Renal Dosing in Renal Failure

Question 1

Can Renal fucntion lead to problems with absoportion of drugs?

Answer 1

There is little data to suggest such a thing; possibly delayed Tmax and slightly lower Cmax

Question 2

Can Renal function lead to changes in distribution?

Answer 2

Yes; Vd changes with total ody water and protein binding and tissue binding; inc of total body water can inc Vd of hydrophilic drugs

Question 3

How is plasma protein binding affected in renal problems?

Answer 3

protein binding to albumin is by acidic drugs and can be affected by dec in uremia; it inc fraction of unbound drug

Question 4

If a drug is less bound to the plasma proteins do you need more or less of a dose?

Answer 4

I dont know. I think if you have more free in plasma you need to initially lower the loading dose

Question 5

What is the equation to adjust for Cp in low albumin pts?

Answer 5

Cp(obs / (0.48*0.9)(alb/4.4) + 0.1

Question 6

Does the kidney have CYP enzymes?

Answer 6

Yes 20% the power of the liver

Question 7

When you have kidney problems you have decreased metabolism and accumulation of the parent drug, T or F?

Answer 7

True

Question 8

Renal clearance is a function of glomerular filtration, tubular secretion and reabsorption. T or F?

Answer 8

True

Question 9

What is the gold std for GFR measurement? What is used instead?

Answer 9

Inulin;

CCG equation from creatinine

Question 10

What is the CCG equation?

Answer 10

CrCl = (140-age)xKG) / (72xScr) (0.85 if female)

Question 11

what weigt do you use if the pt is obese?

Answer 11

Wt > 120% of IBW use ABW

Question 12

If emaciated use what weight?

Answer 12

ABW, round Scr to 1

Question 13

if extensive 3rd spacing use what weight?

Answer 13

best estimate of dry weight

Question 14

What is the equation for calculating IBW?

Answer 14

Males: 50kg + 2.3(inches over 60)
Females: 45.5kg + 2.3(inches over 60)

Question 15

What is the adjusted body weight equation?

Answer 15

IBW + 0.4(TBW - IBW)

Question 16

For drugs that have a high fraction excreted unchanged in the urine, do we need to change the dose?

Answer 16

Potentially yes

Question 17

What is the peak and trough of Once Daily Dosing for Aminoglycosides?
What is the goals of therpay in terms of MIC or AUC for aminoglycosides?

Answer 17

Peaks: 20-30 mg/L
Trough: <0.5 mg/L

Peak should be 10x MIC
Maintain AUC of 70-100

Question 18

Does Once daily dosing confer less renal and ototoxicity? Why?

Answer 18

yes

1) large dose results in less uptake by renal and inner ear cells due to saturation
2) troughs low and frequently undetectable, thus decreasing exposure time

Question 19

Does once daily dosing show equal or improved efficacy with less nephrotoxicity and faster time to eradication of organisms?

Answer 19

Yes

Question 20

When should you draw levels for aminoglycosides?

Answer 20

At the Peak level and at a random level

Question 21

Is Vancomycin nephrotoxic and ototoxic?

Answer 21

yes and yes

Question 22

What is the goal of therapy for Vancomycin in terms of the trough?

Answer 22

Maintain trough levels 4-5x > MIC

Question 23

Drug removal during Hemodialysis occurs at molectular weight <____ and water solubility?

Answer 23

<500 MW and yes, water solubility

Question 24

After HD how much aminoglycosides (Tobra, gent) should you give to replace loss?

Answer 24

2mg/kg load; 1mg/kg after each HD

goal level after dose is a peak of 4-5 mg/L

Question 25

In a conventional HD (4hr HD) and High-flux HD (2hr HD) about what percentage of the drug is removed?

Answer 25

50%

Question 26

Renal Failure on metabolized drugs, what happens to these drugs?
Meperidine
Morphine
Propoxyphene

Answer 26

Meperidine – > Normeperidine –> seizures
Morphine –> M-6-glucuronide –> morphine induced nacrosis
Propoxyphene –> Norpropoxyphene –> CNS and Cardiac toxicities