Drug Clearance

Question 1

What is the definition of clearance?

Answer 1

The volume of plasma cleared ENTIRELY of drug per unit time.

Question 2

What is the unit of clearance?

Answer 2

mL / min

L / hr

Question 3

What is the link between concentration and elimination rate?

Answer 3

elimination = clearance X plasma concentration

Question 4

What is the equation for clearance total?

Answer 4

CLEARANCE (hepatic) + CLEARANCE (renal) + CLEARANCE (other)

Question 5

How do you work out the amount in the body (mg)?

Answer 5

VOLUME (litres) X CONCENTRATION (mg / litres )

Question 6

How do you work out the initial concentration (mg / L)?

Answer 6

Dose (mg) / Volume (litres)

Question 7

How do you work out the concentration at time (t)?

Answer 7

𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑎𝑡 𝑡𝑖𝑚𝑒 𝑡=𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 × 𝑒^(−𝐶𝐿/𝑉 𝑡)

Question 8

How do you work out the half life?

Answer 8

𝐻𝑎𝑙𝑓 𝑙𝑖𝑓𝑒=(ln⁡(2)𝑉)/𝐶𝐿

Question 9

How do you work out the constant rate infusion?

Answer 9

Concentration = infusion rate / CL

Question 10

What is the drug that gives continuous infusion?

Answer 10

Vancomycin (antibiotic) and targets a concentration of 15 - 25 mg/L

Question 11

What is the condition required for clearance?

Answer 11

Clearance is ONLY constant if the elimination process is NOT saturated.

Question 12

List the processes which contribute to the total body clearance of a drug.

Answer 12

Renal / Hepatic / Gut / Breast Milk / Tears / Sweat / Breath