Basic Pharmacology
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Transcript of Basic Pharmacology
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Basic Pharmacology
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What is a drug?- any chemical agent which
effects any biological process
What is pharmacology ?- the study of how drugs effect biological systems
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Introduction A. Physical Nature of Drugs
Solid drugs -> oral routeaspirin or atropine
Liquid drugs -> oral route, IM, SCnicotine or ethanol
Gaseous drugs -> inhalationnitrous 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 Pharmacodynamics What the body does to drug What the drug does to body
Pharmacotherapeutics Pharmacocognosy The study of the use of drugs Identifying crude materials as drugs
Toxicology
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PharmacokineticsWhat the body does to the drug
- 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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PharmacodynamicsWhat the drug does to the body
- Drug receptors- Effects of drug- Responses to drugs- Toxicity and adverse effects of drugs
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Sources of DrugsPharmacocognosy
AnimalsPlants
MineralsSyntheticMicrobes
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Many of these old sources are still in use todayFoxglove plant
Meadow flower Colchicum autumnale
Beef or pork pancreas
Digitalis comes from the foxglove plant and is used in the treatment of CHF
Colchicine is the drug of choice for treatment of gout
Insulin is used today to treat diabetes and is derived from the pancreas of beef or pork or may be synthetically produced as well.
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Drugs Derived from Plants
Ephedrine is present in the leaves of a bushy shrub (species name Ephedra), which, when burned were used by the ancient Chinese to treat respiratory ailments. Today, it is a bronchodilator.
Many estrogen hormone replacement therapy drugs are derived from yams.
The belladonna plant – source of atropine, which is 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. serotonin agonist).
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Drug Nomenclature
- Chemical name - *Generic name - Trade name
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 Administration Critical to efficacy
Rapidity of onsetDuration of effectsMagnitude of effects
Systemic administrationDrug into circulatory system via ...
Enteral routes Parenteral routes
Drug effects throughout body ~
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Routes of Drug Administration
Enteral within or by way of the GI tract
Oral (PO), rectal, sublingual
Parenteral Not within the alimentary canal
Inhalation, IM, SC, IP, topical
Central Into the brain or spinal cord Intrathecal, ICV
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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 = intracerebroventricular =directly into the ventricle of the brain
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Oral Per Os (PO)
by mouthabsorption across
membrane in GImost commonmost variable1st pass metabolism
Cooperation required Can recall ~
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Oral Sublingual
Absorption: mucous membrane salivary glands
e.g., nitroglycerin, buprenorphine
Chewingabsorbed across lining of
mouth ~
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Injection Intravenous (iv)
directly into vein rapid onset of effects
Fastest ~ Intramuscular (im)
Location important Deltoid - rapid Thigh - moderate Buttocks - slowest Difference in blood supply & distance
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Routes of Drug Administration and Absorption.
Injecting (Intravenous): Puts drugs directly
into a vein
Put drugs into muscles or under skin
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Intravenous (IV)Intravenous (IV) 15 15 –– 30 seconds30 secondsIntramuscular (IM) Intramuscular (IM) 3 3 –– 5 minutes5 minutesSubcutaneousSubcutaneous 3 3 –– 5 minutes5 minutes
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Injection
Subcutaneous (sc)under skinslow, steady absorption
DisadvantagesVariable absorption limited volumeskin irritations ~
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Injection
Intrathecal under sheath of nerve fibers,
spinal cord, or brain Mostly as local anesthesia
little importance for most psychoactive drugs ~
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Inhalation
Smoking Lungs
gases or vaporsdensely lined with capillaries large surface area
Fast absorptionSimilar to iv ~
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Routes of Drug Administration and Absorption.
Inhaling: Allows the vaporized
drug to enter the lungs, the heart and then the brain in about 7-10 seconds (Most rapid)
(Pictures) Marijuana inhaling tent used
by the Scythians, c. 500 B.C. Man in India smokes ganja
(marijuana) in a “chillum” pipe.
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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 vaginal
absorption incomplete & unpredictable Pellets - Norplant Microcatheter & pump ~
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Routes of Drug Administration and Absorption
Contact or Transdermal Absorption
Absorption through the skin is the slowest method of drug use. It often takes 1–2 days for effects to begin and the absorption can continue for about 7 days. Nicotine, fentanyl, and heart medications can also be absorbed this way
Skin creams & ointments absorbed through skin
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Contact or Contact or Transdermal: Transdermal: 1 to 2 days1 to 2 days
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Toxicity
Toxicity is the ability of a chemical to damage an organ system, to disrupt a biochemical process, or to disturb an enzyme system.
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Drug Formulation
Dosage = the amount of drug to be administeredusually based on weightExample: mg/kg
Concentration = how the drug is formulatedExample: mg/ml
Injection Volume = a liquid measurement based on weight
Example: ml/kg
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Factors Affecting Response to Drugs
Dosage
Route of Administration IV IH subling IM, SC IP 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
Agonists activates or enhances
cellular activity. triggers a series of
biochemical events alteration in function second messengers:
biochemicals that initiate these changes
Antagonists do not initiate a change
in cellular function. prevent the binding and
the action of agonists “blockers”
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Drug-Receptor Interactions
Factors Governing Drug Action
1. Affinity: measure of the tightness that a drug binds to the receptor
2. Intrinsic activity: measure of the ability 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 complementary surfaces on the receptor.
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Antagonist
exhibit affinity for the receptor do not have intrinsic activity at the receptor competitive antagonist: binds to the receptor
in a reversible mass-action manner -agonists given in high concentrations
can displace the antagonist from the receptor
-agonist can then produce its effect