind to receptor
Drugs act at receptor (one type of drug target) Ligand = Agents that bind to receptor Agonists Bind receptor Physiological response Maximal response “ Full agonist” Submaximal response “ Partial agonist”

17 Figure 1.4 Theoretical occupancy and response curve for full and partial agonist
Response full agonist A= Full agonist Occupancy Response Response B= Partial agonist Response partial agonist Occupancy 0.5 1.0 Concentration

18 A & C = Full agonist B & D = Partial agonist

19 Agonist has both “Affinity & Efficacy” Antagonist has only “Affinity”
Bind receptor No physiological response Block receptor Prevent endogenous ligand or agonist binding Agonist has both “Affinity & Efficacy” Antagonist has only “Affinity” Agonist + Antagonist Pharmacologic antagonism

20 Drug antagonism Pharmacologic antagonism Physiologic antagonism Chemical antagonism

21 Agonist + Competitive reversible antagonist

22 Agonist + Irreversible antagonist

23 Enhancement of drug effect
Additive effect 1+1 = 2 Paracetamol + Ibuprofen Synergism 1+1 > 2 Sulfamethoxazole + Trimethoprim Potentiation 0+1 > 1 Penicillin + Probenecid

24 Quantal dose response curve
Quantal response = All or none response Count the number of subjects who response

25 Figure 1.6 Quantal dose effect curves
Median effective dose = ED50 Median lethal dose = LD50 Therapeutic index (T.I.) = LD50 / ED50 More safety… High therapeutic index Figure 1.6 Quantal dose effect curves

26 Graded dose response relations
Different response when increasing the dose Respiratory arrest Drug A Anesthesia Efficacy … A = B Potency… A > B sedation Drug B dose Figure 1.7 Graded dose-response comparison of 2 sedative-hypnotic drugs Efficacy ประสิทธิภาพ …Maximum effect (Emax) Potency ความแรง ...Dose to give the same response (Lower dose; Higher potency)

27 Key words of the day Pharmacology Pharmacokinetics Pharmacodynamics
Affinity … KA Concentration – Occupancy curve Concentration response curve Ligand… Agonist-Antagonist Antagonism Enhancement Quantal dose response relationship Therapeutic index/ Standard margin of safety Efficacy VS Potency

28 Don't be Panic! Q&A

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