Basic pharmacologic principles

Question 1

pharmacokinetics

Answer 1

relationship between drug dose and drug concentration in plasma or site of drug effect over time
governed by absorption, distribution, and elimination

Question 2

biophase

Answer 2

time delay between changes in plasma concentration and drug effect; affected by solubility

Question 3

effect site concentration

Answer 3

mathematically-derived virtual location where anesthetic drug exerts its effect

Question 4

front-end kinetics

Answer 4

description of IV drug behavior immediately following administration, including rapidity of distribution and elimination
phases: rapid dist, slow dist, terminal/elimination

Question 5

back-end kinetics

Answer 5

description of IV drug behavior when administered as continuous infusion, including time period after termination of infusion
includes decrement time and context-sensitive half time

Question 6

context-sensitive half time

Answer 6

description of time required for drug concentration to decrease by 50% after termination of drug infusion, based on duration of infusion (context)

Question 7

pharmacodynamics

Answer 7

description of what the drug does to the body, including the relationship between drug concentration and pharmacologic effect

Question 8

dynamic range

Answer 8

the drug concentration range in which changes in drug effect occur. Drug levels below the DR are ineffective; levels above the DR do not provide additional effect.

Question 9

equation: volume of distribution
equation: Vd at time t

Answer 9

amount of dose (mg) / concentration (mg/L)

amount (t) / concentration (t)

Question 10

What determines peripheral volume of distribution?

Answer 10

Solubility; more soluble = larger peripheral Vd

Protein binding; more binding = larger Vd

Question 11

clearance

Answer 11

rate of drug removal from the plasma/blood, defined in units of flow (volume per unit time)
2 processes: systemic and intercompartmental

Question 12

systemic clearance

Answer 12

permanent removal of drug from the body by elimination or transformation into metabolites

Question 13

intercompartmental clearance

Answer 13

moving drug between peripheral and plasma compartments

Question 14

equation: clearance (3)

Answer 14

dA/dt / C(t) [rate of elim at time t / conc at time t]

Q(Cin-Cout) / Cin [Q=blood flow to metabolic organs. Cin/out=conc delivered and leaving organs]

Q x ER [ER=extraction ratio, (Cin-Cout)/Cin]

Question 15

flow limited vs capacity limited clearance

Answer 15

flow limited = change in blood flow -> decreased clearance

capacity limited = change in organ ability to process, d/t disease or enzymatic induction

Question 16

hysteresis

Answer 16

two different plasma concentrations correspond to one drug effect, or one plasma concentration corresponds to two drug effects

Question 17

potency

Answer 17

amount of drug required to elicit an effect, commonly described by C50, smaller C50 = more potent but longer time to onset since fewer molecules to bind

Question 18

efficacy

Answer 18

drug effectiveness once occupying a receptor, determined by full vs partial agonism/antagonism

Question 19

additive, antagonistic, and synergistic drug interactions

Answer 19

additive: co-administered drugs effect = sum of parts
antagonistic: effect less than additive
synergistic: effect more than additive

Question 20

equation: IBW

Answer 20

male: 50kg + 2.3kg(# inches over 5 feet)
female: 45.5kg + 2.3kg(# inches over 5 feet)

Question 21

equation: corrected body weight

Answer 21

IBW + 0.4x(TBW-IBW)

Question 22

drugs affecting liver clearance of drugs

Answer 22

cyp450 and cyp3A4
inducers: glucocorticoids, carbamazepine, barbiturates, rifampin

inhibitors: antifungals, some abx (clinda), SSRIs, grapefruit juice

Question 23

primary reactions of hepatic clearance

Answer 23

hydroxylation and reduction

Question 24

therapeutic index

Answer 24

LD50 - ED50
effective and lethal doses
larger TI is better

Question 25

Use of IBW vs TBW

Answer 25

most induction meds are based on IBW, except succinylcholine

most infusions are based on actual TBW

Question 26

vessel-rich group components, % body mass, and % cardiac output

Answer 26

brain, heart, liver, kidney, endocrine glands

10% mass, 75% CO

Question 27

muscle group components, % body mass, and % cardiac output

Answer 27

muscle, skin

50% mass, 19% CO

Question 28

fat group components, % body mass, and % cardiac output

Answer 28

fat

20% mass, 6% CO

Question 29

vessel-poor group components, % body mass, and % cardiac output

Answer 29

bone, ligament, cartilage

20% mass, 0% CO