pharmacodynamics

pharmacodynamics

study of biochemical and physiological effectof drugs and their mechanism of action

pharmacodynamics

deals w the action of drugs within the body

drug

broadly defined as any chemical substance that affects living processes

receptors

class of drugs w which they interact and the effect that can be induced on them

action of the drug

initial consequence of a drug receptor interaction

drug effects

succeeding events of action of drugs

drug effect

what is produced by the drug

drug action

where and how the effect is produced

drug receptor

molecules to which a drug has affinity

ligand

any drug or substance with specific affinity to a receptor

agonist

drug which by acting on their receptor and mimics the effects of these endogenous compounds

antagonist

drug which combines specifically with receptors and block the action of the agonist

receptors

located either on the surface of cells or within the cells which occupies a tiny portion of the cell

chelation

formation of coordinating complexes through ring system

edta

binds with lead

penicillamine

binds with copper

carriers

also termed membrane transport proteins

the target sited for many drugs

Na+/K+/2Cl- symport in the nephron

the target site of action for furomeside

drug activity

when a drug molecule interacts with a drug-receptor, a drug complex is formed

affinity

efficacy

basic requirements for drug activity

affinity

ability of drug to bind with the receptor

efficacy

intrinsic activity of the drug

drug activity

ability of the drug to cause alteration in the biologic system

muscarinic receptor activation

primarily associated with parasympathetic activity

covalent bond

two atoms share a pair of electrons

covalent bond

can be broken at very high temperature or with the intervention of a catalytic enzyme

ionic bonds (positive and negative)

results from the electrostatic attraction between oppositely charged ions

hydrogen bond (H bond)

ability of a proton (H+) to accept an electron pair; one from donor (e.g. oxygen) and the other from another donor

hydrogen bond (H bond)

much weaker than a covalent bond

intermolecular forces (van der Waals forces)

form very weak bonds between dipoles or induced dipoles

van der Waals forces

believed to play a major role in determining that specificity of drug receptor interaction

agonist

defined as a drug that possesses affinity for a particular kind of receptor and the ability to cause a change in the receptor that give rise to an observable effect

affinity and efficacy

two variables that composed drug action

affinity

concentration required to produce a half maximal response

efficacy

magnitude of the maximal response

partial agonist

combines with the receptor but is of lower efficacy that the agonist

antagonist drugs

drug that interacts with the receptor or other component of the effector mechanism to inhibit action of an agonist

competitive antagonism

based on the competition between the antagonist and an agonist for the receptor to which both have affinity

non-competitive antagonist

inhibits the action of an agonist by binding at a site other than the binding of the agonist to receptor

pharmacologic antagonist

the antagonist drug interferes with the mechanism by which most pharmacological effects are produce

physiologic antagonist

two agonists acting at different sites counterbalance each other by producing opposite effects on the same physiological function

biochemical antagonist

occur whenever one drug indirectly decreases the concentration of the second drug at it site of action

chemical antagonist

chemical inactivation or neutralization

dualist

refers to a drug having both agonistic and antagonistic properties

dualist

the intrinsic activity of a drug can have any magnitude between zero and maximum

additive effects

occurs if two drugs with the same effect, when given together produces an effect that is equal in magnitude

synergism

occurs if two drugs with the same effect, when given together, produce an effect that is greater in magnitude

eab >ea +eb

potentiation

occurs if a drug lacking an effect of its own increases the effect of a second active drug

eab=ea+<eb

potency

refers to the dose that must be administered to produce particular effect of given intensity

margin of safety

referred to as the therapeutic index and is obtained from the ratio of median lethal dose to the median effective dose

median effective dose

the dose (minimal) of a drug required to produce a predetrmined response in 50% of the animal

medial lethal dose

when death is a response, a in lethal toxicity studies

median toxic dose

dose that produces toxic effect but no death incurred

selectivity

depends on its capacity to preferentially produce a particular effect

specificity

when all effects produced by a drug are due to single, mechanism of action