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Health Services Research & Development

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2006 HSR&D National Meeting Abstract


1018 — Polypharmacy and Prescribing Quality in Elderly Veterans

Author List:
Steinman MA (San Francisco VAMC)
Landefeld CS (San Francisco VAMC)
Rosenthal GE (Iowa City VAMC)
Bertenthal D (San Francisco VAMC)
Sen S (San Francisco VAMC)
Kaboli PJ (Iowa City VAMC)

Objectives:
Measures of prescribing quality for elders often focus on the misuse and overuse of medications, particularly in the setting of polypharmacy. However, little is known about how the number of medications taken is associated with rates of medication underuse, or about the relative frequency of different kinds of prescribing problems.

Methods:
We assessed medication prescribing quality in a cohort of 196 veterans age 65 and older who were taking 5 or more medications. Inappropriate medication use was assessed by a combination of drugs-to-avoid criteria and subscales of the Medication Appropriateness Index that assess whether a drug is ineffective, not indicated, or therapeutically duplicative. Underuse was assessed by the Assessment of Underutilization of Medications instrument. Previous studies have demonstrated good interrater reliability of these instruments (kappa 0.59-0.83).

Results:
Mean age was 74.6 years, and patients used a mean of 8.1 medications (SD 2.5). Among 196 veterans, 128 (65%) were taking at least one inappropriate medication, and 125 (64%) were missing at least one potentially useful medication; 82 (42%) had both types of quality problems. In log-linear models, the number of inappropriately prescribed medications rose sharply with increasing total number of medications (beta-coefficient 1.68, 95% CI 1.23-2.12), from a mean of 0.4 inappropriate medications in patients taking 5-6 drugs to 1.9 inappropriate medications in patients taking 10 or more drugs. However, the frequency of medication underuse did not vary with changes in total number of medications taken, averaging 1 underused drug in patients taking few or many medications (beta-coefficient 0.27, 95% CI -.20-0.74). Overall, patients on fewer than 8 medications were more likely to be missing a useful drug than to be taking an inappropriate one.

Implications:
Inappropriate medication use is strongly associated with the total number of medications taken, while underuse is frequent and equally common in patients taking few vs. many medications.

Impacts:
In patients taking fewer numbers of medications, evaluation of potential undertreatment should be a priority, whereas patients taking many medications should have close attention paid both to undertreatment and to use of inappropriate drugs.


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