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Renal Function and Drug Dosage
- Most drugs (or their metabolites) used in hospital practice are excreted in whole or in part through the kidneys.
- The dose of most drugs should be modified in patients with renal insufficiency according to the fraction excreted unchanged (fu) and the creatinine clearance. This is particularly important for drugs such as low molecular weight heparin, dabigatran, the aminoglycosides, cephalosporins, ranitidine, digoxin, ACE inhibitors and some beta-blockers. Drugs which are metabolized extensively do not usually require dose adjustment in renal insufficiency unless an active metabolite or toxic metabolite is excreted through the kidneys. The fu of commonly used drugs is available in the Preferred Medicines List.
- Some drugs should be avoided completely or used with great care in the presence of renal insufficiency. These include - tetracyclines (except doxycycline), co-trimoxazole, nitrofurantoin, nalidixic acid, K-sparing diuretics (spironolactone, amiloride, triamterene), fibrates and NSAIDs (including COX-2 inhibitors).
ACE inhibitors are used widely for the management of hypertension, chronic kidney disease and cardiac failure. However, patients may develop AKI due to an excessive dosage related to the renal clearance of the drug or in the presence of renovascular disease. This is more likely to occur if the patients are also taking a diuretic or NSAID, or are dehydrated from any cause. ACE inhibitors should be stopped before surgery and should not generally be used in combination with potassium-sparing diuretics, potassium supplements, or NSAIDs. Refer to the recommendations for the doses of quinapril and enalapril in renal impairment.
Topic Code: 2739