Pharmacy & Therapeutics - September 2008 - (Page 540)

Copays and Oral Antidiabetic Drugs Table 5 Time to Treatment Failure: Analysis by Drug Class Increased Likelihood of OAD Treatment Failure for Every $10 Increase in Copay 26.0% 20.5% 27.8% 10.4% 19.5% 95% Confidence Interval 22.3%–29.8% 17.1%–24.1% 22.2%–33.8% 8.4%–12.5% 13.0%–26.4% CONCLUSION In our study, higher drug copayments were associated with increased treatment failure and lower adherence to therapy, although increased adherence to therapy was associated with improved HbA1c levels. Health plans increase member cost sharing with the goal of saving expenditures. However, the impact on treatment persistence for chronic conditions will require ongoing evaluation. Negative consequences potentially associated with increased patient cost sharing should be con sidered in patients with type-2 diabetes. Drug Class All OADs Biguanides Sulfonylureas TZDs Other OAD = oral antidiabetic drug; TZDs = thiazolidinediones. each increase in copay category, patients in all therapy groups were more likely to experience treatment failure. This finding suggests that the effect is not one of a branded drug versus a generic agent; rather, it relates to the copayment level, irrespective of which OAD was received. As observed from the multivariate analysis, higher copays were also associated with poorer adherence to medication regimens. Cole et al., using a methodology similar to the one we used in our study, evaluated the effect of copays on adherence to angiotensin-converting enzyme (ACE)–inhibitors and beta blockers in patients with chronic heart failure. Their results also showed a small but significant association between copays and the MPR.14 As in the study of chronic heart failure, our model had a low r-squared value, which explains only 6% of the variation in MPR. Although we adjusted for many demographic and clinical characteristics, the use of claims data did not allow the capture of several factors (e.g., patient income, ethnicity, access to diabetes education, and choice of physician)24,25 that might affect adherence. In our study, a 10% increase in the MPR was associated with an absolute decrease of 0.12% in HbA1c levels. Our results agreed with those of Schectman et al., whose multivariate analyses demonstrated 0.16% lower HbA1c concentrations for each 10% increase in adherence. 8 The Schectman study involved an indigent population, whereas our study enrolled a commercially insured population. REFERENCES 1. National Institute of Diabetes and Digestive and Kidney Diseases. National Diabetes Statistics fact sheet: General information and national estimates on diabetes in the United States, 2005. Bethesda, MD, U.S. Department of Health and Human Services, National Institutes of Health, 2005. 2. Hogan P, Dall T, Nikolov P. Economic costs of diabetes in the U.S. in 2002. Diabetes Care 2003;26:917–932. 3. American Diabetes Association. Standards of medical care in diabetes—2006. Diabetes Care 2006(29 Suppl 1):S4–S42. 4. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). UK Prospective Diabetes Study Group. Lancet 1998;352:837–853. 5. Cramer JA. A systematic review of adherence with medications for diabetes. Diabetes Care 2004;27:1218–1224. 6. Dailey G, Kim MS, Lian JF. Patient compliance and persistence with antihyperglycemic drug regimens: Evaluation of a Medicaid patient population with type 2 diabetes mellitus. Clin Ther 2001; 23:1311–1320. 7. Gilmer TP, O’Connor PJ, Manning WG, et al. The cost to health plans of poor glycemic control. Diabetes Care 1997;20:1847–1853. 8. Schectman JM, Nadkarni MM, Voss JD. The association between diabetes metabolic control and drug adherence in an indigent population. Diabetes Care 2002;25:1015–1021. 9. Shetty S, Secnik K, Oglesby AK. Relationship of glycemic control to total diabetes-related costs for managed care health plan members with type 2 diabetes. J Manag Care Pharm 2005;11:559–564. 10. Testa MA, Simonson DC. Health economic benefits and quality of life during improved glycemic control in patients with type 2 diabetes mellitus: A randomized, controlled, double-blind trial. JAMA 1998;280:1490–1496. 11. Balkrishnan R, Rajagopalan R, Camacho FT, et al. Predictors of medication adherence and associated health care costs in an older population with type 2 diabetes mellitus: A longitudinal cohort study. Clin Ther 2003;25:2958–2971. 12. Lau DT, Nau DP. Oral antihyperglycemic medication non adherence and subsequent hospitalization among individuals with type 2 diabetes. Diabetes Care 2004;27:2149–2153. 13. Sokol MC, McGuigan KA, Verbrugge RR, et al. Impact of medication adherence on hospitalization risk and healthcare cost. Med Care 2005;43:521–530. 14. Cole JA, Norman H, Weatherby LB, et al. Drug copayment and adherence in chronic heart failure: Effect on cost and outcomes. Pharmacotherapy 2006;26:1157–1164. 15. Schultz JS, O’Donnell JC, McDonough KL, et al. Determinants of compliance with statin therapy and low-density lipoprotein cholesterol goal attainment in a managed care population. Am J Manag Care 2005;11:306–312. 16. Shrank WH, Hoang T, Ettner SL, et al. The implications of choice: Prescribing generic or preferred pharmaceuticals improves medication adherence for chronic conditions. Arch Intern Med 2006; 166:332–337. 17. Goldman DP, Joyce GF, Zheng Y. Prescription drug cost sharing: Associations with medication and medical utilization and spendcontinued on page 553 STUDY LIMITATIONS As mentioned earlier, the claims-based nature of our study meant that we were unable to account for several factors that had the potential to affect adherence. Patient factors such as socioeconomic status, body mass index, and health behavior or lifestyle were unavailable from claims data, as were physician attributes (e.g., their attitudes toward therapy and awareness of guidelines). Another limitation of claims-based data is its use in estimating adherence. Although the MPR methodology is widely used, by its definition it can generate higher-than-actual adherence. With this method, in addition, OAD side effects cannot be controlled for, and our retrospective study prevented us from drawing conclusions in terms of cause and effect. A problem inherent in claims-based analysis, despite the benefit that results from its real-world nature, is that its observational nature may produce selection biases. This can affect the interpretation of results, according to patient and physician selection. 540 P&T® • September 2008 • Vol. 33 No. 9

Table of Contents Feed for the Digital Edition of Pharmacy & Therapeutics - September 2008

Pharmacy & Therapeutics - September 2008 Contents Editorial Medication Errors Prescription: Washington New Drugs/Drug News/New Medical Devices Drug Forecast Effect of Prescription Copays on Adherence and Treatment Failure with Oral Antidiabetic Medications Vaccine Declinations Present New Challenges for Public Health Universal Health Care in America Digestive Disease Week and American Diabetes Association Pharmaceutical Approval Update

Pharmacy & Therapeutics - September 2008

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