91 CLINICAL DIABETES • Volume 27, Number 2, 2009 C A S E S T U D I E S Case Series: Premixed Insulin Dosing in Actual Practice: Two-Thirds in AM, One-Third in PM, or Half and Half? Anuj Bhargava, MD, MBA, CDE, FACP, FACE, June Felice Johnson, BS, PharmD, FASHP, BC-ADM , and Joseph P. Weir, PhD, FACSM, FNSCA Initiation of insulin in type 2 diabetic patients failing to meet glycemic targets may include addition of either intermediate- or long-acting basal insulin or a biphasic premixed insulin that incorporates both basal and bolus insulins. Dual-acting basal/bolus insulin preparations are administered before meals to improve postprandial glucose levels and provide sustained glucose control throughout the dosing interval. Premixed insulins increase the conve- nience and acceptability of insulin use by type 2 diabetic patients who are not willing to take on or are not yet candidates for intensive basal/bolus insulin therapy. 1,2 The conventional initial approach to dosing premixed insulins (bipha- sic insulin aspart 70/30, biphasic insulin lispro 75/25, or regular/NPH 70/30) still cited in medical texts and used in general practice is to prescribe a ratio of two-thirds of the total daily insulin dose in the morn- ing before breakfast and one-third in the evening before dinner. 3–5 Health care providers in nonspecialty set- tings may be less likely to use ratios other than two-thirds/one-third because of concerns regarding the safety and effectiveness of a regimen that does not follow this conven- tional approach. Yet, it is dificult to ind practical evidence to guide pro- viders in using a different premixed insulin regimen. After an extensive literature search of published clinical trials of premixed insulins, the authors were unable to reliably determine the ratios used in studies of type 2 diabetic patients in which premixed insulins were compared to each other or compared to basal or bolus insulins alone. No studies examined the actual prescribing patterns of the premixed insulins when used in a realistic clinical specialty practice setting in which endocrinologists use more treat-to-target approaches for rapid dose titration of insulin. This retrospective, observational, descriptive study was designed to examine the use of premixed insulins in a community-based endocrinol- ogy practice and to analyze the ratio, hereafter referred to as the “dosing ratio,” for morning and evening doses of premixed insulin. The pri- mary objective was to determine the dosing ratio of evening doses to total daily doses (TDDs) of insulin and compare it to the “standard” dosing ratio of 0.33. Secondary objectives were to determine the correlation between dosing ratios and A1C and between TDD and A1C. PATIENTS AND METHODS Study subjects. The study sample was selected from a population of adult patients (> 18 years of age) who received their diabetes care from a specialty endocrinology private group practice ofice and who were cur- rently prescribed premixed insulins. During the data collection period, the practice employed ive endocrinolo- gists, three mid-level practitioners, two diabetes educators, and adequate nursing and support staff. It currently manages > 5,000 patients with diabe- tes, about two-thirds of whom have type 2 diabetes. Patient records were included for review if the patients were fol- lowed in the endocrinology practice regularly for diabetes management, received any type of premixed insulin, and had been receiving premixed insulin twice daily for at least 3 months. Patient records were excluded from the study if the patients received only once-daily dosing of premixed insulin, received premixed insulin three times daily, administered premixed insulin for less than 3 months, or had no recorded A1C during the past year from the date of the electronic medi- cal record (EMR) review. Study procedures. The study used a retrospective, observational, descriptive design. All data were extracted from the EMR using an inquiry of the patient database applying the criteria listed above. Patient data were collected for the 1-year period before the date of the EMR review. The study was approved by the Mercy Medical Center Institutional Review Committee and Des Moines University Institutional Review Board. Data were collected during a 2-week period from the last week of November to the irst week of December 2006. Information gathered included age, sex, type of diabetes, duration of diabetes, weight, BMI, last two