Drug Action: Parmaceutic, Pharmcokinetic and Pharmacodynamic Phases Flashcards

Terms Definitions
pharmaceutic phase
the first phase of drug action, also known as dissolution
disintegration
the breakdown of a tablet into smaller particles
dissolution
the dissolving of smaller particles into the GI fluid before absorption
Rate limiting
the time it takes the drug to disintegrate and dissolve to become avaliable to the body to absorb it
pharmacokinetic phase
the process of drug movement to achieve drug action. The 4 processes are absorption, distribution, metabolism (or biotransformation) and excretion (or elimination).
absorption
the movement of drug particles from the GI tract to body fluids by passive absorption, active absorption or pinocytosis
passive absorption
occurs mostly by diffusion (movement from higher concentration to lower concentration); energy is not required
active absorption
requires a carrier such as an enzyme or protein to move the drug against a concentration gradient; energy is required
pinocytosis
is a process by which cells carry a drug accros their memebrane by engulfing the drug particles
*Remember*
drugs that are lipid soluble and nonionized are absorbed faster than water-soluble ad ionized drugs
first-pass effect
the process in which the drug passes to the liver first, ex: wafrarin and morphine
Bioavailibility
a subcategory of absorption; it is the % of the administered drug dose that reaches the systemic circulation.
Factors that affect Bioavailibility
Bioavailibility the drug form, the route, GI mucosa and motility, food and other drugs and changes in liver metabolism
distribution
the process by which the drug becomes avaliable to the body fluids and body tissues
half-life
the time it takes for one half of the drug concentration to be eliminated
elimination
main route is through the kidneys
creatinine clearance
most accurate test to determine renal function
pharmacodynamic
is the study of drug concentration and its effects on the body
onset of action
the time it takes to reach the minimum effective concentration (MEC) after a drug is administered
peak action
occurs when the druge reaches its highest blood or plasma concentration
duration of action
is the length of time the drug as a pharmacologic effect
time-response curve
evaluates 3 parameters of drug action; the onset of drug action, peak action and duration of action
receptor families
4 families; kinase-linked receptor, ligand-gated ion channels, G protein-coupled receptor systems and nuclear receptors
ligand-binding domain
the site on the receptor in which drugs bind
kinase-linked receptors
the ligand-binding domain for drug binding is on the cell surface, the drug activates the enzyme (inside the cell) and a response is initiated
ligand-gated ion channels
the drug spans the cell memebrane and with this type of repetor,the channel opens, allowing for the flow of ions into and out of the cell. The ions are primarily sodium and calcium
G protein-coupled receptor systems
there are 3 components to this receptor response; the receptor, G protein that binds with guanosine triphosphate and the effector that is either an enzyme or an ion channel
nuclear receptors
cell nucleus and not on the surface of the cell membrane, activation of receptors through the transcription factor is prolonged
agonists
drugs that produce a response
antagonists
drugs that block a response
nonspecific drugs
drugs that affect various sites, have properties of nonspecificity
nonselective drugs
drugs that affect various receptors; have properties of nonselectivity
Categories of drug action
stimulation or depression, replacement, inhibition or killing of organisms, irritation
theraputic index
estimates the margin of safety of a drug through the use of a ratio that measres the effective dose (ED) in 50% of persons/animals and the lethal dose (LD) in 50% of people/animals; the close the ratio is to 1, the greater danger of toxicity
low theraputic index
drugs that have a narrow margin of safety; small safety range between the ED and LD
high theraputic index
drugs that have a wide margin of safety and less danger of producing toxic effects
theraputic range (window)
the drug concentration that is between the minimum effective concentration in the plasma for obtaining desired drug action and the minimum toxic concentration
peak drug level
the highest plasma concentration of drug at a specific time; indicates rate of absorption
trough drug level
the lowest plasma concentration of a drug and it measures the rate at whichthe drug has been eliminated
loading dose
a large initial dose of drug to achieve a rapid minimum effective concentration in the plasma
side effects
physiologic effects not related to desired drug effects
pharmacogenetics
the effect of a drug action that varies from a predicted drug response because of genetic factors or hereditary influence
tolerance
refers to a decreased responsiveness over the course of therapy
tachyphylaxis
refers to a rapid decrease in response to the drug; think "acute tolerance"
placebo effect
a psychologic benefit from a compound that may not hav the chemincal structure of a drug effect
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