Pharmacokinetics

Question 1

Pharmacokinetics definition?

Answer 1

Describes what the body does to the drug in its journey from administration to elimination

Question 2

Stages of Pharmacokinetics? 5

Answer 2

-liberation
-absorption
-distribution
-metabolism
-excretion

Question 3

Liberation phases? 3

Answer 3

-disintegration (from solid to particles)
-dissolution (in site of absorption)
-permeation across GI barrier

Question 4

Absorption definition?

Answer 4

Movement of the drug from its initial point of application to the bloodstream

Question 5

Factors influencing Absorption? 7

Answer 5

-site of absorption
-GI motility (gastric emptying)
-food
-drug interaction
-malabsorption states
-pre-existing condition (CHF)
-drug formulation

Question 6

Bioavailability definition?
Consist in? 2

Answer 6

It is defined as the fraction of the administered drug that reaches the blood stream. Consists in:

-rate of absorption
-extend of adsorption

Question 7

Sustained release drug form explained?

Answer 7

It is a type of dosage form which releases an initial dose to achieve therapeutic response and a maintaining dose to achieve a prolonged response which is not constant

Question 8

Controlled release dosage form explained

Answer 8

Releases a predetermined rate of the drug in a specific period of time which is constant

Question 9

Advantages of Modified release formulations? 3

Answer 9

-reduce frequency
-better pt adherance
-more controlled plasma concentration of the drug

Question 10

Disadvantages of modified release? 2

Answer 10

-possibility of dose dumping
-dose adjusting

Question 11

When to consider bioavailability? 2

Answer 11

-change rout of administration
-same drug with different formulation

Question 12

Factory’s influencing bioavailability? 3

Answer 12

-pt
-drug
-formulation

Question 13

Distribution definition

Answer 13

Refers to the movement of the drug around the body.

Question 14

Factors affecting distribution? 4

Answer 14

-protein binding
-tissue binding
-blood flow to tissue
-drug Lipid solubility

Question 15

Volume of distribution definition and formula?

Answer 15

Indicated how widely the drug is distributed in the body tissue compared to the plasma.
>VD >concentration of the drug in the tissue
Vd=dose : concentration drug in plasma

Question 16

Loading dose purpose ?

Answer 16

Flood the tissue with the drug to obtain a therapeutic effect sooner

Question 17

Steady state concentration definition?

Answer 17

It is defined as the time in which the concentration of the drug remain constant when the drug is given continuously and repeatedly.

Question 18

Steady state concentration and volume distribution relation

Answer 18

Before reaching Css the drug concentration depends on the Vd of the drug

After reaching Css the concentration depends on:
-metabolism
-excretion

Question 19

Loading dose formula

Answer 19

Loading dose= target conc x Vd

Or (target conc x Vd) : Fs

Question 20

Plasma Protein binding definition

Answer 20

Refers to the degree to which the drug is bound to the plasma protein.

Question 21

Metabolism definition?
Where occurs?

Answer 21

Chemical alteration of the drug which occurs in the liver or small intestine epithelium

Question 22

Factors affecting metabolism? 3

Answer 22

-hepatic blood flow
-hepatic disease
-enzyme altering the liver functioning

Question 23

Phase 1 metabolism explained

Answer 23

Occurs in zone 3 of hepatocyte. Enzyme involeved Cyt450p and Cyp3A. Chemical alteration involves:
Oxidation (most common)
Hydrolysis
Reduction

Result:
Molecule becomes active
Molecule becomes less active
Molecule becomes inactive

Question 24

Metabolism phase 2 explained

Answer 24

Chemical alteration of the drug or it’s metabolite in which a ionisable group is added to make the drug more easy to eliminate via the process of conjugation

Question 25

Examples of metabolism phase 2? 6

Answer 25

Glucoronidation
-glycosidation
-sulphation
-methylation
-Acetylation
-gluthathionation

Question 26

Functional unit of the liver?

Answer 26

Hepatic acini

Question 27

Portal triad consist in?

Answer 27

-portal vein
-hepatic artery
-bile duct

Question 28

Describes how the drug is metabolised in the liver?

Answer 28

From the portal triad the drug reaches the central vein passing through hepatocyte when phase 1 metabolism occurs (zone 3). Zone 3 is more susceptible of drug induced toxicity

Question 29

Extraction rate definition and formula

Answer 29

Fraction of the drug eliminated from the bloodstream by the liver

(Cin -Cout) : Cin

Question 30

Excretion definition

Answer 30

Elimination of the drug (chemically changed or its metabolites) from the body

Question 31

Zero order elimination explained?

Answer 31

Refers to the elimination of a constant quantity of drug per time unit of the drug quantity present in the organism

Question 32

First order elimination explained.
Correlation with Vd
With formula?

Answer 32

Refers to the elimination of a constant fraction of drug per time unit of the drug quantity present in the organism

In the first order elimination the rate of elimination and the plasma concentration of the drug are proportional. This is explained with this formula
Kel = clearance : Vd

Question 33

Half-life definition

Answer 33

Refers to the time in which the drug concentration fall by 50% by its original concentration

Question 34

AUC Area under the curve refers to?

Answer 34

gives an insight in the extent of exposure to the drug and the clearance rate

AUC= daily dose : clearance

Question 35

Zero order kinetics explained

Answer 35

Occurs when a drug with limited capacity metabolism reaches saturation non metabolic enzyme.
The clearance value decreases as the plasma concentration increases.