Renal dosing v4 feb 08.pub

Clinical Update
Renal Function in the Elderly
An estimated 1.9 million Canadians have chronic kidney disease.1 Renal Adjustments
impairment is more common in the elderly, and rising steadily, with the for Patients
number of Canadian seniors developing kidney failure more than doubling over the past 10 years.2 Approximately 10% of community-dwelling adults, and up with Renal
to 20% in those aged 80 years or older have renal impairment.3,4 It is especially Insufficiency
prevalent in long-term care settings where 44% of men and 70% of women have renal impairment.5 Although age-related decreases in renal function are well described in the literature,6 renal impairment is frequently unrecognized in Jane Jurcic Vrataric
Did you know?
BSc(Pharm)
• The glomerular filtration rate (GFR) decreases by
about 1 mL/min for each year over the age of 40.6
Reviewed by:
• The three leading causes of kidney failure in new
patients are: diabetes (33%), renal vascular disease,
including hypertension (19%), and glomerulonephritis
(13%).2
Alexandra Papaioannou BScN, MD, MSc, FRCPC Drug Issues with Renal Impairment
Many drugs are cleared by renal excretion, and the clearance of these drugs and their metabolites is lowered in the presence of reduced kidney function. Some drugs require dosage adjustments according to kidney function. Other drugs may be completely contraindicated in the presence of impaired kidney function. Failure to adjust the dosage of medications for patients' renal function is an important contributor to adverse drug events, and may cause www.tippsnetwork.ca “Clinical Updates” section subclinical issues as well. Previous studies have identified that physicians often do not adjust medications in individuals with renal impairment, particularly amongst elderly people.9,10 Accurate drug dosing and appropriate drug selection are necessary to reduce the frequency of adverse drug events and to improve the pharmacological management of patients’ Research Grant 2004-05 and the CIHR New Emerging Team Grant (NET-54028) Inside .
Dosage Adjustments for Selected Drugs …. Page 2 and 3
Identifying and Defining Renal Impairment … Page 4
Measuring Renal Impairment … Page 4
Dosage Adjustments for Selected Drugs11,12*
Usual Dose
Renally Adjusted Dose
Comments
(Based on CrCl ml/min)
CrCl > 50
CrCl 10 - 50
CrCl < 10
interstitial nephritis, exfoliative dermatitis. including GI (nausea, abdominal pain), CNS (headache, seizure), MSK (myalgia, arthralgia) due to accumulation. 25-75% q36h 10-25% q48h Increased risk of digitalis toxicity and uremic GI symptoms. Clearance decreased by amiodarone, spironolactone, quinidine, verapamil. Hypokalemia, hypomagnesemia enhance toxicity. Folic acid antagonist. Urolithiais. Crysalluria in acid urine. reported in moderate and severe renal insufficiency. reaction (active metabolite 50% excreted via kidney). Effective at low CrCl in combination with loop diuretic. including GI (nausea, abdominal pain), CNS (headache, seizure), MSK (myalgia, arthralgia) due to accumulation. symptoms of lithium toxicity at toxic serum levels. Renal adverse effects reported. Toxicity enhanced by volume depletion, NSAIDs, and diuretics. * 11 (The Renal Drug Book Online available at http://www.kdp-baptist.louisville.edu/renalbook/ ) was the reference for all drugs except: alendronate, risedronate, milk of magnesia and tolteridine. 12 (Geriatric Dosage Handbook) was the reference for the aforementioned drugs. Dosage Adjustments for Selected Drugs11,12*
Usual Dose
Renally Adjusted Dose
Comments
(Based on CrCl ml/min)
CrCl > 50
CrCl 10 - 50
CrCl < 10
CrCl < 30, especially in diabetes. Gynecomastia, hyperchloremic acidosis. elderly and by 30-35% in patients with renal dysfunction. * 11 (The Renal Drug Book Online, available at http://www.kdp-baptist.louisville.edu/renalbook/ ) was the reference for all drugs except: alendronate, risedronate, milk of magnesia and tolteridine. 12 (Geriatric Dosage Handbook) was the reference for the aforementioned drugs. Identifying and Defining Renal Impairment
The presence of chronic kidney disease is established based on the presence of kidney damage and the level of kidney function. Calculated creatinine clearance (CrCl) is used as an indirect estimation of kidney function, or glomerular filtration rate (GFR), to classify the severity of kidney damage. Chronic kidney disease is defined as either kidney damage or CrCl < 60 mL/min/1.73m2 for > 3 months.13 Kidney damage is defined as pathologic abnormalities or markers of damage, including abnormalities in blood or urine test or imaging studies.13 Among individuals with chronic kidney disease, the stage is defined by the level of CrCl, with higher stages representing lower CrCl levels. Table 1: Stages of Chronic Kidney Disease13 Kidney damage with normal or increased CrCl Measuring Renal Impairment
Estimates of creatinine clearance are the best overall indices of the level of kidney function. Equations to predict creatinine clearance from serum creatinine have been tested in a large number of studies and have been shown to give more valid estimates of kidney function than serum creatinine alone in patients of advanced age and decreasing muscle mass.5,7,8 The most frequently used equation for estimating kidney function in adults is the Cockcroft-Gault equation.14,15 Cockcroft-Gault formula for estimating creatinine clearance in mL/min based on serum creatinine †
140 - age (y) x weight (kg)
140 - age (y) x weight (kg) x 0.85
serum creatinine (µmol/L) x 0.8
serum creatinine (µmol/L) x 0.8
Calculators

To calculate CrCl on the internet, try:
• http://www.kidney.org/professionals/kdoqi/gfr.cfm
To download a calculator to your PDA, go to Epocrates:
• http://www2.epocrates.com/products/medtools/
† A correction factor is available for black patients

Source: http://osteoporosislongtermcare.ca/2011/PDFs/TIPPS-CLINICAL-UPDATE-RENAL2006.pdf