Previous research on comparing different formulations of the same drug molecule has been mostly limited on establishing efficacy or effectiveness of products. In the case of metoprolol, existing literature documents clinical outcomes associated with MT and MS,12
but no research is available on how these two products compare with each other in terms of total health care costs incurred. The results of the current study show that the overall expenditures of hypertensive patients on twice-daily MT are not significantly different than the overall expenditures of once-daily MS. However, since the cost of a once a daily formulation is almost two times a twice-daily formulation, MS is associated with significantly higher out-of-pocket cost. The similarities in overall health care expenditure indicate that both the products are equally beneficial, and once daily MS may not offer any additional advantage to justify the additional drug cost.
Adherence is a major issue in the treatment of hypertension, especially if approximately 50% of the hypertensive population discontinues their antihypertensive medication within the first 6–12 months of initiation of therapy.16
MS being a once-daily formulation has a clear advantage over MT in terms of improving adherence by providing more ease to the patient. Previous studies have shown that simplification of dosing regimens using once-daily medications and/or combination medications does help in improving adherence to the regimen.6
Most of these studies show that there is no significant reduction in the blood pressure associated with increase in adherence to the treatment regimen with a once-daily regimen when compared with a twice-daily regimen in the treatment of hypertension.18
On the other hand, there are studies that show that once-daily medications not only improve adherence, but also decrease blood pressure, and are cost-effective as well.21
As a result, there is lack of established relationship between adherence and lowering of blood pressure.17
Hence, in this study, the similarity in overall expenditure questions the advantage of MS having a once-daily dosing regimen, as the total health care expenditure is a good predictor of the overall health status of a hypertensive individual. Currently, very little is known about the extent of difference in adherence required to produce any noticeable effect in terms of overall health status and health care expenditure. Further research is warranted to examine adherence rates in similar cohorts and its impact on overall health status. Although both MS and MT have a similar impact on total health care expenditure, one key difference to be noted is, only MS is indicated for the treatment of heart failure by the FDA.10
Heart failure is shown to be associated with hypertension.25
Therefore, in heart failure patients who are hypertensive, MS is an obvious choice given its FDA-approved indication for heart failure. Moreover, the pharmacokinetic profile of MT is associated with higher utilization of health care services and inferior outcomes when compared with MS in heart failure patients.26
In addition to the inferiority of MT, heart failure is associated with a higher risk of hospitalization, which can lead to increased costs; prevention of hospitalization with the use of MS can save money in the long run in this patient population.27
MT is available as a discounted generic in many pharmacies. The discounts available on MT have increased access to this medication, even with hypertensive patients who are uninsured.28
This access to medications at a deeply discounted price with the same efficacy will ensure that the hypertensive patients do not go without medications due to lack of insurance. The rising cost of prescription drugs presents a significant challenge to individual consumers. Finding affordable treatment options has become a very important need to reduce financial burden on both patients and payers. Future research should be carried out to produce more evidence towards economic comparison of different dosage forms of widely prescribed drugs such as metoprolol using diverse patient populations to generate potential cost savings without compromising health outcomes.
Some clinicians initiate therapy of MT as a once daily dose; however, with the MEPS database, it becomes difficult to identify these patients. The outcomes of this therapy are yet to be ascertained. Nonetheless, if the outcomes of this therapeutic regimen are similar to that of MT given twice a day and/or MS given once a day, there could be considerable reduction in the costs associated with the treatment of hypertension using MT. Further clinical and pharmacoeconomic research of this therapeutic regimen could present clinicians with other cost savings.
Given the sample size and the complexity of the characteristics and the disease of hypertension, the socioeconomic characteristics and their association with health care expenditure needs to be carefully interpreted from this study. Previous research has shown that females have higher overall expenditures, but males are associated with more spending on drugs, physician service, and hospital service.29
Although the results of this study do not show such association, it demonstrates that the expenditure to age correlation is supported by existing literature.29
In addition, previous studies have shown conflicting results for the association between expenditure and employment status and, hence, the results of our study should be carefully interpreted.29
In short, with the limitations of this study, which are listed below, such associations may not be fully confirmed based on a single study.