Ch4 - Pharmacokinetics

Physiological movement of drugs in the body

Pharmakokinetics

Four steps of Pharmacokinetics (ADME)

absorption, Distribution, Metabolism, Excretion

Pharmacokinetics includes the movement of substances across the

cell membranes

4 basic mechanisms by which drugs move into cells

passive diffusion, facilitated diffusion, active transport, phagocytosis

3 drug factors affecting absorption

solubility, pH, molecular size

6 patient factors affecting absorption

age, health, metabolic rate, genetic factors, sex, species

Percent of drug administered that enters (makes it into) systemic circulation (bloodstream)

Bioavailability

Drugs given what route has 100% bioavailability

IV

Drugs expected to be the same are ?

bioequivalent

Per FDA - a generic drug must vary less than ? comparison product

20%

Drugs absorbed through GI tract go through the portal venous system to the liver before entering the blood stream

First pass effect

3 examples of drugs effected/inactivated by the First Pass Effect

lidocaine, naloxone, nitroglycerin

Nonparenteral or Parenteral - slower absorption, longer duration of action

Nonparenteral

5 factors effecting absorption rate in gut/GI tract

pH of drug, Solubility, size/shape of molecule, food, GI motility

Administration route with the fastest onset and shortest duration of action

IV

When an injectable drug is put in substance that will delay/slow its absorption

Depot

Depot preparations of drugs are usually given via what route

IM

physiological movement of drugs from systemic circulation to tissues

distribution

4 factors affecting drug distribution

membrane permeability, tissue perfusion, protein binding, volume of distribution

The capillaries in the CNS (brain, spinal cord) do not have

fenestrations

Only most ? drugs can enter the CNS

lipophilic

the relative amount of blood supply to area or body system

Tissue perfusion

Body areas with the highest level of perfusion

vital organs

Body areas with mid-level perfusion

skeletal muscle, bone

Body areas with the lowest perfusion

adipose tissue, connective tissue

Drugs may bind to ? in the blood stopping the bound drug from leaving capillaries due to size

proteins

#1 protein in the blood

Albumin

Albumin is produced by the

liver

Liver disease = ? albumin

less

If an animal has liver disease (less albumin) do they need a higher or lower dose of drug

lower

Do young animals or adult animals have a higher % of body water

young animals

Young animals have a/an ? volume of distribution

increased

Young animals may need higher/lower dose of drug to reach therapeutic levels in target areas

higher

In obese animals dosing should be based on their

lean body weight

Main concern with medicating obese animals

toxicity

Another term for metabolism

biotransformation

The name of the compound created by the chemical alteration of a drug by body of the patient

Metabolite

4 pathways of metabolism

oxidation reactions, reduction reactions, hydrolysis, conjugation

Primary site of drug metabolism

liver

Drugs are metabolized in the liver by what enzyme

cytochrome P450

7 factors affecting biotransformation

species, age, nutritional status, tissue storage, health, liver function, body temp

Increased temp = ? drug metabolism

increased

5 routes of drug elimination

kidney, liver, intestine, sweat, saliva, milk

Kindys eliminate drugs out via

urine

Liver eliminates drugs out via

feces

When drug accumulation and elimination are balanced

steady state

Steady state is typically reached after how many half lives have passed

4-5

3 factors affecting drug elimination

hydration status, age, health

Located of cell surface, in cytoplasm, or within nucleus of cells; 3D proteins

receptors

measure of strength of binding between drug and receptor

Affinity

drug that binds to receptor and causes an action

Agonist

Binds to receptor but causes little action at receptor site

partial agonist

drug that blocks another drug from binding to receptor and blocks action at receptor

antagonist

What is the best route of administration of a drug for a patient in shock (blood is being sent to most vital organs)

IV