Definitions Flashcards
Concentration effect
Phenomenon by which the rise in alveolar partial pressure of nitrous oxide is disproportionately rapid when administered in high concentrations
Second gas effect
The phenomenon by which the speed of onset of inhalational anaesthetic agents is increased when administered with nitrous as a carrier gas.
Isomerism
The phenomenon where molecules with the same atomic formulae have different structiral arrangements
Structural isomerism
Identical chemical formulae with different order of atomic bonds
Tautomerism
Dynamic change between two different forms of a molecular structure depending on environmental conditions
Stereoisomerism
Identical chemical formulae and bond structure, with different 3d configuration
Enantiomers
Compounds with a single chiral centre that form non super-imposable mirror images of one another
Disteroisomers
Compounds with more than one chiral centre subject to geometric isomerism
Geometric isomerism
Two dissimilar groups linked by a double bond or ring, created due to the reduced mobility of that bond/ring
Chiral centre
central atom bound to four dissimilar groups
Enzyme
biological catalyst that increases the speed of a chemical reaction without being consumed by the reaction itself
First order reaction
Rate depends upon the concentration of the reacting components- exponential
Zero order reaction
A reaction independent of the concentration of reacting components and is therefore constant
Summation
Actions of two drugs are additive, each has an independent action
Potentiation
The action of one drug is amplified by another, which has no independent action of its own
Synergism
Combined action of two drugs is greater than would be expected from a purely additive effect
Adverse drug reaction
Occurance of any drug effect not of therapeutic, diagnostic or prophylactic benefit to the patient
Anaphylactic reaction
The response to a substance to which an individual has been previously sensitised by the formation of a specific IGE AB. It is characterised by the release of vasoactive substances and the presence of systemic symptoms (ABC)
Anaphylactoid reaction
A response to a substance not mediated by a specifiv IGE ab but characterised by the same release of vasoactive substances and presence of systemic symptoms
Ligand
Chemical messenger able to bind to a recepto
Receptor
Component of a cell that interacts selectively with a compound to initiate biochemical change or cascade to produce the effects of the compound
Kd
Molar concentration of a drug at which 50% of its receptors are occupied at equilibrium
Affinity
How avidly a drug binds to a receptor
Efficacy (IA)
A measure of the magnitude of the effect once a drug is bound
Potency
A measure of the quantity of the drug needed to produce maximal effect
Median effective concentration
Concentration of a drug that induces a specified response halfway between baseline and maximum
Median effective dose
The dose of a drug that induces a specified response in 50% of the population to whom it is administered.
Agonist
A drug that binds to a specific receptoy and once bound is able to produce a response
Antagonist
A drug with affiniity but no intrinsic activity
Full agonist
Drug that produces a maximal response
Partial agonist
A drug with significant affinity bt submaximal intrinsic activity
Competitive antagonist
Compound that competes with agonists for the same binding site
Non -competitive antagonist
A compound that binds at a different site to the natural receptor and produces a conformational distortion that prevents receptor activation
Inverse agonist
A compound that when bound produces the opposite effect to the agonist
Volume of distribution
The theoretical volume into which a drug distrubutes following its administration
Clearance
The volume of plasma from which a drug is cleared per unit time
Context sensitive half time
Time taken for the plasma concentration of a drug to fall by half after the cessation of an infusion designed to maintain a steady plasma concentration
