FoM:L5 - Pharmacokinetics, calculations

Question 1

What is the equation used to calculate bioavailability?

Answer 1

administered dose (D) x bioavailability (F)

Question 2

What is zero order kinetics?

Answer 2

• enzymes are saturated
• rate of elimination rate is fixed
• constant amount of drug is eliminated per unit time

Question 3

What is the rate for elimination of alcohol?

Answer 3

1 unit per hour

Question 4

What is first order kinetics?

Answer 4

• same proportion of drug falls each unit of time
• constant half life

Question 5

Outline drug clearance

Answer 5

• organ of elimination clears a proportion of the drug
• gradually cleared, plasma conc falls
• drug in plasma reduces, so elimination rate is reduced
• constant

Question 6

What is clearance?

Answer 6

volume of blood from which all the drug is cleared per unit of time (e.g. mL/min or L/h) in a particular organ

Question 7

How do you calculate the clearance?

Answer 7

rate of elimination / plasma concentration

Question 8

How do you calculate rate of elimination?

Answer 8

total clearance x plasma concentration

Question 9

How would you work out administered dose at steady state?

Answer 9

total clearance x plasma concentration

Question 10

Give the equation used in maintenance dosing

Answer 10

oral dose x oral bioavailability / time interval = clearance x plasma concentration

Question 11

How do you calculate loading dose?

Answer 11

loading dose = Vd x plasma conc. / F