5 Pillars of Pharmacology
Drug, Pharmacokinetics, Pharmacodynamics, Pharmacotherapeutics and Drug Toxicity
Pharmacokinetics
Absorption, distribution, metabolism and excretion.
Pharmacodynamics
Mechanism of Action
Pharmacotherapeutics
Therapeutic use of the drug.
Drug Sources
Natural, Synthetic, and Semi-Synthetic
Natural Drug Sources
Plant, Animal, Fungi and Bacteria
Active Compounds in Plants
Alkaloids, Glycosides, Resins, Gums, Tannins, Fixed and Volatile Oils.
Alkaloids
Basic nitrogenous substances that are insoluble in water. End in -ine.
Glycosides
Sugars that are combined with other organic structures.
Resins
Substances formed by the polymerization of volatile oils.
Gums
Polysaccharides from trees.
Tannins
Non-nitrogenous plant parts that produce an astringent effect.
Fixed Oils
Stable oils that will NOT evaporate in air.
Volatile Oils
WILL evaporate when exposed to air.
Animal Sources of Drugs
Blood, plasma, and hormones.
Drugs from Bacteria
Antibiotics
Drugs from Fungi
Antibiotics like penicillin.
Semisynthetic Drug Sources
Chemically treated natural sources.
Synthetic Drug Sources
Highly purified substances.
Solid Drugs
Powder, tablet, pill, bolus, pessary and suppository.
Liquid Drugs
Mixture, tincture, spirit, suspension, elixir, emulsion, extract, infusion, decoction, injection, and lotion.
Semisolid Drugs
Ointment, cream, paste, electuary.
Gases / Vapor Drugs
Aerosol, spray and mist.
Routes of Administration
Local, Systemic and Parenteral.
Local Routes
TOPICAL TREATMENTS: Skin, nasal, ocular, urinary tract, vaginal, rectal, mammary, lingual/sublingual, GI tract lining, otic, epidural, intraspinal, intrasynovial, and intramedullary.
Systemic Routes
ENTERAL - per os. (By mouth / feeding tube) PARENTERAL - extra-oral / GI route.
Parenteral
Injection & Inhalation
Enteral Route Advantages
Generally safe, convenient, feeding tubes for non-compliant patient, and infection at site not a concern.
Enteral Route Disadvantages
Slower onset of action, inactivation by enzymes, food/drugs may affect absorption, GI activity/integrity, GI upset, and patient/owner compliance.
IV Advantages
Rapid onset, less irritating than injecting into tissue, and larger volumes can be given.
IV Disadvantages
Risk of complications, and some drugs can irritate veins.
IM Advantages
Rapidly absorbed, longer duration of action, and suspensions can be given.
IM Disadvantages
Risk of tissue damage, and risk of admin site infection.
SubQ Advantages
Constant absorption, longer duration of action, and can give at home.
SubQ Disadvantages
Slow onset, cannot use irritating drugs, and risk of admin site infection.
Therapeutic Factors Affecting Route Selection
Onset of action, duration of action, site of action, and adverse reactions.
Drug Factors Affecting Route Selection
Irritating properties, solubility, and pH.
Powder
Mixture of drugs packaged in packets / sachets.
Tablet
Active drug combined with a binder and excipient and compressed by machine. Marked for splitting.
Enteric-Coated Tablets
Drugs that are insoluble in acid but will dissolve in the alkaline small intestine.
Pill
Mixture of drugs and sticky binder and coated with sugar coating. NOT marked for splitting.
Capsule
Suitable for both powder and liquid drugs. Mixture of gelatin and glycerin.
Bolus
Used for horses and cattle.
Mixture
Aqueous solution or suspension intended for oral administration.
Pessary
Conical solid preparation given intrarvaginally for systemic effect in humans.
Paste
Semisolid preparation for external / internal use.
Electuary
Semisolid applied to the back of the tongue. Used in large animal medicine.
Tincture
NONVOLATILE: alcoholic liquid preparation of a nonvolatile substance for internal/external use.
Spirit
Volatile alcoholic liquid preparation.
Suspension
Aqueous suspension of solids with a dispersing agent.
Syrup
Solution of medical agents, flavoring and coloring agents in 85% sucrose solution.
Elixir
HYDROALCOHOLIC solution of medicinal agents that have been sweetened and flavored.
Emulsion
Oily substance dispersed in an aqueous medium with an emulsifying/dispersing agent.
Extract
Infusion & Decoction: obtained by passing the solvent over the dried plant material, then evaporating the solvent.
Infusion
Extract prepared with cold water.
Decoction
Extract prepared with boiling water.
Liniment
Rubbed on to increase blood supply to the area.
Lotion
Must be liquid, for soothing and relieving pain.
