Introduction to Biopharmaceutics

Question 1

Biopharmaceutics is..

Answer 1

The study of how physiochemical properties of drugs, dosage forms and routes of administration affect the rate and extent of drug absorption.

Question 2

Why is Biopharmaceutics important?

Answer 2

There is a knock on effect on the drug, and in turn - the patient.

Question 3

What does the body to the drug? (4)

Answer 3

ADME

Absorption
uptake into system

Distribution
transfer to body fluids and tissue

Metabolism
transform into metabolites

Excretion
removed

Question 4

How can we know the amount of drug in the body?

Answer 4

Plasma concentration

The higher the plasma concentration, the higher drug concentration.

Question 5

What is the Therapeutic window?

Answer 5

The minimum effective concentration.

Question 6

C max (plasma conc max), what would this be in IV administration?

Answer 6

Same as plasma drug concentration at 0 because no absorption phase.d

Question 7

What is the Toxic range?

Answer 7

The minimum toxic concentration.

Question 8

Why are repeated doses needed?

Answer 8

Because plasma concentration decreases over time and fall before therapeutic range.

Question 9

What is the onset of time?

Answer 9

The time where the plasma concentration first exceeds the therapeutic window.

Question 10

What is AUC?

Answer 10

the exposure of the body to the drug.

Question 11

Equation for AUC

IV administration

Answer 11

Co (initial conc) / elimination rate constant

Question 12

What is the plasma half life?

Answer 12

Time taken for the plasma concentration of a drug to fall by 50%

Question 13

Equation for plasma half life:

Answer 13

t1/2 = t2 - t1

Question 14

Is the plasma half life constant?

Answer 14

Yes because it follows first order kinetics.

Question 15

Long plasma half life means…

Answer 15

more time can pass before taking a second dose.

Question 16

What is the volume of distribution?

Answer 16

an indication of how likely a drug is to remain in the body or go into tissues.

Question 17

Equation for volume of distribution:

Answer 17

Vd = D / Co

D = IV dose (mg)
Co = initial plasma conc mg per L

Question 18

Clearance is…

Answer 18

the volume of plasma from which the drug is eliminated per unit time L per H.

hepatic and renal clearance.

Question 19

Equation for AUC in oral administration:

Answer 19

D x F / CL

D = dose
F = bioavaliability
CL = clearence

Question 20

Bioavaliability, F, is..

Answer 20

the fraction of the dose that reached systemic circulation.

Question 21

What is F in IV administration?

Answer 21

1 or 100%

Question 22

What is F in oral administration?

Answer 22

F < 1 due to pre-systemic effects

Question 23

How can food affect drugs?

Answer 23

Affects drug stability, dissolution and absorption due to food components which may stimulate enzyme activity (this causes breakdown of drug before it reaches target)