3.14/3.15 Pharmacokinetics II

Question 1

what are things that can influence absorption?

Answer 1

• molecular size
  solubility
  degree of ionization

Question 2

large Ka = _____ acid because?

Answer 2

strong, bc it largely dissociates

Question 3

lower pH relative to pKa = greater fraction of ______

Answer 3

drug in protonated form

Question 4

factors that affect distribution of drugs

Answer 4

-rate of blood flow
- concentration gradient
- ability to exit vascular system
- ability to penetrate tissue

Question 5

4 sites of drug concentration

Answer 5

1. fat (lipid soluble drugs)
2. tissue
3. bone (tetracyclines)
4. trans-cellular reservoirs (GI)

Question 6

An active drug is a ______ drug

Answer 6

free

Question 7

_____ is the minimum concentration required for drug effect

Answer 7

MEC

Question 8

__________ is the minimum concentration at which toxicity usually occurs

Answer 8

MTC

Question 9

biotransformation happens in the _____

Answer 9

liver

Question 10

what is the equation for TW?

Answer 10

TW = MTC/MEC

Question 11

factors that determine intensity of drug response

Answer 11

diet, co-morbitiy, age, weight, drug-drug interaction, genetics

Question 12

what things influence metabolism?

Answer 12

Phase 1 reactions, Phase 2 reactions, genetic factors, induction of drug metabolism, inhibition of drug metabolism

Question 13

_________ is oxidation, reduction, hydrolysis of a drug

Answer 13

phase 1 biotransformation

Question 14

oxidative processes usually involve what kind of enzymes?

Answer 14

cytochrome P450 system

Question 15

_____________ consists of synthesis reactions where something is added to molecule

Answer 15

Phase 2 Biotransformation:

Question 16

_______ makes drugs more water soluble and more excretable

Answer 16

Conjugation

Question 17

__________ makes drugs less water soluble and inactivates drug

Answer 17

Acetylation/methylation

Question 18

what are cytochrome P450 enzymes?

Answer 18

family of super enzymes pivotal in metabolism of drugs/chemicals

Question 19

where are Cytochrome P450 enzymes found?

Answer 19

Smooth ER

Question 20

what do Inducers do?

Answer 20

• increase enzyme levels
• speed up metabolism
• lower plasma levels below MEC
• can be drugs or environmental pollutants

Question 21

what do inhibitors do?

Answer 21

• slow metabolism
• can cause drugs to accumulate at toxic levels
• can be drugs, foods, chemicals
• decreases enzyme activity
  EX: grapefruit = inhibitor of cytochrome P450 CYP3A4

Question 22

factors that affect drug bioavailability

Answer 22

first pass effect, drug-drug interaction

Question 23

3 types of drug-drug interaciton

Answer 23

additive, synergism, potentiation

Question 24

3 routes of drug excretion

Answer 24

renal, non-renal, ion-trapping

Question 25

___________ is the time required to change the amount of drug in the body by one half during elimination

Answer 25

half life

Question 26

equation for half life

Answer 26

t1/2 = (0.7 x Vd)/CL

Question 27

_________ is the removal of drug from systemic circulation

Answer 27

Clearance

Question 28

clearance equations (3 of them)

Answer 28

CL = (rate of removal of drug)/(plasma concentration of drug) CL = dose/ AUC CL = (.7 x Vd)/ t1/2

Question 29

what happens after 4-5 half lives

Answer 29

plasma concentrations of a given drug will be below a clinically relevant concentration and thus will be considered eliminated.

Question 30

______ is a constant fraction of drug metabolized per unit of time (most drugs)

Answer 30

First order kinetics (straight log graph)

Question 31

__________ is a constant amount of drug is metabolized per unit of time (ethanol/phenytoin)

Answer 31

Zero order kinetics curved line on log graph

Question 32

what does the 2 compartment model show?

Answer 32

drug can be exchanged between extravascular volume, blood or excreted

Question 33

A ______ is an initial higher dose of a drug that may be given at the beginning of a course of treatment before dropping down to a maintenance dose. useful for drugs that are eliminated from the body relatively slowly (have a long systemic half-life)

Answer 33

Loading dose

Question 34

loading dose equation

Answer 34

LD = (Vd x Desired plasma concentration) / Bioavailabilty

Question 35

A ______ is when drug levels are maintained above the MEC to maintain a steady state of drug in the body

Answer 35

Maintenance dose

Question 36

equation for Maintenance dose

Answer 36

MD = (dosing rate) x (dosing interval)

Question 37

what are the 5 factors that influence elimination

Answer 37

pH dependent ionization (ion trapping) competition for tubular transport age disease drug interactions

Question 38

weak acids/bases can only cross membrane in _______ form

Answer 38

unionized

Question 39

_________ relates amount of drug in body to plasma concentration

Answer 39

Apparent volume distribution (Vd)

Question 40

larger Vd means what?

Answer 40

more likely to leave plasma and enter extravascular compartments of body

Question 41

_______ is the fraction (F) of drug that reaches systemic circulation

Answer 41

Bioavailability

Question 42

bioavailability equation

Answer 42

F = (amt reaching systemic circulation)/(amt administered)

Question 43

_______ makes drugs more water soluble and more excretable

Answer 43

Conjugation