Public Policy

Renal Function Caveats

Use of increased numbers of medications and age-related decline in renal function make older patients more susceptible to adverse medication effects. Drug pharmacokinetics change, and it’s important to remember that drug metabolism is affected by a number of processes.

Renal elimination of drugs is based on nephron and renal tubule capacity, which decrease with age.1 Older individuals will not metabolize and excrete drugs as efficiently as younger, healthier individuals.

According to the Centers for Disease Control and Prevention (CDC), there are more than 36 million adults in the United States older than 65, and overall U.S. healthcare costs related to them are projected to increase 25% by 2030.2

The Cockroft-Gault Equation

Preventing health problems, preserving patient function, and preventing patient injury that can lead to or prolong patient hospitalizations will help contain these costs.

Quartarolo, et al., recently reported that although physicians noted the estimated glomerular filtration rate (GFR) in elderly hospitalized patients, they didn’t modify their prescribing.3 They also noted that drug dose changes in these hospitalized patients are important to prevent dosing errors and adverse reactions.

New Drugs

The FDA has approved a 300 mg Plavix tablet (clopidogrel) indicated for use as a loading dose in appropriate patients following hospital admission for acute coronary syndrome. A combination product of olmesartan and amlodipine, known as Azor, has been FDA approved as monotherapy or in combination with other treatments for hypertension.

SAFETY

Genetic Dosing Clues

A genetic test to identify which patients have genetic variants to metabolize warfarin has been used to more accurately predict initial individualized doses. This is one of the first steps toward personalized medicine using pharmacogenomics. Approximately one-third of patients metabolize warfarin differently than the rest of the population based on variants of VKORC1 and CYP2C9 genes. These genetic tests are being used to more accurately predict warfarin doses to decrease adverse events and improve patient outcomes.

Get to Know MEDMARX

Each year the United States Pharma­copeia (USP) analyzes medication errors submitted by facilities participating in its national medication error and adverse drug reactions (ADR) reporting program, MEDMARX. Data are compiled, summarized, and presented in an annual report. The report includes types of medication errors, causes, contributing factors, products, and actions taken.

The 2005 MEDMARX Report analyzes more than 11,000 perioperative medication error records submitted to MEDMARX over a seven-year period. The Joint Commission noted how difficult it is for facilities to achieve anticoagulation safety on a national scale. Of the 519 products involved in harmful errors in this report, heparin ranked third, warfarin sixth, and enoxaparin ninth. Of the 17 medication-related deaths reported to MEDMARX in 2005, four involved enoxaparin.

The 2008 Joint Commission Hospital Safety Goals include a new requirement (3E) titled “Reduce the likelihood of patient harm associated with the use of anticoagulation therapy.” All anticoagulants are included: low-molecular weight heparins, unfractionated heparin, warfarin, and others. Full-implementation is expected by Jan. 1, 2009.

One of the first requirements of the phase-in (due April 1) is for the hospital to assign oversight and coordination of developing, testing, and implementing 3E. One of the major implementation expectations is to have a defined anticoagulation management system for each patient receiving one of these agents. This will be another measure on which organizations will be scored during Joint Commission surveys.—MK

There are four major age-related pharmacokinetic parameters:

  • Usually decreased gastrointestinal absorption changes ;
  • Increases or decreases of a drug’s volume of distribution leading to increased blood drug levels and/or plasma-protein-binding changes;
  • Usually decreased clearance with increased drug half-life effect (hepatic metabolism changes); and/or
  • Decreased clearance (and in­creased half-life) of renally eliminated drugs.4,5
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