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New insulin products were the go-to choice for U.S. adults with type 2 diabetes in the last half decade, researchers reported.

According to a serial cross-sectional study of ambulatory insulin use over the past 5 years, newer insulin products FDA approved after 2010 were much more frequently used, accounting for 18.1% of total treatment visits in 2016 (1.1 million visits, 95% CI 0.8-1.4 million), and jumping to 40.9% of total visits in 2020 (2.0 million visits, 95% CI 1.5-2.5 million), reported Rita R. Kalyani, MD, MHS, of Johns Hopkins University School of Medicine in Baltimore, and colleagues.

During this same time, older insulins that were approved prior to 2010 dropped out of favor, they wrote in , with older insulins making up nearly 90% of all patient treatment visits in 2016 versus 18% by 2020.

As far as insulin classes, long-acting insulin was the top favorite among Americans, accounting for about approximately two-thirds of treatment over the past few years -- for instance, 3.7 million visits in 2020 (95% CI 3.0-4.4 million). These included insulin glargine, levemir, and degludec products.

Rapid-acting insulins -- lispro, aspart, faster-acting aspart, glulisine -- were the second most common class. Across all years, premixed, intermediate-acting, and short-acting human insulins were seldom used.

Overall, analog insulins dominated, making up more than 80% of total treatment visits across all years (for example 4.3 million visits in 2020, 95% CI 3.4-5.1 million). These included glargine, levemir, degludec, lispro, aspart, glulisine, premixed analog insulin products. On the other hand, human insulins -- including NPH, regular, and premixed human -- only made up 5.5% of visits in 2020 (0.3 million treatment visits, 95% CI 0.1-0.4 million).

Of all the insulin molecules, insulin glargine seemed to be the most popular choice in the U.S. over the past 5 years. Insulin glargine was opted for in about half of all treatment visits from 2016 to 2020 (for example, 2.6 of 4.9 million visits in 2020, 95% CI 2.1-3.1 million).

"Insulin glargine's continued predominance, relative to newer insulins, may be due to several factors, including clinical inertia, which has been commonly described in the treatment of patients with type 2 diabetes," the researchers pointed out. They added that "expert guidelines note that analog basal insulins, including insulin glargine, are associated with less hypoglycemia compared with NPH (isophane) human insulin."

However, they also highlighted that "insulin glargine U300 and insulin degludec may be associated with less hypoglycemia compared with insulin glargine U100 or insulin detemir," citing the most recent , and the joint type 2 diabetes management algorithm from the .

Use of biosimilar insulins, which were first approved in 2015 and now include biosimilar glargine and biosimilar lispro, increased from 2.6% in 2017 (0.1 of 5.3 million visits, 95% CI 0.04-0.2 million) to 8.2% in 2020 (0.4 million visits, 95% CI 0.2-0.6 million) of total insulin treatment visits. In July 2021, the FDA approved Semglee (insulin glargine-yfgn) as the first interchangeable biosimilar insulin product, allowing for pharmacy-level substitution for Lantus (insulin glargine) in states that allow it.

In terms of insulin delivery, insulin pens also saw an uptick in adoption in the study time period, increasing from 36.1% in 2016 (2.2 of 6.0 million visits, 95% CI 1.7-2.7 million) to 58.7% in 2020 (2.9 million visits, 95% CI 2.3-3.5 million). In contrast, the use of insulin vials and insulin syringes dropped off.

But total ambulatory visits for any type of insulin treatment seemed to taper off in recent years, the authors noted, going from a peak of 6.0 million visits in 2016 to a low of 4.9 million visits in 2020, for an 18% decline.

The COVID-19 pandemic may be in part to blame for this decline, Kalyani's group suggested, writing that "insulin affordability and accessibility have been critically important to address, both prior to and during the pandemic. Federal and state legislations to have been brought forward."

"Moreover, many pharmaceutical companies have been placing maximum caps on patient copays for insulin or offering other patient assistance programs during this time. International emergencies, such as the current pandemic, may alter the course of insulin prescribing, and further research should examine future trends," they suggested.

The analysis included data on 27,860,691 insulin treatment visits in the U.S. that occurred between 2016 and 2020. About 44% of all visits were for patients ages 60 to 74. More than half of the patients were white, followed by about 18% Black, and around 16% Hispanic.

Data on visits were collected in IQVIA's National Disease and Therapeutic Index, which is a nationally representative audit of outpatient care including all types of payers. This audit samples 4,800 physicians quarterly, representing a random sample from the master lists of the American Medical Association and the American Osteopathic Association.

For each calendar quarter, these sampled physicians completed a form for 2 days consecutively for visits for each of their patients, including data on diagnoses, treatments, and demographic information. Office and telephone/telemedicine visits for patients with type 2 diabetes were included.

"These findings are of broad relevance to patients, clinicians, and policy makers invested in improving access to and affordability of insulins in the United States," Kalyani's group concluded.

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