Chapter 4 Flashcards
bioavailability
percent of drug administered that enters the systemic circulation
pinocytosis/phagocytosis
type of cellular movement that allows intake of large molecules
volume of distribution
indicator of how well a drug is distributed throughout the body
what type of molecule can perform passive diffusion
lipophilic, nonionized, small
primary site of drug metabolism
liver
drug distribution
physiological movement of drugs from the systemic circulation to the tissues
induce
describes an increase in the rate of metabolism by an enzyme system
ionized
charged
passive diffusion movement
high concentration to low concentration
active transport movement
low concentration to high concentration
what types of drugs absorb well in the GI tract?
hydrophilic drugs
which body compartment gets adequate drug levels the fastest?
fat
what condition will allow for greater volume of distribution?
normal conditions
dehydrated animals will have less
drug affinity
measure of a drug’s strength at which it binds to its receptor
bioequivalency
when two drugs would be expected to be essentially the same
first-pass metabolism
phenomenon of drug metabolism in which the concentration of active drug is greatly reduced before it reaches systemic circulation because it passes through liver first
acidic drug in an acidic environment
nonionized molecules
acidic drug in alkaline environment
ionized molecules
alkaline drug in acidic environment
ionized molecules
alkaline drug in alkaline environment
nonionized molecules
ion trapping
occurs when a drug molecules changes from ionized to nonionized form as it moves from one body compartment to another
tissue perfusion
relative amount of blood supply to an area or body system
free drug
drug that isn’t bound to a protein and is free in blood
penetrates tissues
increased protein binding
less free drug
decreased protein binding
more free drug
more free drug causes more chance for ______
toxicity
biotransformation
(drug metabolism)
chemical alteration of drug molecules into metabolites by body cells
characteristics of metabolites
more hydrophilic, eliminated in urine or bile, wider distribution to tissues or excretion
reactions that cause drugs to be altered by metabolism
- oxidation reactions (lose electrons)
- reduction reactions (gain electrons)
- hydrolysis (adding H2O causing split)
- conjugation (addition of substance which makes drug more water soluble)
other sites that can absorb drugs
kidneys, small intestine, brain/neurologic tissue, lungs, skin
altered absorption
one drug alters absorption of other drugs (antacids)
altered metabolism
same enzyme needed to metabolize more than one drug, slows down metabolizing of both drugs
altered elimination
some drugs act directly on kidney and decrease elimination of other drugs (diuretics)
microsomal enzyme inducers
drugs that induce enzyme system alter metabolism by causing liver to become more efficient
drug tolerance
increased metabolism due to enzyme induction
metabolic: drug is metabolized more rapidly with chronic use
cellular: decreased cellular receptors with repeated use
pathways for elimination
kidneys, liver, intestine, lungs, milk
half life
time required for the concentration of drug in the blood to be reduced by half
steady-state concentration
drug concentration reaches a plateau where peak concentrations and lowest concentrations are the same after repeated doses of drug
minimal effective concentration (MEC)
onset of action begins when drug achieves MEC
peak plasma level
elimination rate of drug is equivalent to rate of absorption
time to peak
time of administration to the time that the peak plasma level is reached
minimum toxic concentration (MTC)
plasma level at which toxic effects are observed
loading dose
given to rapidly achieve therapeutic plasma levels
dissociation constant K
measure of a drug’s affinity for its receptor
