Quality of care and attributable healthcare costs in diabetic hypertensive patients initiated on calcium antagonist therapy

Background and objective: Calcium antagonists (CAs) from two classes - dihydropyridine and non-dihydropyridine (DCAs and NDCAs, respectively) - are important add-on agents in goal blood pressure (BP) attainment. This study compared drug regimens to which DCAs or NDCAs had been added; for each class, BP reduction and healthcare costs were evaluated in a diabetic hypertensive population. Design, setting and patients: This was a retrospective observational study using administrative claims data within two US health plans. Patients with diabetes mellitus (DM) and hypertension initiated on CA therapy between 1 January 2000 through 30 June 2002 were identified; the date the first CA prescription (CA-Rx) was filled in this period was labelled the index date. Inclusion required plan enrolment for 6 months pre- and 1 year post-index, no CA-Rx 6 months pre-index, and medication possession ratio >50% for 1 year post-index. Patients fell into either dihydropyridine or non-dihydropyridine study groups. Main outcome measures and results: For each group, costs (amounts allowed by plans, in US dollars; actual costs for 2000-2002) were calculated for resources attributable to DM/hypertension. A total of 5551 patients met eligibility criteria (NDCA = 1515; DCA = 4036). Most had been taking other antihypertensive I medications: 86% and 76% in the DCA and NDCA groups, respectively. The NDCA group had lower annual attributable costs than the DCA group ($US1637 [95% CI $US1479, $US1813] vs $US1989 [95% CI $US1823, $US2170]; p < 0.004). A total of 313 medical charts were reviewed (DCA = 242, NDCA = 71). Both groups had similar pre-and post-index BP values; mean changes in systolic and diastolic BP were not statistically significant between groups. Only 22% of all patients attained the recommended systolic/diastolic BP goal of <130/80mm Hg, and <45% of patients were tested for proteinuria during the study period. Conclusions: Patients initiated on an NDCA attained similar BP reductions compared with DCA at lower total healthcare costs. Opportunities exist for more aggressive management of BP and testing for proteinuria in DM patients with hypertension.