Drug use in renal impairment
 
Drugs that are predominantly excreted unchanged in the urine may require a dose adjustment in renal impairment. This is particularly important for drugs with a narrow therapeutic index.
 
Dose adjustment in renal impairment
 

1.

Determine the fraction of the drug that is excreted unchanged by the kidney (fu)
If fu <0.5, no need to continue as dose adjustment not required. (See drug data below)
 
2. Calculate the patient's renal function, i.e. creatinine clearance (CrCl).
 
  Lean body weight (kg) males = 50kg + 0.9kg for each cm > 150cm in height
  Lean body weight (kg) females = 45kg + 0.9kg for each cm > 150cm in height
  (Christchurch hospitals use μmol/L, reference range: 50-110μmol/L)
 
3. For drugs with fu ≥ 0.9, calculate dose-rate (DR) as follows:
 
  NB. Normal dose rate (DR) = dose rate for a patient with normal renal function
 
4. For drugs with fu < 0.9, calculate dose-rate (DR) as follows:
 
 

Drugs for which dose adjustment should be considered in patients with renal dysfunction

Low therapeutic index drugs

 - Dose-adjustment essential

 

High therapeutic index drugs

 - Dose-adjustment may decrease side effects

  
Drug fu Drug fu
Aminoglycosides   b-blockers  
  gentamicin 0.9   atenolol 0.9
  netimicin 0.9   nadolol 0.8
  tobramycin 0.9   sotalol 0.9
       
Cytotoxics  

Penicillins

  
  carboplatin  0.9   All ≥ 0.7
  cisplatin 0.9      
  flucytosine  0.9 Cephalosporins  
  methotrexate 0.9~0.5**   All  ≥ 0.7
        (except ceftriaxone - 0.5)  
ACE inhibitors      
  captopril 0.5 H2-Antagonists  
  cilazapril* (cilazaprilat) 0.9   cimetidine 0.7
  enalapril* (enalaprilat) 0.9   famotidine 0.7
  lisinopril 0.9   ranitidine 0.7
  quinapril* (quinaprilat) 0.9    
      Other  
Other     aciclovir 0.8
  allopurinol* (oxypurinol) 0.8   amantadine 0.9
  candesartan 0.6   baclofen 0.8
  dalteparin 0.7   cetirizine  0.7
  digoxin 0.8   fluconazole 0.8
  enoxaparin  0.7   ganciclovir 0.8
  gabapentin  0.8   imipenem 0.7
  lamivudine 0.8   meropenem  0.7
  lithium  1.0   oseltamivir* (oseltamivir carboxylate) 0.9
  metformin  0.9   pethidine* (norpethidine) 0.9
  teicoplanin 1.0   trimethoprim  0.7
  tranexamic acid  0.9    
  vancomycin 0.9    
  vigabatrin 0.6    

* metabolite with high fu; ** less with higher doses. 

 

Page Last Updated: 26/09/08

Clinical Pharmacology Department : Christchurch Hospital : Private Bag 4710 : Christchurch : 8140 : NZ

Phone 0800 DRUGINFO (378 446) : email druginfo[AT]cdhb.govt.nz