Calculations

Question 1

You are trying to find the half life of a drug.

1. What equation do you use to find the clearance CL of a drug?
2. Now, what equation do you use to find the half life of a drug?

Answer 1

CL= (rate of elimination)/(drug plasma concentration)

t1/2=(0.693xVd)/CL

Question 2

How do you calculate the therapeutic index?

Answer 2

[Min toxic]/[Min therapeutic]

Question 3

How do you calculate oral bioavailability?

Answer 3

[oral route drug reached systemic circulation]/[iv route drug reached systemic circulation]x100

Question 4

How do you calculate Vd (L/Kg)?

Answer 4

Dose(mg)/Css (mg/L) = X L

X/weight(kg) = Vd L/kg

Question 5

How do you calculate steady state of plasma concentration Css?

Answer 5

(Dose x F)/(Hz of administration x CL)

D x F)/(t x CL

Question 6

How do you calculate renal clearance?

Answer 6

Drug concentration x blood flow x percentage cleared

Question 7

How do you calculate loading dose?

Answer 7

Css x (Vd/F)

Question 8

Drug 1 has a Vd of 0.12 L/kg.

Bob weighs 75kg

What is his Vd in L?

Answer 8

0.12x75=9L