Pharmacology equations

Question 1

What two ways can we calculate clearance?

Answer 1

(Urinary concentration of drug in mls x ml of urine produced per min) / plasma concentration

Cl = Vd x k

Question 2

How do we calculate concentration?

Answer 2

Dose/volume

Question 3

What is the main equation for an exponential function?

How does this relate to first order kinetics?

What are the relevant associated numbers?

Answer 3

(Delta concentration / delta time) = k x C

C = C0.e to the power of -kt for a negative exponential e.g. first order

E = 2.718
K = 0.693
1/e = 0.37

Question 4

What 2 ways can we calculate the time constant?

What are the different time constant drops?

Answer 4

Tau = 1/K

Tau = Vd / cl

1 = 63
2 = 86
3 = 95
4 = 98

Question 5

How do we calculate the half life and how do we rearrange this?

Answer 5

T 1/2 = k x (Vd/Cl)

Cl = k x (Vd/ t1/2)

Question 6

How do we calculate loading dose?

And maintenance dose?

Answer 6

Loading dose = volume of distribution x plasma concentration

Maintenance dose = cp x cl

Question 7

How do we calculate oral dose?

Answer 7

(Cl x cp x dose interval) / bioavailability fraction

Dose interval = duration
BF is written as 100% = 1, 90% = 0.9 etc.

Question 8

How do we calculate how many ml of volatile will produce 22.4 L?

Answer 8

MW / density

Question 9

How do we calculate the amount of nitrous left in a cylinder?

Answer 9

((Weight of cylinder - tare) / 44) x 22.4

Question 10

How do we calculate the amount of O2 left in a cylinder?

Answer 10

Volume = ((guage pressure plus atmospheric) x volume of cylinder)) / atmospheric pressure

Uses Boyles law

Question 11

How do we calculate elimination?

Answer 11

Concentration (steady state or not) x clearance