Drug Dosing in the Elderly Patients with Chronic Kidney Disease
Section snippets
Pharmacokinetics
Pharmacokinetics defines and analyzes the time course of the drug in the body. Pharmacokinetic properties are altered in chronic kidney disease and in the natural aging process. These include bioavailability, volume of distribution (Vd), protein binding, and biotransformation.
Drug metabolism
Most drugs are metabolized to more soluble compounds, which are then removed from the circulation. Drug metabolites are pharmacologically inactive; however, several drugs have active metabolites that are excreted through the kidney. Patients with chronic kidney disease are at a higher risk of drug accumulation and toxicities in this setting. For example, procainamide has an active metabolite, N-acetyl procainamide (NAPA). NAPA has pro-arrhythmic properties and is excreted by the kidneys.35
There
Approach to dosage adjustment in older adults
Most guidelines recommend a small drug dose and dosing adjustments in older adults with or without chronic kidney disease. Age-related changes in organ function may alter the renal elimination rate of the drugs. The following recommendations provide a simple approach for health care providers, and attempt to reduce the risk of drug toxicity and improve pharmacotherapeutic efficacy.42 At any point of care, patient-specific risk factors such as comorbidity, drug interactions and health care
Dialysis and drug dosing
In 2005, 1 in 1000 people received renal replacement therapy in the United States. Today it is estimated that more than 350,000 patients are on dialysis. There are a limited number of published studies on drug pharmacokinetics and clearance in the geriatric population that who undergoes various dialytic modalities. Therefore, most of the data are extrapolated from the general population on dialysis. Hemodynamically unstable patients also require continuous arteriovenous hemofiltration (CAVH),
Dosing tables
Tables 2–16 in the Appendix present key information required for prescribing drugs in patients with chronic kidney disease. These tables should be used with caution and the overall situation of each patient should be fully considered. For some drugs, adjustment is an interval extension (I), whereby the dosage stays the same as an adult without kidney disease. On the other hand, if the dose reduction method (D) is recommended, the adjustment refers to the percentage of the dose given to a
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