vptox pharmocokinetics

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vptox pharmacokinetics

pharmacokinetic parameters

steady state plasma conc Repeated dosing of a drug at regular intervals,

HALF-LIFE, t1/2 Time required for concentration of drug to be reduced by half.

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CLEARANCE, Cl  A measure of the capacity of the body to remove a drug.

VOLUME OF DISTRIBUTION, Vd  Hypothetical volume of body fluid into which the absorbed drug is disseminated

bioavailability Fraction of chemically unchanged drug (%) that reaches the systemic circulation by any route

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drug excretion Process by which a drug or metabolite is removed from the body

fecal lung milk

renal most common

3 processes filtration secretion reabsoption

filtration - glomerular filtration rate secretion - takes place in proximal convoluted tube reabsorption - takes place in distal convoluted tube

Urine pH • Urine flow rate • Plasma protein binding • Competition for active tubular secretion • State of renal function

drug biotransformation(metabolism) -Chemical modification of compound by an organism

enterohepatic cycling -drug excreted through bile -reabsorbed in small intestine -recycled to liver through hepatic portal vein

first pass effect -have to pass through liver before reaching circulation

factors affecting

genetic diseases liver diseases

phase 1

phase 2

Endogenous substrates Animo acid Glucuronic acid Sulfuric acid Acetic acid

Drugs NOT eliminated in phase I undergo phase II make drugs water-soluble for elimination through kidneys.

Cytochrome P-450 being the major enzymes

chemical reactions -oxidation -reduction - hydrolysis

Convert parent drug to a more polar metabolite by introducing/unmasking polar functional group

purposes • Inactivate drug • Converting to water-soluble form for elimination by the kidneys

drug distribution -Process of drug leaving circulation and entering extracellular space/cells of tissues

cells/tissues

extracellular space

interstitium cells

movement depends on -drug properties -blood flow -capillary permeability

plasma -free drug=active -bound drug=inactive

plasma drug concentration -predict efficacy/side effects

factors affecting plasma drug conc -dosage form -drug-drug interaction

drug absorption - Transfer of a drug from its site of administration into bloodstream

mechanisms of drug absorption -passive diffusion -active transport -endocytosis -exocytosis

factors affecting absorption

disease status of patients -GI disease -cardiac disease=less blood flow=less absorption

drug-drug interaction -can increase or inhibit absorption

dosage forms -affect dissolution therefore absorption

surface area for absorption -bigger surface area=greater absorption

blood flow to site -more blood flow = greater absorption

drug properties -size -hydrophilicity -hydrophobicity

routes of administration -iv -im -oral

oral route absorption -stomach -small intestine

drug dosage forms -physical form of drug intended for administration via various routes.

rectal -enemas -enemas

transdermal -patches -plasters

topical -cream -gel

intranasal -spray

inhalation -aerosol

injectables

solution oil (by IV or direct injection)

sublingual

tablets chewing gums

oral

liquid -emulsions -solutions

solid -capsules -powders

routes of drug administration

others

transdermal -drug absorbed into skin

rectal -administered through the rectum

topical -directly into affected areas

intranasal -directly into nose

inhalational -deep breathing of drug into respiratory tract

parental (injection) -avoids first pass effect in liver -contamination

IV -inject directly into vein

IM -injected into muslce

ID -injected into skin

SC -injected into fatty layer of tissue below skin

IP -injectected into intraperitoneal cavity

EPIDURAL -injected into space outside dura matter

intrathecal and intracerebroventricular -injected into csf cerebrospinal fluid

enteral(mouth)

sublingual -drug absorbed by normal mucosa -avoid first pass effect of liver -can only administer small quantity of drug

oral -most common route -easy to administer -slow onset of action

actions of body on drug

• Study of the movement/transformation of drug substances through body compartments

-Refers to the processes of Absorption, Distribution, Metabolism, Elimination --determines the concentration of drugs in body tissues and fluids over time