Ointment
Semisolid and greasy.
Cream
Leaves a film of oil on the skin once water has evaporated.
Therapeutic Index
LD50/ED50
LD50
Amount of drug given that caused death in 50% of tested animals.
ED50
Effective dose in 50% of animals tested.
Standard Safety Margin
[(LD1-ED99)/ED99] x 100
Dose
Amount of drug given to achieve a certain effect.
Dosage
Amount of drug per unit of body weight.
Concentration
Amount of drug per unit of volume from the stock supply of medication.
Prescription Drugs
Regulated by the FDA
Biologics / Vaccines
Regulated by the USDA
Controlled Substances / Drugs
Regulated by the DEA
(NDC) National Drug Code
Required on ALL Rx medications and is assigned by the DEA.
(NADA) Number - New Animal Drug Application
Assigned by the FDA following drug approval.
Class I / Schedule I Drugs
Have the highest abuse potential with no accepted medical use.
Class II / Schedule II Drugs
Must be a written Rx with NO refills.
Class III / Schedule III Drugs
Accepted medical use, with moderate abuse potential.
Class IV / Schedule IV Drugs
Accepted medical use with lower abuse potential.
Class V / Schedule V Drugs
Lowest abuse potential
Rx
Order to a pharmacist by a licensed medical practitioner.
Components of a Rx
Superscription, Inscription, Subscription, Transcription, Practitioner Signature.
AMDUCA
Allows veterinarians to prescribe extra-label use.
Required Information for Rx
Hospital Information. Patient: name, species, weight. Client: name and address. Date Rx was written, # of refills, Clinician’s DEA reg # for controlled drugs, and withdrawal time for food animals.
Drug Information for Rx
Name and strength of medication, quantity dispensed, and directions for use.
Rx for Schedule II Drugs
Must be written Rx, NO refills, can only be a 30 day supply.
Rx for Schedule III, IV and V
Up to 5 refills within 6 months from when Rx is written.
(FARAD) Food Animal Residues Avoidance Databank
Withdrawal times for food animals.
Compounded Medications
Drug created by combining or altering ingredients. Done by a licensed vet or pharmacist.
Posology
Study of drug doses.
Toxic Dose
Produces adverse clinical, hematological, or biochemical changes.
Volume from Stock Solution
% required dilution x total volume needed / % stock solution.
Factors Modifying Dose and Drug Response
Animal, drug, and the environment.
Animal Factors Modifying Dose and Drug Response
Species, breed, individual. Body weight, age, sex, temperament. Idiosyncrasy, hypersensitivity, disease, and tolerance.
Drug Factors Modifying Dose and Drug Response
Route & timing of administration, cumulation, and drug-drug interaction.
Environment Factors Modifying Dose and Drug Response
Ambient temperature, humidity, and oxygen.
Species Factors Modifying Dose and Drug Response
Anatomic, physiologic, and biochemical.
Breed Factors Modifying Dose and Drug Response
Herding breeds sensitive to many drugs, and brachycephalics sensitive to phenothiazines.
Individual Factors Modifying Dose and Drug Response
Genetic differences, learn from individuals drug response, and educate the client and care staff.
Newborn to Pediatric Effects
Decreased: metabolism, excretion, plasma protein binding, blood brain barrier (BBB). Increase total body water.
Geriatric Effects
Decreased: metabolic enzymes, hepatic blood flow, renal function, cardiac output, total body water, plasma protein, lean body mass. Increase: body fat, distribution.
Idiosyncrasy
Individual drug sensitivity NOT dose-dependent.
Hypersensitivity
Allergic drug reaction.
Hepatic Dysfunction
Cannot metabolize normally; decreased metabolism.
Renal Insufficiency
Cannot excrete in urine normally; decreased excretion.
Congestive Heart Failure
Cannot pump drug to site of excretion normally; decreased renal excretion.
Tolerance
Unusual resistance to ordinary drug dose. Natural, acquired, cross-tolerance, and tachyphylaxis.
Cumulation
Leads to accumulation; occurs when the rate of elimination is slower than the rate of absorption.
Drug-Drug Interactions
Summation, potentiation, synergism, and antagonism.
Summation
Sub of the effects of the drugs.
Potentiation
Intensification of effects, give another drug with DIFFERENT action.
Synergism
Exaggeration of effects, give another drug with the SAME action.
Antagonism
Decreased effect of another drug. Chemical, physical (histamine) and pharmacological (competitive, non-competitive, and uncompetitive).
Metabolism
Liver
Excretion
Kidney
Pharmacodynamic Drug Interactions
Two drugs act on the same receptors.
Pharmacokinetic Drug Interactions
Alteration of: absorption, distribution, biotransformation, and excretion.