Drug Use Evaluation of Sitagliptin Dosing by Pharmacist Versus Nonpharmacist Clinicians in an Internal Medicine Department of a Private Physician-Owned Multispecialty Clinic

BACKGROUND: Sitagliptin is recommended for initial and maintenance dosing at 100 mg daily. Downward dose adjustment is recommended in patients with moderate or severe renal insufficiency. OBJECTIVES: To determine the prevalence of the potentially inappropriate initial dosing of sitagliptin based on estimated glomerular filtration rate (GFR) at baseline for pharmacist versus nonpharmacist prescribers in an internal medicine department of a private physician-owned multispecialty clinic that included a pharmacist-managed diabetes program. METHODS: This was a retrospective cross-sectional cohort analysis using data from an electronic medical record database of a private physician owned multispecialty clinic that included a pharmacist-managed diabetes program. For patients prescribed sitagliptin between October 17, 2006, and June 5, 2008, the variables of interest were (a) the initial sitagliptin dose; (b) the GFR, calculated for each patient using the 4-point Modification of Dosing in Renal Disease (MDRD) formula at the time of initiation of sitagliptin; and (c) whether the clinician initiating the dose was a pharmacist or nonpharmacist (i.e., internal medicine physician, nurse practitioner, or physician assistant). RESULTS: Of the 290 patients prescribed sitagliptin for the first time between October 17, 2006, and June 5, 2008, 35 (12.1%) received a potentially inappropriate initial dose according to product labeling regarding renal function; 21 were over-dosed and 14 were under-dosed. Potentially inappropriate dosing occurred in 1 of 158 patients (0.6%) who had initial dosing prescribed by a pharmacist compared with 34 of 132 patients (25.8%) for nonpharmacists (P less than 0.001, Fisher's exact test). CONCLUSIONS: Potentially inappropriate initial dosing of sitagliptin based on assessment of renal function was more likely to occur with nonpharmacist prescribers than with a pharmacist prescriber.