Basic Pharmacology

What is a drug?

any chemical agent which effects any biological process What is pharmacology ?

the study of how drugs effect biological systems

IntroductionA. Physical Nature of DrugsSolid drugs -> oral routeaspirin or atropineLiquid drugs -> oral route, IM, SCnicotine or ethanolGaseous drugs -> inhalationnitrous oxide, halothane, amylnitrite

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

What is Pharmacology ?

Pharmacology

Pharmacokinetics Pharmacodynamics What the body does to drug What the drug does to bodyPharmacotherapeutics Pharmacocognosy The study of the use of drugs Identifying crude materials as drugsToxicology

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 %

PharmacodynamicsWhat the drug does to the body

- Drug receptors- Effects of drug- Responses to drugs- Toxicity and adverse effects of drugs

Sources of Drugs PharmacocognosyAnimalsPlants MineralsSyntheticMicrobes

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.

Drugs Derived from PlantsEphedrine 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.

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).

Drug Nomenclature- Chemical name - *Generic name - Trade nameChemical 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)

Routes of AdministrationCritical to efficacyRapidity of onsetDuration of effectsMagnitude of effectsSystemic administrationDrug into circulatory system via ... Enteral routes Parenteral routesDrug effects throughout body ~

Routes of Drug AdministrationEnteral within or by way of the GI tract Oral (PO), rectal, sublingualParenteralNot within the alimentary canalInhalation, IM, SC, IP, topicalCentralInto the brain or spinal cordIntrathecal, ICV

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

OralPer Os (PO)by mouthabsorption across membrane in GImost commonmost variable1st pass metabolismCooperation requiredCan recall ~

OralSublingualAbsorption: mucous membrane salivary glandse.g., nitroglycerin, buprenorphine Chewingabsorbed across lining of mouth ~

InjectionIntravenous (iv)directly into veinrapid onset of effectsFastest ~ Intramuscular (im)Location importantDeltoid - rapid Thigh - moderateButtocks - slowestDifference in blood supply & distance

Routes of Drug Administration and Absorption.

Injecting (Intravenous): Puts drugs directly into a vein Put drugs into muscles or under skin

InjectionSubcutaneous (sc)under skinslow, steady absorptionDisadvantagesVariable absorptionlimited volumeskin irritations ~

InjectionIntrathecal under sheath of nerve fibers, spinal cord, or brainMostly as local anesthesialittle importance for most psychoactive drugs ~

InhalationSmokingLungsgases or vaporsdensely lined with capillarieslarge surface areaFast absorptionSimilar to iv ~

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.

Other routesTransdermal patchesabsorbed by skinslow continuous releasealso liposomes: via injectionSuppositories - rectal or vaginalabsorption incomplete & unpredictablePellets - NorplantMicrocatheter & pump ~

Routes of Drug Administration and AbsorptionContact or Transdermal Absorption Absorption through the skin is the slowest method of drug use. It often takes 12 days for effects to begin and the absorption can continue for about 7 days. Nicotine, fentanyl, and heart medications can also be absorbed this waySkin creams & ointments absorbed through skin

Toxicity

Toxicity is the ability of a chemical to damage an organ system, to disrupt a biochemical process, or to disturb an enzyme system.

Drug FormulationDosage = 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 weightExample: ml/kg

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

Drug-Receptor InteractionsAgonistsactivates or enhances cellular activity. triggers a series of biochemical events alteration in function second messengers: biochemicals that initiate these changesAntagonists do not initiate a change in cellular function. prevent the binding and the action of agonists blockers

Drug-Receptor InteractionsFactors 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

Binding of a drugdrug must interact with complementary surfaces on the receptor.

Antagonistexhibit affinity for the receptordo 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

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