Compliance with antihypertensive therapy in the elderly: a comparison of fixed-dose combination amlodipine/benazepril versus component-based free-combination therapy

Abstract

Background: Treatment regimens that require fewer dosage units and less frequent dosing to decrease the complexity and cost of care are among the strategies recommended to improve compliance with antihypertensive therapy. Simplifying therapy may be particularly important for elderly patients, who are more likely to have co-morbid conditions and to be taking multiple medications.

Objective: To determine rates of compliance with antihypertensive therapy and total costs of care among elderly Medicaid recipients treated with fixed-dose combination amlodipine besylate/benazepril versus a dihydropyridine calcium channel antagonist and ACE inhibitor prescribed as separate agents (free combination).

Study design: A longitudinal, retrospective, cohort analysis of South Carolina Medicaid claims for ambulatory services, hospital services, Medicare crossover, and prescription drug for the years 1997-2002. Follow-up was 12 months from the index date, defined as the first prescription dispensing date for a study drug.

Patients: South Carolina Medicaid beneficiaries aged >or=65 years.

Main outcome measure: Outcomes variables included compliance defined as the medication possession ratio (MPR), which was the total days' supply of drug (excluding last prescription fill) divided by the length of follow-up (with number of hospital days subtracted from the numerator and denominator). We hypothesized that elderly individuals receiving fixed-dose combination amlodipine besylate/benazepril HCl would be more compliant with therapy than those receiving a dihydropyridine calcium channel antagonist and ACE inhibitor as free combination.

Results: There were 2336 individuals in the fixed-combination group and 3368 in the free-combination group. The mean age was 76.0 +/- 7.2 years, and 82.6% were female. Compliance rates were significantly higher with fixed-dose versus free-combination therapy (63.4% vs 49.0%; p < 0.0001). The average total cost of care for patients receiving the fixed-dose combination was $US3179 compared with $US5236 (2002 values) for the free-combination regimen. In multivariate regression analyses on the log of total cost of care, average total costs increased by 0.5% for each 1-unit increase in MPR, and for each additional co-morbidity (measured by the chronic disease score) there was an increase of 10.4%. However, average total costs were reduced by 12.5% for patients using fixed-dose versus free-combination therapy (p < 0.003).

Conclusion: Use of fixed-dose amlodipine besylate/benazepril HCl by elderly Medicaid recipients was associated with improved compliance and lower healthcare costs compared with a dihydropyridine calcium channel antagonist and ACE inhibitor prescribed as separate agents.