Renal Pharm Flashcards
Describe GFR
- gold standard measurement of kidney function
- requires exogenous substance as a marker
- eGFR used for staging, transplant list, medication dosing
What does a declined GFR indicate
- disease progression or reversible insult (decreased renal perfusion)
(correlation between loss of nephron function and GFR decrease is not exact)
What substances are typically used as a marker for GFR
- insulin
- sinistrin
- lothalamate
- lohexol
- radioisotopes
- Creatinine
Describe how GFR is estimated with creatinine
- 24 hr urine collection (CrCl) or blood draw (SCr)
- can’t be reliably used alone because serum levels don’t rise until significant destruction of nephrons occurs
- levels vary greatly over a day
- today’s SCr reflects yesterdays renal function
- can’t account for tubular secretion
What things can affect sCr
- extremes in body weight & muscle mass (high)
- protein consumption (high)
- malnutrition (low)
- skeletal muscle disease
- pregnancy
- unstable renal function
- Cr supplements
- bactrim (TMP-SMX) (temporary)
At what percent of renal elimination will a drug require renal dose adjustment in CKD
> 30%
Describe how CKD can affect pharmacokinetics
- delayed gastric motility with DMII, n/v
- variable fluid status & less protein for binding
- accumulation of metabolites which may impact metabolism
What are the two main goals of renal dosing regimens
- maintain similar/normal peak/trough
- maintain average steady-state concentration
when would you want to maintain a similar/peak trough through renal dosing
- with concentration-dependent antimicrobials (aminoglycosides)
- meds with a narrow therapeutic index/high toxicity risk (digoxin, phenytoin)
Ex.
Usual: amikacin 525mg q8h
adjusted: amikacin 525mg q24-72h
Result: similar peaks & troughs
when would you want to maintain a similar steady-state concentration through renal dosing
- meds without established peak/troughs (BP meds
- time dependent antimicrobials (beta-lactams)
Ex.
Lisinopril
- normal GFR: no dose adjustment
- reduced GFR: give 50-70% of usual dose
- severely reduced GFR: give 25-50% usual dose
Result: similar steady state concentration
How do you maintain a similar peak/trough in renal dosing?
Extend the dosing interval
How do you maintain a similar steady state in renal dosing?
Decrease the dose
What are medication considerations if a patient is receiving hemodialysis
- give highly dialyzable meds (low molecular weight, minimal protein binding, hydrophilic) right after dialysis
- avoid anti-HTN & vasoactive drugs in the hours before dialysis (or skip that day)
Describe the MOA and Effect of ACE/ARBs for proteinuria
MOA: vasodilate efferent arteriole by blocking angiotensin II & reducing glomerular pressure
Effect:
- decrease baseline GFR
- decrease proteinuria
- slow disease progression
Pearls: Risk of hyperkalemia, start with low doses in CKD
List some drugs that impair tubular secretion
- SMX-TMP
- dronedarone
- cimetidine
- dolutegravir & cobicistat
- tyrosine kinase inhibs (imatinab, sunitinib, crizotinib)
