Background: Metoprolol, a selective beta-1 blocker, is available in two different salt forms in the market - metoprolol succinate (MS) and metoprolol tartarate (MT). Both the formulations are Food and Drug Administration approved for the treatment of hypertension. Several studies have shown similar efficacies between the two salts; however, they differ in their pharmacokinetic properties and are therefore priced differently. The primary objective of this study was to compare the overall health care expenditures of hypertensive patients on MT and MS to see if the price difference in the two preparations is offset by savings in overall expenditure.
Methods: Two cohorts of patients using MT and MS were selected from the 2008 Medical Expenditure Panel Survey. Propensity score matching technique was used to balance the cohorts on various parameters such as demographic information, insurance status, and comorbidity score. Patients using MT were matched to patients using MS on the logit of propensity score using calipers of width equal to 0.2 of the standard deviation of the logit of the propensity score. Multiple regression analysis was carried out to examine the association between health expenditure and type of metoprolol salt, adjusting for other covariates.
Results: A total of 742 patients were found to use metoprolol (MT-388, MS-354). After propensity score matching, a total of 582 patients were left in the sample for final analysis (291 patients in each cohort). The average annual health care expenditure was slightly higher in the MT cohort; however, after adjusting for covariates in a multivariate analysis, the difference was found to be statistically insignificant (P = 0.23).
Conclusion: Both the products of metoprolol were found to have similar average annual total health care expenditure; however, MS once a day has higher out-of-pocket cost.
Keywords: cost; hypertension; propensity score.