Using administrative data to compare the relative effectiveness of amlodipine vs nifedipine CC

OBJECTIVE

To describe an approach for using claims data to compare the effectiveness of 2 similar drugs used for similar indications within a health maintenance organization.

STUDY DESIGN

A database study comparing the effectiveness of amlodipine and nifedipine CC in the initial treatment of hypertension.

PATIENTS AND METHODS

The claims records of Pennsylvania Medicaid patients between 18 and 64 years of age with continuous eligibility in 1994 were studied. Pharmacy, hospital, and outpatient claims data were merged, and adult patients receiving the target drugs for the specified indication were identified. The effectiveness of the 2 agents used were compared based on the concept that a change in dispensed medication suggested either an adverse event or lack of effectiveness. Adherence rates, adverse events, and pharmacy and nonpharmacy costs associated with the 2 agents were also compared.

RESULTS

Patients receiving amlodipine and nifedipine CC as initial treatment for hypertension had similar demographic characteristics and numbers of comorbid conditions. More patients started on nifedipine CC switched to another calcium channel blocker (15.8% for nifedipine CC vs 10.3% for amlodipine). More patients started on amlodipine switched to another class of antihypertensive agent (13.2% for amlodipine vs 7.3% for nifedipine CC). Patients in both groups received adjunctive antihypertensive drugs at a similar frequency (35% for nifedipine CC vs 42%, for amlodipine). Rates of adherence were similar. In adherent patients, there was no difference in rates of reported adverse events. The nonpharmacy costs were similar between groups. Patients in the amlodipine group also had a trend toward higher overall pharmacy charges (all medications) and higher charges for antihypertensive medications other than the study drugs ($302 vs $188, P = .054).

CONCLUSIONS

Claims data are often the best available evidence for comparing the effectiveness of pharmaceuticals in real clinical practice. While these comparisons have inherent limitations, the accuracy of the assessment can be maximized by limiting the assessment to agents with the same specific indications. Other important elements include comparison of crossover rates to other pharmaceuticals in the same class; rates of addition of other pharmaceuticals in the same class, adherence, adverse events, and overall healthcare charges.

Clinical outcomes in statin treatment trials: a meta-analysis

OBJECTIVE

To determine the risk of cardiovascular events and death in patients receiving statin treatment for cholesterol regulation.

METHODS

Systematic review and meta-analysis of all randomized controlled trials that were published as of April 15, 1997. Primary or secondary prevention trials or regression trials were eligible.

MAIN OUTCOME MEASURES

All-cause mortality, fatal myocardial infarction (MI) or stroke, nonfatal MI or stroke, angina, and withdrawal from the studies. Both random- and fixed-effects models were run for the outcomes of interests, and results are expressed as odds ratios (ORs). Sensitivity analyses tested the impact of the study type and duration, statin treatment type, and control arm event rates. Intent-to-treat denominators were used whenever they were available, and the number needed to treat was calculated when appropriate.

RESULTS

Seventeen studies (21 303 patients) were included (2 secondary prevention studies, 5 mixed primary-secondary prevention population studies, and 10 regression trials). Treatment groups included lovastatin (t = 5), pravastatin (t = 10), and simvastatin (t = 3). For all-cause mortality, the OR was 0.76 (95% confidence interval [CI], 0.67-0.86) in favor of receiving statin treatment; for fatal MI, the OR was 0.61 (95% CI, 0.48-0.78); for nonfatal MI, the OR was 0.69 (0.54-0.88); for fatal stroke, the OR was 0.77 (95% CI, 0.57-1.04); for nonfatal stroke, the OR was 0.69 (95% CI, 0.54-0.88); and for angina, the OR was 0.70 (95% CI, 0.65-0.76).

CONCLUSIONS

Patients who received statin treatment demonstrated a 20% to 30% reduction in death and major cardiovascular events compared with patients who received placebo. This advantage was generally present across study types and statin treatment types and for patients with less severe dyslipidemias. The benefit in clinical outcomes was noticeable as early as 1 year.