Assessing cost of glimepiride as an add-on to metformin use in type 2 diabetic patients in improving quality of life

¹Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Universitas Andalas, Padang, Indonesia

^&Corresponding author
Najmiatul Fitria, Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Universitas Andalas, Padang, Indonesia

To the editors of the Pan African Medical Journal    

Type 2 diabetes mellitus (T2DM) is a chronic, multifactorial disease caused by genetic and environmental factors, characterized by insulin resistance and a progressive decline in pancreatic β -cell function. It is the most common form of diabetes, accounting for over 90% of global cases. In T2DM, the body's cells do not respond effectively to insulin, leading to high blood sugar levels. Initially, the body compensates by producing more insulin, but over time, insulin production becomes inadequate. According to the International Diabetes Federation (IDF), in 2021, there were 537 million people aged 20-79 living with diabetes globally, projected to reach 783 million by 2045 [1]. Indonesia ranks seventh worldwide and is the only Southeast Asian country in the top ten. In West Sumatra, the prevalence of diabetes was reported at 1.6% in 2018 and increased to 3.96% in 2019 [2]. Type 2 diabetes mellitus significantly impacts quality of life and requires consistent management to prevent complications and improve patient outcomes. Quality of Life (QoL) has been emphasized in recent years as a healthcare outcome [3]. The QoL is a key healthcare outcome, often assessed using the EQ-5D-5L, which includes five health dimensions and a visual analog scale (VAS) from 0 to 100. The quality of life for T2DM sufferers is considered lower than that of healthy people, so they require regular treatment to control blood sugar levels and improve quality of life [4].

However, diabetes treatment imposes a large economic burden on the country. According to the International Diabetes Federation (IDF), the costs associated with diabetes account for a sizeable increase in global health spending, regardless of whether those expenses are borne by people living with diabetes or by private or public payers, including governments. In 2017, costs reached 232 billion USD and increased to 966 billion USD in 2021 for adults aged 20-79 years [1]. Metformin is the most frequently prescribed antidiabetic because of its high effectiveness and low cost [5,6]. In addition, based on research by Sari et al., the cost-effectiveness of using a single oral antidiabetic, metformin, and the metformin-glimepiride combination, which has the value of the Incremental Cost-Effectiveness Ratio (ICER) of fasting blood glucose, is Rp 1,284.74; each decrease of 1 mg/dl means that the use of the metformin-glimepiride combination requires a higher cost but is more effective [7]. Diabetes treatment requires a lot of funds, such as treatment, transportation to health services, patient care, and other needs. The costs incurred during treatment are expected to provide beneficial therapeutic results and better quality of life. The antidiabetic metformin alone and the metformin-glimepiride combination were compared based on QoL gains and costs. The relationship between cost and quality of life can be seen in pharmacoeconomics through cost-utility analysis (CUA). In CUA, measurements are made using Quality Adjusted Life Years (QALYs) [8].

This observational, descriptive economic evaluation study was conducted at Universitas Andalas Hospital, Padang City, in February 2023, involving 69 purposively selected outpatients with type 2 diabetes mellitus. The study compared two treatment groups: metformin alone and a combination of metformin with glimepiride. Data were collected prospectively and verified through medical records. Inclusion criteria included patients aged 15-64 years, on consistent therapy for at least three months, with or without comorbidities. Patients with incomplete records, those who died or dropped out, pregnant women, or those unwilling to be interviewed were excluded. The study adopted a patient perspective, with a one-month time horizon and February 2023 as the index period. Costs were measured in Indonesian Rupiah (IDR) without applying discount rates, as data were within the same fiscal year. Cost variables included direct medical costs (medications, doctor visits, screenings, complication treatments) and indirect costs, while utility was assessed using the EQ-5D-5L questionnaire (Registration ID: 60040). A significance threshold of p < 0.05. The Incremental cost-utility ratio (ICUR) was calculated to compare cost-effectiveness between the two treatment groups. The education level of patients with type 2 diabetes mellitus at Universitas Andalas Hospital was categorized as low (no formal education or elementary), medium (junior or senior high school), and high (graduate or postgraduate). Most patients in this study had a medium level of education. Fewer patients had a high level of education, while the lowest number was found among those with low education levels. These findings are consistent with previous research which also showed that individuals with a high school education had the highest prevalence of type 2 diabetes mellitus [9].

The utilities of antidiabetic therapy observed in this study were the result of the conversion of utility values that were filled in by patients in the EQ-5D-5L questionnaire, which consists of a utility value and a visual analog scale (VAS). Antidiabetic cost-utility analysis in this study was calculated using the incremental cost-utility ratio (ICUR) value, as seen in Table 1. The average utility and direct medical costs are plugged into the ICUR formula. Antidiabetic drugs given to patients, alone or in combination, do not affect utility and VAS values. However, there is a difference between the average utility value of single metformin users and the metformin-glimepiride combination as 0.2, where the metformin-glimepiride combination is higher than single metformin. Meanwhile, the difference in the average VAS value in the two groups of antidiabetics was 1.422, with the metformin-glimepiride combination being superior. Both antidiabetic groups had an average VAS score in the moderate category. Antidiabetic cost-utility analysis in this study was calculated using the Incremental Cost-Utility Ratio (ICUR) value. The average utility and direct medical costs are plugged into the ICUR formula. The cost-utility of the metformin-glimepiride combination group compared with metformin alone can be explained using a cost-utility diagram (Figure 1). The incremental utilities are on the horizontal axis, and the incremental costs are on the vertical axis [2]. Once the costs and utilities of the metformin-glimepiride combination group are measured, it can be found in which quadrant the metformin single and metformin-glimepiride combination groups are located, which can help decision-making [9,10]. The average utility value of the single metformin and metformin-glimepiride combination group showed a difference of 0.2 with the metformin-glimepiride combination group having a higher value. Meanwhile, the difference between the two costs is IDR 5,157.00. Based on the cost utility diagram, the single metformin group and the metformin-glimepiride combination fall into the southeast quadrant (quadrant II), which illustrates that the costs required for the metformin-glimepiride combination are lower than the costs of single metformin, and the outcomes are also better.

Conclusion    

In conclusion, this study shows that adding glimepiride to metformin improves the quality of life for diabetes patients and provides better QALYs than metformin alone. The cost-utility analysis found that the combination therapy is more cost-effective. However, the ICUR result is only one part of the evaluation. Future studies should explore the sensitivity of the ICER to understand the economic impact better and address potential uncertainties in diabetes treatment strategies.

Competing     

The authors declare no competing interests.

Authors contibution     

Najmiatul Fitria: conceived and designed the study. Data were collected by Resna Rerita, Hansen Nasif, and Fatma Sri Wahyuni. Data analysis was conducted by Resna Rerita and Najmiatul Fitria. The manuscript was drafted by Najmiatul Fitria and Resna Rerita. All authors have read and approved the final version of the manuscript.

Acknowledgement     

The authors thank the Universitas Andalas Hospital for accommodating this study.

Table and figure     

Table 1: costs, utility, and incremental cost-utility ratio of metformin-glimepiride compared with metformin alone among patients with diabetes mellitus referred back to Universitas Andalas Hospital, Padang, Indonesia, from January to March 2023 (N=69)

Figure 1: cost-utility plan of metformin-glimepiride compared with metformin alone among patients with diabetes mellitus at Universitas Andalas Hospital, Padang, Indonesia, based on the study period from 2022 to March 2023 (N=69)

References