Drug Dosing in Chronic Kidney Disease Flashcards Preview

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Flashcards in Drug Dosing in Chronic Kidney Disease Deck (34)
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What is the definintion of glomular filtration rate?

Why is it important?

the volume of fluid filtered from the renal glomerular capillaries into the Bowman’s capsule per unit time.

Determines renal function


What should we remember about Sr Cr levels?

1. dont use it as the true marker of kidney function
2. slight bump in creatinine in an acute setting is a big problem! Red flag


What specific sign would clue us in to kidney disease?

Be thinking about kidney disease when they are HTN. abnormalitites on the UA with this would help.


What is GFR estimated by?

Estimated by creatinine clearance (CrCl)


What are two ways to acquire CrCl?

1. The least common is through direct collection – measurement of the creatinine in a twenty four hour sample of urine

2. The more common and practical way is to calculate creatinine clearance using serum creatinine (SCr)
Why is this? Easy to get a simple blood test


What’s the problem with a 24 hour collection?

1. Compliance issues
2. Requires proper collection technique for accuracy


What is creatinine?

The decomposition product of the metabolism of phosphocreatine, a source of energy for muscle contraction.

meat that we eat too. (sr cr will be higher)


The higher the CrCl the 1.______ the kidney function, the higher the serum SCr the 2.______ the kidney function

1. better
2. worse


What is a normal SCr?

About 0.6-1.3mg/dL (depends on the lab)


The Cockcroft-Gault Equation?

How do we calculate ideal body weight?

What would happen if…
You increased the age?

Increased the weight?

CrCl (male) = (140-age) x weight (kg)/72 x SCr (mg/dL)
CrCl (female) = 0.85 x male CrCl

Male 50.0 kg + 2.3kg per inch over 5 feet
Female 45.5kg + 2.3kg per inch over 5 feet

CrCl would be lower (older=lower)
CrCl would be higher (accounting for more muscle mass-ideal body weight)


In pts that are over 18 and have a SCr of less than 1 what number should we use?

How is CrCl expressed?




Who should we always check GFR on? 2

65 and older
SrCr less than 1.5


Causes of Chronic Kidney Disease
Nephrotoxic agents:

2. Aminoglycosides
3. Heavy metals (lead, gold compounds, mercury)
4. Radiocontrast (iodide compounds)
5. Ethylene glycol (antifreeze)- occurs 24-72 hours post injection. direct cytotoxic affect.


1. How do NSAIDS affect kidney function?

2. Why would we not want to biopsy a kidney issue caused by radiocontrast?

1. blocks prostagladin activity, kidney vessels constrict and limit blood blood

2. dont biopsy them because it usually goes away after/refuses right away


How would uremia affect the plasma protein binding of a drug?

Uremia may inhibit or enhance protein binding, therefore more active drug is in the system.


Elimination-renal clearance:
1. Dependent on the processes of _______ _______ and ______ _______
2. Some drugs are converted to _________ that maintain pharmacologic activity when they accumulate in a patient with renal dysfunction.

3. When renal disease reduces _______ ________, the kidney’s ability to eliminate drugs declines in proportion to the decline in GFR.

4. What happens to the drugs that are usually filtered in kidney failure and what does this cause?

1. glomerular filtration and tubule transport

2. metabolites

3. nephron number

4. Drugs usually filtered and excreted accumulate, which produces a high prevalence of adverse reactions.


1. Some drugs have toxic effects with high peak concentrations. Whats an example?

2. Other drugs have toxic effects with prolonged trough concentrations. Whats an example?

1. Imipenem can induce seizures at high concentrations

2. Aminoglycosides can cause nephrotoxicity (adding insult to injury) or ototoxicity with sustained trough levels above 2mcg/mL


Drug Dosing in Chronic Kidney Disease: Two methods of dose adjustment?

1. Smaller dose
2. Longer interval between doses


1. If GFR is less than ___ ml per min they will not eliminate that drug.
2. Be careful with drugs with pretty long half lives because why?

1. 50

2. it will be unpredictable for how long they will stick around or what the effect will be


1. WHat is the purpose of a loading dose?

2. How is this affected in renal failure?

1. Are intended to generate a therapeutic steady-state drug level within a short period.

2. Despite renal failure, the loading dose is usually not different from normal.


How long after should we check digitalis after we've given it for toxicity?

check a dig 6-12 hours after you’ve given drug. then lower their maintenance dose if you’ve given too much loading dose


1. WHat is the purpose of a maintenance dose?

2. In the absence of a loading dose, maintenance doses will achieve 90% of their steady-state level in ___ half lives

1. Are used to sustain a therapeutic level when they are administered subsequent to a loading dose.

2. 3.3


What are the maintenance methods for dealing with kidney failure pts?

1. Dosage reduction method

2. Interval extension method


Describe each of the following methods of maintenance dosing in pts with renal failure and the benefit of each?

- Reduce amount of each dose, but interval time remains the same
- Sustains a more constant blood level

- Q 24 hours instead of q 12 hours, dose remains the same
- This method is practical for dugs with long half lives.


What about patients who are receiving dialysis, how and when should we dose their meds?

1. Supplemental doses may be required
2. Dose can be given after dialysis

pain meds and blood pressure meds- usually give after dialysis. make sure to talk to the nephrologists


Specific dosing guidelines based on patients renal function

Unless otherwise noted, one can assume that dose modification is not necessary for patients with GFR’s >50.


Drug Dosing in Chronic Kidney Disease: monitoring is done how?

What drugs should we monitor? 6

Monitoring drugs by serum level
Wide variations in elimination in CKD (you have to look it up!)

1. Aminoglycosides
2. Digoxin (MAKE sure you know what time they took it)
3. Antiarrhythmic drugs
4. Vancomycin
5. Lithium
6. Anticonvulsants


WHat are the Antiarrhythmic drugs we should be monitoring in CKD pts?

What are the anticonvulsants we should monitor?

1. disopyramide
2. flecainide (if not at therapuetic levels it can cause arrythmias)
3. lidocaine
4. procainamide
5. quinidine
6. tocainide

1. Carbamazepine
2. Phenobarbital
3. Phenytoin
4. Valproic Acid


Drug supplementation with dialysis:
1. How should we deal with drugs that are dialyzed off?
2. not dialyzed off?

1. Most or all of drug is removed from blood stream during dialysis
Give dose after dialysis

2. no supplemental dose needed


Some antibiotic pearls to remember for CKD:
Examples of a few drugs where no dosage adjustment is required with chronic kidney disease:

1. Azithromycin (Zithromax)- protein synthesis inhibitor
2. Ceftriaxone (Rocephin)- beta lactam- interferes with cell wall synthesis.
3. Moxifloxacin (Avelox)- tendon rupture.
4. Doxycycline (Vibramycin)- tetracycline group. no prgnant or kids under 8