Chronic kidney disease (CKD) is a spectrum of conditions characterized by a progressive loss of kidney function. Thirty million Americans have some form of CKD, and millions more run the risk of developing it. Protecting and preserving kidney function can be an undertaking, as many medications are either cleared by the kidneys or alter kidney function. In dialysis patients, some drugs may dialyze out if administered prior to dialysis. But successfully managing this patient population transcends the intricacies of patient individuality and pharmacokinetics and must acknowledge that patients lack of awareness regarding the full spectrum of the condition.
“Kidney disease is very common, and often people who have it don’t necessarily know they have it because they don’t have symptoms until it’s quite advanced. In fact, many people don’t feel bad until they approach end-stage kidney disease,” says Kevin Erickson, MD, assistant professor medicine at Baylor College of Medicine.
Impaired kidney function affects other areas of the body, making monitoring exceedingly important. The kidneys play an important role in maintaining homeostasis in the body by regulating the extracellular fluid volume, one of the body’s natural buffering systems, and the body’s internal pH; governing ion concentrations; equilibrating the body’s osmolarity; excreting waste and other unwanted substances; and producing and activating hormones, including renin and erythropoietin. Anything that impairs kidney function can compromise the kidney’s ability to execute these critical tasks.
Choosing Medications and Doses
Different stages of kidney damage are defined by the rate at which the glomeruli of the kidney filter blood, the glomerular filtration rate (GFR). A GFR of 90 ml/min is classified as a stage 1 kidney disease with normal function while lower GFR values correspond to worsening kidney function. The most severe form of kidney disease—kidney failure—results in severe or near-complete loss of kidney function. According to Erickson, kidney function changes over time, so medications—especially those cleared by the kidneys—may require adjustments if taken for long periods.
From a pharmacological standpoint, the kidneys are one of the mechanisms by which the body clear drugs, so as kidney function declines, some drugs will accumulate within the body. Dose adjustments may involve decreasing the dose and dosing frequency for medications that are cleared renally. For example, an antibiotic typically dosed twice a day might need to be administered at half the dose and only once a day in a patient with reduced kidney function. Additionally, certain medications can cause additional kidney damage in some patients who are already renally compromised.
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