Nephrology: 3. Safe drug prescribing for patients with renal insufficiency.

T he number of people with end-stage renal disease (ESRD) in Canada is increasing. In 1999, 142 individuals per million population were receiving renal replacement therapy, which is an increase from 83 per million population in 1990. 1 The leading cause of ESRD is diabetes (30%) followed by renal vascular disease, including hypertension (20%). Over the past decade, the number of older Canadians (aged ≥ 65 years) with ESRD has more than doubled. 1 Unfortunately, the number of people who have some degree of renal insufficiency, but have yet to need renal replacement therapy, is not fully known. Those groups at risk for developing renal impairment include individuals with diabetes, elderly people, those with hyper-tension, certain ethnic groups (i.e., Aboriginal people) and individuals with atherosclerotic disease elsewhere, autoim-mune and genetic diseases, or a family history of renal disease. The third National Health and Nutrition Examination Survey (NHANES III) estimated that 14.7 million people in the United States had renal insufficiency. 2 Based on these data, one could estimate that there are about 1.5 million Canadians with renal insufficiency. On average, patients with renal insufficiency are taking at least 7 different medications to manage not only their underlying disease (such as diabetes) but also the symptoms related to their renal impairment (i.e., problems with mineral metabolism, anemia). 3,4 The frequency of adverse drug reactions increases with the number of medications used, the degree of renal dysfunction, the age of the patient and the number of comorbid conditions. 5,6 As the kidney is a major organ of drug elimination, some knowledge of basic pharmacologic principles and a systematic approach to patients with renal insufficiency are necessary to ensure safe and effective patient care. All patients who are at risk for renal insufficiency should have their renal function assessed as part of their periodic health examination. At the very least, serum creatinine should be tested, recognizing that measuring serum creati-nine alone will fail to diagnose abnormal function in 35% of people aged 40–49 years and 92% of people more than 70 years old. 7 A more accurate reflection of renal function is creatinine clearance. Guidelines for the investigation of newly diagnosed renal insufficiency exist elsewhere. 8 For patients with established renal insufficiency, a thorough history-taking, physical examination and certain basic laboratory tests are essential to identify individuals who may require adjustments to their medication. The patient's history should include a record of current …