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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
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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.
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Inhaling: 7 to 10 secondsInhaling: 7 to 10 seconds
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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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http://www.uky.edu/~mtp/decor/mp/antag.swf