Biopharmaceutics

Question 1

what is the definition of biopharmaceutics?

Answer 1

the study of how the physiochemical properties of the drug, the dosage form and the route of administration effect the rate and extent of drug absorption

Question 2

what is the definition of pharmacokinetics?

Answer 2

the study and characterisation of the time course of drug absorption, distribution, metabolism and excretion

Question 3

what is the definition of pharmacodynamics?

Answer 3

the study of the biochemical and physiological effects of the drug on the body

Question 4

distribution is governed by affinity for various tissues, it depends on: (3)

Answer 4

• aqueous or lipid solubility
• binding to extracellular substances e.g proteins
• intracellular uptake

Question 5

what is passive diffusion and does to involve carriers?

Answer 5

• movement via concentration gradient across a membrane separating two body compartments
• does not require a carrier
• it is not saturable
• this is how the majority of drugs gain access to the body

Question 6

what is the lipid-aqueous drug partition coefficent?

Answer 6

describes the ease with which a drug moves between aqueous and lipid environments

Question 7

what is endocytosis and exocytosis? give an example

Answer 7

they are processes that mediate entry into cells by very large substances (for example: movement across intestinal wall into blood of vitamin b12 complexed with its binding protein)

Question 8

what does the therapeutic response depend on?

Answer 8

adequate concentration at the site of action

Question 9

what happens when you adjust plasma concentration?

Answer 9

it adjusts the response

Question 10

what is bioavailability?

Answer 10

a measure of the amount of drug from a formulation that appears in the plasma i.e measure of the rate and extent of absorption

Question 11

how can bioavailability be calculated?

Answer 11

by determining the AUC (area under curve) from a blood plasma drug concentration versus time plot

Question 12

what is the definition off bioequivalence?

Answer 12

comparing if two dosage forms containing same drug are equivalent in terms rate and extent of absorption

Question 13

what is absolute bioavailability?

Answer 13

Fraction of administered dose absorbed into the systemic circulation (accounting for different oral/iv doses)

Question 14

where can drugs distribute? (3)

Answer 14

• plasma (3L)
• interstitial fluid (10L)
• intracellular fluid (28L)

Question 15

what factors affect drug distribution and how? (2)

Answer 15

• aqueous or lipid solubility: only the un-ionised form will diffuse across membrane
• blood flow: parts of the body which receive the most blood flow gets the most drug

Question 16

what is the equation to work out the dose?

Answer 16

dose= vol x cons

Question 17

metabolism= ?

Answer 17

biotransformation

Question 18

what is biotransformation?

Answer 18

any process which results in a chemical change in a drug in the body

Question 19

where are metabolic processes most likely to occur? (4)

Answer 19

liver, kidneys, lungs and GI tract

Question 20

what is the process of cleavage?

Answer 20

the splitting of the molecule into 2 or more simpler molecules

Question 21

what is oxidation?

Answer 21

combining the molecule with oxygen, or increasing the electropositive charge by the loss of hydrogen or of one or more electrons

Question 22

what is conjugation?

Answer 22

the combining of the molecule with glucuronic or sulphuric acid

Question 23

what is reduction?

Answer 23

the molecule gains 1 or more electrons and become more negatively charged

Question 24

how does elimination occur in the kidneys?

Answer 24

glomerular filtration: drug crosses the glomerular filter to be excreted

Question 25

how does elimination occur in the liver?

Answer 25

changes a lipid soluble molecule to a more water soluble molecule to be excreted in the kidneys

Question 26

what is half-life?

Answer 26

the time taken for concentration to decrease to half its value