PHARMACOKINETICS Flashcards
pharmacokinetics
the study of the movement of drugs within the body
what are the four processes
absorption
distribution
metabolism
excretion
Absorption
the movement of drug particles from the time it enters the body until it is in the bloodstream
Drug Route
how the drug gets into the body
a. enteral
b. parenteral
c. topical
Enteral
relating to the GI tract, from the mouth to the anus
a. buccal
b. sublingual
c. oral
d. stomach-G tube
e. Intestinal J-tube
f. rectal
Parenteral
injectable solutions, emulsions, suspensions
a. intradermal
b. subcutaneous
c. intramuscular
d. intravenous
e. epidural
f. intrathecal
Topical
applied to an epithelial surface
a. skin
b. eyes and ears
c. nose and lungs
d. vagina
Absorption depends on
a. dosage form and drug route
b. GI function
c. blood flow
d. status of absorptive surface
e. temp. food, disease, pain, stress, hunger, fasting, age
a.Bioavailability
the amount of drug that reaches the systemic circulation and the bioavailability =absorption-first pass effect often expressed as a percentage of the administered drug.
DISTRIBUTION
the transport by the circulatory system of a drug to the site of action, which is moving drugs through the body
a. blood flow
heart, liver, kidneys, and brain have good perfusion
liver 25%, kidneys 20%, brain 15%
skin and muscle have less circulation
bone and fat has little circulation
Polarity of the molecule
lipid soluble or water soluble molecules
Protein Binding effect
drug temporarily attach to plasma proteins
a. bound drug- the amount of drug that is attached to the blood proteins can NOT pass through capillary wall
b. free drug the amount of drug that is not attached to blood proteins unattached drug is free to leave the bloodstream and enter cells
Tissue Attraction
a. BBB- blood-brain barrier, which is tightly packed endothelial cells that prevent medication from passing into the brain
METABOLISM
also known as Biotransformation, some drugs are activated by the liver, process where the body changes drugs
parent drug
the drug that is administered and will be metabolized
prodrug- turn into active form
codeine becomes morphine
metabolite
the chemically altered drug
Liver
the primary site of metabolism
a. inactive metabolites
b water-soluble substances
c. more potent metabolites
FIRST-PASS EFFECT
the initial metabolism by the liver which decreases bioavailability of enteral drugs the liver may change some of the drug into an inactive metabolite
EXCRETION
elimination of drug and metabolites from the body
A. route
1. kidneys
a. nephron- the structural unit of the kidney
Creatinine Clearance the amount of creatinine removed by the kidney.
B. Biliary Excretion- liver excretes fat soluble drugs in the bile
C. Also sweat, saliva, breast milk, and lungs
HALF-LIFE
time required for the blood concentration of a drug to decrease by 50% determined by the rate of metabolism and excretion
DRUG EFFECT
cellular processes caused by the drug
a. drug effect curve
Therapeutic effect
the intended effect of a drug
MEC
minimal effective concentration of the drug to attain the therapeutic effect
Onset of Action
time it takes for a drug to reach a therapeutic response
Duration of Action
the length of time that the drug concentration is sufficient to elicit a therapeutic response
Peak Level
the highest blood concentration of the drug
Peak Effect
TIME to reach a drug’s maximum therapeutic response
Toxic Level
the amount of drug that causes more harm than good
Therapeutic Range
the difference between the minimal effective concentration and the toxic level
Narrow Therapeutic Index
a low ratio between the drug benefits to its toxic effects
Wide Therapeutic Index
a relatively large difference between the minimal effective concentration and the toxic level
Steady State
the amount of drug being absorbed is equal to the amount being excreted
Trough Level
the lowest blood concentration of the drug during therapy
Loading Dose
a large amount of drug used to rapidly achieve MEC
a. a rapid injection
