Suboptimal prescribing of primarily renally cleared medications for older VA nursing home (NH) patients

Hanlon JT, Wang X, Handler SM, Weisbord SD, Semla TP, Stone RA, Aspinall SL. Suboptimal prescribing of primarily renally cleared medications for older VA nursing home (NH) patients. Poster session presented at: American Geriatrics Society Annual Meeting; 2010 May 15; Orlando, FL.

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Purpose: Many medications with a high risk for adverse drug reactions are primarily renally cleared.The objectives of this study were to estimate the prevalence of suboptimal prescribing (use of contraindicated or greater than maximum daily dosage) of one or more primarily renally cleared medications based on two separate estimates of renal function and to identify factors associated with this form of suboptimal prescribing in olderVA nursing home (NH) patients. Methods: This longitudinal study included 3480 patients aged 65 years or older admitted between January 1, 2004 and June 30, 2005 for 90 days or more to one of 133VANHs.Using the Cockcroft-Gault (CG) and the Modification of Diet in Renal Disease (MDRD) equations, we estimated creatinine clearance and glomerular filtration rates for the 1304 patients (37.5%) who were taking any of 22 primarily renally cleared medications.We applied explicit guidelines (regarding both contraindications and dosing) to the prescribing of these medications. Multivariable logistic regression analyses were conducted to identify factors associated with suboptimal prescribing based on the CG equation. Results: Most patients were male (97.8%), 16.8% were aged 85+, and 20.8% were obese (BMI > 30). Most patients had multiple comorbidities (mean Charlson comorbidity index = 3.1;SD = 2.2) with a median estimated creatinine clearance of 67 mls/minute (CG equation). Using the CGequation,11.9% of patients had evidence of suboptimal prescribing for at least 1 renally cleared medications, while considerably fewer patients (5.9%) had such evidence based on the MDRD equation. The most common suboptimally prescribed medications were ranitidine, glyburide, gabapentin and nitrofurantoin. Factors associated with suboptimal prescribing were age 85+ (AOR 4.2,95% CI 2.4-7.3), obesity (AOR 0.3, 95% CI 0.1-0.5) and having multiple comorbidities (AOR 1.1 for each unit increase in the Charlson comorbidity index,95% CI 1.0-1.2). Conclusions: Suboptimal prescribing of renally cleared medications is common in older VA nursing home patients. Future intervention studies that also examine the impact on health outcomes are needed to address this issue.