2. basic pharmacology

8/13/2019 2. Basic Pharmacology

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Basic Pharmacology


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What is a drug?- any chemical agent whicheffects any biological process

Drugs these are chemical substances used or intended to be used to modify or explore the physiologicalcondition or pathological state for the benefit of the recipient. Drugs may be used for prevention, diagnosisand treatment.

Prevention BCG vaccine, Anti-malarial drugs for malarial prophylaxis. Diagnosis Barium meal for Peptic ulcer diagnosis. Treatment Anti-biotic, Anti-TB drugs.

What is pharmacology ?

- the study of how drugs

effect biological systems


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Introduction

A. Physical Nature of Drugs Solid drugs -> oral route

aspirin or atropine Liquid drugs -> oral route, IM, SCnicotine or ethanol

Gaseous drugs -> inhalation

nitrous oxide, halothane, amylnitrite

Many drugs are weak acids or basespH differences in the body may alter the degree of

ionization of drug


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What is Pharmacology ?

Pharmacology

Pharmacokinetics PharmacodynamicsWhat the body does to drug What the drug does to body

Pharmacotherapeutics PharmacocognosyThe study of the use of drugs Identifying crude materials as drugs

Toxicology


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Pharmacokinetics

What the bo dy do es to thed rug

- Absorption - Distribution - Metabolism (Biotransformation) - Excretion

Half-life (t1/2) - the time required for the plasmaconcentration of a drug to be reduced by 50


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Pharmacodynamics What the d ru g d oes to the bod y

- Drug receptors

- Effects of drug - Responses to drugs - Toxicity and adverse effects ofdrugs


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Sources of DrugsPh a rm a c o c o g n o sy

Animals

PlantsMineralsSyntheticMicrobes


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Many of these old sources are

still in use todayFoxglove plant

Meadow flowerColchicum autumnale

Beef or pork pancreas

Digitalis comes from thefoxglove plant and is usedin the treatment of CHF

Colchicine is the drug ofchoice for treatment ofgout

Insulin is used today totreat diabetes and isderived from the pancreasof beef or pork or may besynthetically produced aswell.


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Drugs Derived from Plants

Ephedrine is present in the leaves of a bushyshrub (species name Ephedra), which, when

burned were used by the ancient Chinese to treatrespiratory ailments. Today, it is abronchodilator.Many estrogen hormone replacement therapydrugs are derived from yams.The belladonna plant source of atropine, whichis still used to dilate the pupils.


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DRUG CLASSIFICATION

- Based on the chemical structure

- Based on the main effect (e.g. analgesics).

- Based on the therapeutic use (e.g.antipsychotic).

-Based on mechanism of action (e.g. serotoninagonist).


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Drug Nomenclature

Chemical name - *Generic name - Trade nam

Chemical Name: 2-(4-isobutylphenyl)-propionic acid

Generic Name: ibuprofen

Trade Names: Advil, Aches-N-Pain,Brufen,

Emodin, Haltran, Medipren, Midol 200, Motrin, Nuprin, Rufen, Trendar, Wal-Profen

*preclinical nomenclature = company abbrev-123456 (e.g. WAY-100635, MK-869)


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Routes of AdministrationCritical to efficacy

Rapidity of onsetDuration of effects

Magnitude of effectsSystemic administrationDrug into circulatory system via ...

Enteral routes Parenteral routes

Drug effects throughout body ~


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Routes of Drug Administrationcommon abbreviations

PO = per os = oral

IV = intravenous = into the vein

IM = intramuscular = into the muscle

SC = subcutaneous = between the skin and muscle

IP = intraperitoneal = within the peritoneal cavity

icv = intr acerebroventr icul ar =dir ectly into the ventr icle of the brain


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Oral

Per Os (PO)by mouth

absorption acrossmembrane in GImost commonmost variable1 st pass metabolism

Cooperation requiredCan recall ~


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OralSublingual

Absorption: mucous membrane

salivary glandse.g., nitroglycerin,buprenorphine

Chewingabsorbed across lining ofmouth ~


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InjectionIntravenous (iv)

directly into veinrapid onset of effects

Fastest ~ Intramuscular (im)

Location importantDeltoid - rapidThigh - moderateButtocks - slowestDifference in blood supply & distance


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Routes of Drug Administration and Absorption.

Injecting(Intravenous):

Puts drugs directly

into a veinPut drugs intomuscles or underskin

Copyright, 2004, CNS Productions,Inc.

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Intravenous (IV)Intravenous (IV) 1515 30 seconds30 secondsIntramuscular (IM)Intramuscular (IM) 33 5 minutes5 minutesSubcutaneousSubcutaneous 33 5 minutes5 minutes


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Injection

Subcutaneous (sc)under skin

slow, steady absorptionDisadvantages

Variable absorption

limited volumeskin irritations ~


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Injection

Intrathecalunder sheath of nerve fibers, spinal

cord, or brainMostly as local anesthesia

little importance for most psychoactive drugs

~


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Routes of Drug Administration and Absorption.

Inhaling: Allows the vaporizeddrug to enter thelungs, the heart andthen the brain in about7-10 seconds (Mostrapid)

(Pictures)Marijuana inhaling tent usedby the Scythians, c. 500 B.C.Man in India smokes ganja(marijuana) in a chillumpipe.


3

Inhaling: 7 to 10 secondsInhaling: 7 to 10 seconds


1


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Other routes

Transdermal patchesabsorbed by skinslow continuous release

also liposomes: via injection

Suppositories - rectal or vaginalabsorption incomplete & unpredictable

Pellets - NorplantMicrocatheter & pump ~


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Routes of Drug Administration and

AbsorptionContact or Transdermal Absorption Absorption through the

skin is the slowestmethod of drug use. It

often takes 1 2 daysfor effects to begin andthe absorption cancontinue for about 7days. Nicotine,fentanyl, and heartmedications can alsobe absorbed this way

Skin creams & ointmentsabsorbed through skin


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Contact orContact orTransdermal:Transdermal:1 to 2 days1 to 2 days


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Drug Formulation

Dosage = the amount of drug to be administeredusually based on weight

Example: mg/kg

Concentration = how the drug is formulated Example: mg/ml

Injection Volume = a liquid measurement based on weight

Example: ml/kg


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Factors Affecting Response to Drugs

DosageRoute of Administration

I V I H subli ng I M , SC I P PO topical

Rate of Absorption

Rate of Elimination

Physiochemical properties of the drug

age, sex, species, metabolism, etc


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Drug-Receptor Interactions

Agonistsactivates or enhancescellular activity.triggers a series ofbiochemical eventsalteration in function

second messengers:biochemicals thatinitiate these changes

Antagonistsdo not initiate a changein cellular function.

prevent the binding andthe action of agonistsblockers


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Drug-Receptor Interactions

Factors Governing Drug Action

1. Affinity: measure of the tightnessthat a drug binds to the receptor

2. Intrinsic activity: measure of theability of a drug to generate an effect,producing a change in cellular activity


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Binding of a drug

drug must interact with complementarysurfaces on the receptor.


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Antagonist

exhibit affinity for the receptordo not have intrinsic activity at the receptor

competitive antagonist: binds to the receptorin a reversible mass-action manner

-agonists given in high concentrations candisplace the antagonist from the receptor

-agonist can then produce its effect


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2. basic pharmacology

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