PK of Oral Absorption

Question 1

True or false: absorption alters onset, intensity, and duration

Answer 1

true

Question 2

Which processes is Ka the net result of?

Answer 2

disintegration and dissolution of drug
gastric emptying rate and intestinal motility
transport across membrane
splanchnic blood flow

Question 3

What is Ka?

Answer 3

absorption rate constant
-fraction of drug present at absorption site absorbed per unit time
-higher the Ka=faster absorption rate

Question 4

Differentiate between absorption rate and absorption rate constant.

Answer 4

absorption rate:
-amount of drug absorbed per unit time
-values change as amount changes in the body
absorption rate constant:
-fraction of dose absorbed per unit time and has units of reciprocal time
-values do not change for a drug regardless of dose size

Question 5

What are the parameters which determine Tmax?

Answer 5

Ka and K
time to reach maximum plasma concentration

Question 6

What are the parameters which determine Cmax?

Answer 6

dose
Vd
F
Ka
K
(and Cls since K=Vd/Cls)

Question 7

True or false: Ka impacts AUC

Answer 7

false

Question 8

What is lag-time?

Answer 8

time delay prior to commencement of first-order absorption

Question 9

What are the factors which contribute to lag time?

Answer 9

delay in gastric emptying
formulation factors

Question 10

What is flip-flop kinetics?

Answer 10

situation where Ka<K and the slope of log linear terminal portion does not equal K, it equals Ka

Question 11

How can you determine if a drug shows flip-flop kinetics?

Answer 11

compare the Cp vs t of oral to IV
-if the terminal slopes are parallel, terminal slope=K
-if the terminal slopes arent parallel, terminal slope=Ka

Question 12

What is the goal of controlled release products?

Answer 12

overcome problem of frequent dose administration for drugs with short t1/2

Question 13

What is bioavailability?

Answer 13

rate and extent of therapeutically active drug that reaches the systemic circulation
-fraction of dose of parent drug reaching the systemic circulation intact
-value ranges from 0-1 (or 0-100%)

Question 14

What is the multiplicative function of F?

Answer 14

fraction of drug that makes it sequentially from the GI lumen, through the GIT wall, into the portal circulation, through the liver and into the general circulation
F=Ff x Fg x Fp x Fh

Question 15

Differentiate absolute bioavailability and relative bioavailability.

Answer 15

absolute bioavailability
-comparison of AUCs after oral and IV admin in the same person on diff occasions
relative bioavailability
-F of a drug product relative to a recognized standard

Question 16

Which drugs demonstrate flip-flop kinetics?

Answer 16

controlled-release