4 - Hemodialysis

Question 1

What are the factors for predicting if a drug will be removed during hemodialysis?

Answer 1

• MW > 5000 daltons will generally not be easily removed
• High protein bound drugs (> 90-95%) are typically not easily removed
• Drugs w/ large Vd (> 1 L/kg) are typically widely distributed (less in plasma) and therefore have less removal
• Drug will be removed more extensively by “high flux” hemodialysis, if dialysis session is 4 h, and if blood flow rates are 300 mL/min or higher

Question 2

What is the dosing of valacyclovir for hemodialysis?

Answer 2

500 mg q24h

Question 3

What equation is used to calculate concentration after administration of a drug, if given as an infusion?

Answer 3

C time = [Ro (1 - e^-ke*t)] / [Vd * ke]

• t = infusion time
• Ro = infusion rate (mg/h)

Question 4

What equation is used to calculate concentration after a certain amount of time? (Ex: the concentration of drug just before the next hemodialysis session)

Answer 4

C time = C initial * e^-ke*t

- t = time since end of infusion

Question 5

Sensitivity/ resistance to oxacillin = S/ R to _____

Answer 5

Cefazolin

Question 6

How do you calculate maintenance dose for a pt on hemodialysis?

Answer 6

• Calculate the concentration right after dialysis (should be the lowest it will ever go)
• Calculate concentration after administration of the drug (should be the highest it will ever go)
• Take concentration after administration and subtract concentration after dialysis to get the difference, then multiply this concentration by Vd to get a dose in mg

Question 7

What equation is used to calculate concentration after administration of a drug, if given as a bolus?

Answer 7

C = dose/Vd

Question 8

Can a drug be given during the dialysis session to save time?

Answer 8

Yes, but give it at the last possible time (ex: if drug needs 1 h infusion time, give 1 h before dialysis session ends)