Exam 2 Flashcards
What is referred to as drug action
pharmacokinetics
first pass metabolism
- before the blood goes to the rest of the body from the gastrointestinal tract, it passes through the liver
- the liver is the major organ that breaks down drugs. therefore, a certain amount of the drug will be inactivated or metabolized as it goes through the liver.
- other routes may not be subject to this “first pass” effect
- the breakdown of drugs as they are transported through the liver before they reach the rest of the body through the circulatory system
therapeutic effects due to depot binding
slower onset and reduced effects
varying effects
high binding means less free drug so some people seem to need higher doses
low binding means more free drug so they seem more sensitive
higher than expected blood levels of the displaced drug possibly causing greater side effects
drug remains in the body for prolonged action
rapid termination of drug action
side effects
drug-induced effect that accompanies the primary effect for which the drug is administered.
bioavailability
the portion of original drug dose that reaches its site of action.
biotransformation
- drug metabolism
depot binding
- drug binding to inactive sites where no biological effect is initiated (plasma proteins, muscles, fat, bone)
- drug molecules cannot reach active sites or be metabolized by the liver, but binding is reversible
- affects magnitude and duration of drug action
- reduces the concentration of drug at its site of action and delays effects
- individuals vary in the amount of depot binding.
depot binding and its affects on drug action
affects the magnitude and duration of drug action
routes of drug administration
- oral
- intravenous
- intramuscular
- subcutaneous
- topical
- transdermal
- epidural
drug metabolism
bioinformatics
CYP450 families
- CYP1, 2, and 3 = most common for drug metabolism .
- CYP2D6 and CYP3A (especially 3A4) metabolize over 50% of drugs.
first-order elimination
- elimination of a constant fraction of drug, per time unit, of the amount present in the organism. the elimination is proportional to the drug concentration.
half-life
- time it takes for a half of the amount of drug in the circulation to be eliminated
•Mostly in hours; some measured in days.
•First-order elimination.
how many half-lives it usually takes for drugs to be elevated from the system
the ability of a drug to produce its intended effect.
enzyme induction
increased production of drug-metabolizing enzymes in the liver, stimulated but certain drugs (inducers). as a result of induction, drugs that are metabolized by the induced enzyme will degraded more rapidly. it is one mechanism by which pharmacological tolerance is produced.
enzyme inhibition
- some drugs inhibit CYP enzymes and increase their own levels, as well as levels of any drug metabolized by that enzyme.
- can produce much more intense/prolonged drug effects and high levels of drug toxicity
pharmacokinetics
- study of drug molecules into through and out of the body
- science that studies routes of administration absorption and distribution bioavailability biotransformation and excretion of drugs
pharmacodynamics
study of interactions of a drug with the structure with which it interacts to produce its effects
ligands
- neurotransmitters
- can be specific to certain receptors but a drug may be more specific than the endogenous neurotransmitter
- bind to receptors
- any molecule that binds to a receptor with some selectivity.
receptors
- fairly large molecules (usually protein)
- located in sites where naturally occurring compounds (transmitters or modulators) produce biological effect
- neurotransmitters (ligand) can be specific to certain receptors, but a drug may be more specific than the endogenous neurotransmitter.
- drugs form reversible ionic bonds with specific receptors. they do not create unique effects: merely modulate normal neural functioning.
antagonist
- by itself produces no response
- It is possible to determine if a drug has an antagonistic action by seeing if it reduces the effect of the agonist.
- Irreversible or noncompetitive antagonists cause a downward
shift of the maximum, with no shift of the curve on the dose axis. - drugs that attach to receptors and blocks the action of either an endogenous transmitter or an agonistic drug
agonist
drug that attaches to a receptor and produces actions that mimic or potentiate those of endogenous transmitter.
drug potency
measure of drug activity expressed in terms of the amount required to produce an effect of given intensity. potency varies inversely with the amount of drug required to produce this effect- the more potent the drug, the lower the amount required to produce the effect.
drug efficacy
maximum effect obtainable, with additional doses producing no effect. Some drugs may be
potent but might never be able to produce a peak response no matter how much is given.
drug competition
•Some drugs compete for the same metabolic system: elevated level on drug 1 will
reduce metabolic rate of drug 2.
•This is the case for alcohol and sedatives like barbiturates or Valium
what information can we derived from dose-response relationships
•Used to evaluate receptor activity.
•Describes the amount of response for a given drug dose
A. Curve obtained by plotting the dose of drug against the percentage of subjects showing a given
response at any given dose.
B. Curve obtained by plotting the dose of drug against the intensity of response observed in any single
person at a given dose.
sensitization
the opposite of tolerance. sometimes call reversed tolerance. the enhancement of drug effects following repeated administration of same drug dose.
drug tolerance
- state of progressively decreasing responsiveness to a drug.
- a diminished response to the same dose of drug. a larger dose is eventually needed to have the same response as before.
metabolic
More water soluble and less active (or inactive) than parent drug.
steady state
the point of balance at which the rate of drug administration approximates the rate of excretion. steady stay concentrations can be reached in about six times the drug’s elimination half-life and is independent of the actual dosage.
therapeutic index
- the ratio of the toxic dose and the therapeutic dose of a drug, which provides a measure of drug safety.
- LD50/ED50
behavioral supersensitive
upregulation
how to achieve receptor upregulation
potential consequences of receptor upregulation
how do you achieve receptor downregulation
downregulation
- given over longer periods of time