Issar -Quantitiative PK

Question 1

Describe 0 order rxn

Answer 1

The rxn proceeds at a constant rate and is independent of the conc. of drug present in body. Ex: alcohol
*non linear pharmakokinetics

Question 2

Describe 1st order rxn

Answer 2

Rxn proceeds at rate dependent on drug concentration.

Question 3

When drug conc is low it typically is a ___ order rxn

Answer 3

first

Question 4

what is mixed order/non linear kinetics

Answer 4

when drugs convert from first order to 0 order kinetics and occurs when the rate limiting step or enzyme becomes saturable at concs approximating the range of therapeutic conc’s

Question 5

What is a compartment. What assumption are they based on? is it an open or closed system

Answer 5

not a real anatomic region but is considered as a tissue or group of tissues that have similar blood flow and drug affinity. Within each compartment, the drug si considered to be uniformely distributed. Compartments are based on linear assumption and are an open system bc drug can leave the system

Question 6

What refers to well stirred

Answer 6

mixing of a drug within a compartment

Question 7

What are assumptions of the one compartment linear model

Answer 7

1. drug achieves distribution throughout the body and the drug equilibrates instantaneously between tissues and the drug conc profile shows monophasic response.
2. drug is mixed instantaneously in blood or plasma
3. drug elim follows first order kinetics

Question 8

First order kinetics is an assumption of a ____ model, not a compartment model

Answer 8

linear

Question 9

Describe the two compartment model

Answer 9

Resolves body into a central compartment and a peripheral compartment

Question 10

what are assumptions of two compartment model

Answer 10

1. central compartment = heart, lungs, kidneys, liver, and brain (highely perfused tissues)
2. peripheral compartment = muscle, fat, and skin
3. drug admin into the central compartment distributes bet central and peripheral but doesnt achieve instantaneous distribution

Question 11

Clearance does not indicate how much drug is being removed…the units of clearance are generally ____/min

Answer 11

ml

Question 12

what is half life; when is it meaningful?

Answer 12

refers to the time it takes for the plasma conc. of the drug to fall by 50% regardless of the initial value. Most meaningful when the drug is eliminated according to first order kinetics

Question 13

Length of half life is _____ and is shortened by a ____ in volume of distribution or an ____ in clearance. _____ administered does not affect half life

Answer 13

constant; decrease; increase; dose

Question 14

what is steady state referred to; what does it depend on?

Answer 14

is the condition when the rate of drug entry into the body is balanced by the rate of elimination and no further accumulation occurs; only depends on half life! not on dose!

Question 15

Loading ____ helps us achieve therapeutic window faster; esp for drugs that have a long half life. A drug with a ____half life will achive Css rapidlly compared to a drug with a long half life

Answer 15

dose; short

Question 16

what are 3 factors that influence extent of fluctuations in drug concentration

Answer 16

1. half life
2. dose division
3. dose form

Question 17

___half life produces more fluctuations

Answer 17

short

Question 18

___ release can very effectively decrease the fluctuations in concentration

Answer 18

slow

Question 19

what is a practical way to restrict fluctuation

Answer 19

1. give drug at shorter intervals (4 x a day)

2. sustained release formulation (given 2 x day)