General Pharma (pharmacokinetics)

Question 1

What is pharmacokinetics?

Answer 1

It means the movement of the drug within the body and includes drug absorption, distribution, metabolism and excretion.

Question 2

What is meant by bioavailability?

Answer 2

Bioavailability refers to the fraction of the drug that reaches the systemic circulation from a given dose.

Question 3

What are the factors that effect bioavailability?

Answer 3

1 - Factors that affect drug absorption
2 - First pass metabolism
3 - Enterohepatic cycling
4 - Hepatic diseases

Question 4

What is meant by drug distribution?

Answer 4

Drug distribution can be defined as the reversible transfer of drugs between body fluids compartments.

Question 5

What is meant by drug absorption?

Answer 5

The movement of a drug from the site of administration into the blood stream is known as absorption.

Question 6

What factors influence drug absorption?

Answer 6

1) Physiochemical properties
2) Route of drug administration
3) pH and ionisation
4) food
5) presence of other drugs
6) area of absorbing surface
7) gastrointestinal and other diseases

Question 7

What is apparent volume of distribution?

Answer 7

(aVd) Apparent volume of distribution is defined as the hypothetical volume of body fluid into which a drug is uniformly distributed at a concentration equal to that in plasma, assuming the body to be a single compartment.

aVd = Total amount of drug in body/Concentration of the drug in plasma

Question 8

Drugs that are highly bound to plasma protein have a ___ volume of distribution

Answer 8

Low

Question 9

Plasma protein binding ___ the metabolism of drugs

Answer 9

Delays

Question 10

Excretion of plasma protein bound drugs is _____

Answer 10

Delayed

Question 11

Highly protein bound drugs have a ____ duration of action.

Answer 11

Longer

Question 12

What is biotransformation (drug metabolism)

Answer 12

Chemical alteration of the drug in a living organism is called biotransformation.

Question 13

What are the main sites for drug metabolism (biotransformation)?

Answer 13

Liver is the main site for drug metabolism; other sites are GI tract, kidneys, blood, skin and placenta.

Question 14

What is the end result of drug metabolism (biotransformation)?

Answer 14

Inactivation, but sometimes a compound with pharmacological activity may be formed.

Question 15

List the uses of prodrugs.

Answer 15

1) To improve bioavailability
2) To prolong duration of action
3) To improve taste
4) To provide site specific drug delivery

Question 16

Name the phase one reactions and the drugs that undergo them.

Answer 16

Oxidation - Phenytoin, phenobarbitone, pentobarbitone and propranolol
Reduction - Chloramphenicol, Methadone
Hydrolysis - Esters: Procaine, succinylcholine. Amides: Lignocaine and procainamine
Cyclisation - Proguanil
Decyclization - phenobarbitone and phenytoin

Question 17

Name phase II reactions, their enzymes and the drugs that undergo them

Answer 17

1) Glucuronidation/ UDP glucuronosyl transferase/ Aspirin and Morphine
2) Acetylation/ N-acetyltransferase/ Isoniazid and Dapsone
3) Sulphation/ Sulphotranferase/ Paracetamol and Methyldopa
4) Methylation/ Transmethylase/ Adrenaline and Dopamine
5) Glutathione conjugation/ Glutathione transferase/ Paracetamol
6) Glycine conjugation/ Acyl CoA glycine transferase/ Salicylates

Question 18

List the bioavailability for various routes:
> I/V :
> Transdermal : 
> I/M : 
> Subcutaneous :
> Rectal : 
> Oral or Inhalational route :

Answer 18

> I/V : 100%
> Transdermal :  80% - < 100%
> I/M :  75% - < 100%
> Subcutaneous :  70% - < 100%
> Rectal :  30% - 70%
> Oral or Inhalational route :  5% - <100%

Question 19

Name three drugs with a low volume of distribution

Answer 19

Tolbutamide - 7L
Furosemide - 8L
Warfarin - 10L

Question 20

Name three drugs with a high volume of distribution

Answer 20

Digoxin - 500L
Imipramine - I600L
Chloroquine - 13000L

Question 21

Name drugs which are highly bound to plasma proteins

Answer 21

> Warfarin = 99% bound
Furosemide = 98% bound
Phenylbutazone = 98% bound
Cloxacilin = 95% bound

Question 22

Name drugs less commonly bound to plasma proteins

Answer 22

> Amoxicillin = 18% bound
Ethosuximide = 0.0% bound
Acetaminophen

Question 23

Name plasma proteins that bind drugs

Answer 23

Albumin, alpha1 - acid glycoprotein, lipoproteins, steroid hormone binding globulin, thyroxin binding globulin

Question 24

What is enzyme induction?

Answer 24

Enzyme induction occurs when repeated administration of certain drugs lead to the increased synthesis of microsomal enzymes. E.g phenytoin, barbiturates, griseofulvin, rifampin