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Driven by payments for diabetes treatments — especially insulin — prescription drugs for metabolic diseases now make up nearly one quarter of total national pharmaceutical spending, reported a study of spending trends by therapeutic class.

The detailed examination of a decade's worth of US drug spending also found changes in who pays for the medicines, with an overall drop in out-of-pocket costs, except in the metabolic disease category. The findings add to concerns about the costs of US diabetes treatments.

Annual US spending on diabetes medicines surged from $27.2 billion in 2011 to $89.2 billion in 2020, wrote Tyler Varisco, PhD, PharmD, and graduate student Whanhui Chi, both of the University of Houston, Houston, and their coauthors. Their paper was published online in Research in Social and Administrative Pharmacy.

In the same period, total annual pharmaceutical spending rose at a far slower rate, increasing from $341.5 billion to $473.1 billion. The top five therapeutic areas are metabolic (about 23% of total annual prescription spending), central nervous system (14%), anti-infectives (8%), cardiovascular (8%), and respiratory (8%).

The metabolic drug category topped spending for all 10 years of the study, despite a decline in a former blockbuster class of medicines for another chronic condition, high cholesterol.

In the antihyperlipidemic class, spending for treatments plunged with the widespread use of generic medicines. Annual spending on lipid-lowering drugs fell from about $29 billion in 2011 to about $8.1 billion in 2020, Varisco and colleagues reported.

Yet much of the persistent gain in the cost of diabetes treatments in this same period was due to a decades-old drug, insulin, a cornerstone of diabetes care.

Insulin Spending Rises

Annual insulin spending rose during the study period from $14 billion to $38 billion.

Biotech forms of insulin have been sold in the United States since the 1980s, with formula changes in the early 2000s that allowed for longer-acting shots. In 2022, Medicare Part D plans still had annual costs of $2000 to more than $3000 per patient for many insulin products, according to an online dashboard created by the Centers for Medicare & Medicaid Services.

"There's no reason that insulin costs what it costs," Varisco told Medscape Medical News.

There have been recent moves to cap what consumers pay for insulin. Medicare, which covers people aged 65 years and older in the United States, led the way putting in a $35-per-monthly-prescription cap in 2023 for its Part D pharmacy plans. (People taking several forms of insulin thus pay more than $35 out of pocket, as Medscape Medical News has reported.) Eli Lilly and other manufacturers then agreed to this approach for younger insulin consumers, starting this year.

But one company already has announced a plan to stop selling an insulin product in the United States. Novo Nordisk will discontinue its Levemir FlexPen and vial as of December 31, 2024. The company said this is due to global manufacturing issues and decreasing patient coverage and its confidence that US patients will be able to find alternative treatments.

Three US senators said this move to discontinue Levemir came after Novo Nordisk announced it was cutting the medication's price and shortly before the price reduction was about to go into effect. This decision raises questions and concerns for the health of those depending on Levemir and the stability of the insulin supply chain and market, Sens. Jeanne Shaheen (D-NH), Raphael Warnock (D-GA), and Elizabeth Warren (D-MA) said in an April letter to Novo Nordisk.

We "are alarmed by Novo Nordisk's decision to discontinue Levemir before allowing the price reduction to go into effect and are concerned that Novo Nordisk failed to take into consideration patient access to affordable, long-acting insulin substitutes prior to the discontinuation," the senators wrote.

In their paper, Varisco and coauthors said the medical community needs to keep an eye on the promises of Lilly and rivals in the diabetes market, such as Novo Nordisk as they promote newer glucagon-like peptide 1 receptor agonist (GLP-1 RA) semaglutide and the dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptors tirzepatide drugs, which have become wildly popular due to their potential to aid in weight loss, they wrote.

"Despite manufacturer assurances of insulin price controls, the increasing reliance on...(these) analogs and their dual indication in obesity may contribute to the increase in antidiabetic expenditures in the coming decades," Varisco and coauthors wrote in their paper.

For their research on drug spending, Varisco, Chi, and coauthors drew from 2011 to 2020 versions of household respondents to the Medical Expenditures Panel Survey, which is a set of large-scale US surveys of families and individuals, clinicians, and employers.

Medicare's purchasing of drugs grew markedly over the decade. The giant federal health program for people aged 65 years and older and those with disabilities accounted for 22% of payments for prescription medicines in 2011 and almost 40% in 2020. The share of drugs covered directly by consumers as out-of-pocket expenses declined from 19% to 9.7% in the same period.

$57 Million to $5.7 Billion

Federal officials are now contending with the cost of GLP-1 drugs for the Medicare program.

While there remains a prohibition against Medicare covering these drugs for weight loss, other uses of these medicines, including the prevention of cardiovascular events, will allow more people enrolled in Medicare to get them, wrote Juliette Cubanski and Tricia Neuman, researchers with the nonprofit KFF, formerly known as the Kaiser Family Foundation, in a March report.

Total gross Medicare spending on the three newest versions of the GLP-1 diabetes medications — semaglutide (Ozempic and Rybelsus, Novo Nordisk) and the dual GIP/GLP-1 agonist tirzepatide (Mounjaro, Eli Lilly) — rose from $57 million in 2018 to $5.7 billion in 2022, the KFF researchers wrote. (These figures do not account for rebates that can lower spending.)

Varisco cited the drug negotiation provisions in the Inflation Reduction Act (IRA) of 2022 as an important step toward addressing rising costs of medicines.

The IRA law gave Medicare some limited authority to negotiate with drugmakers on the costs of medicines, with the first price reductions from this process due to kick in in 2026. The initial batch of drugs selected for negotiations include the Januvia diabetes pill (sitagliptin) and several insulin shots.

But consumers should be aware that there's been continued opposition to Medicare drug negotiations from the pharmaceutical industry, according to Merith Basey, MSc, executive director of Patients For Affordable Drugs, an advocacy group funded by Arnold Ventures Inc.

Her group has created the FightPharma.org website to track these efforts, including lawsuits filed by drugmakers. Among the efforts from Basey's group is an online petition asking the chief executives of pharmaceutical companies, including Novo Nordisk, to drop their legal battles against the Medicare drug negotiation process.

"The patients fought really hard for the reforms in the Inflation Reduction Act," Basey told Medscape Medical News. "We are seeing patients organizing patients right now to fight back against these lawsuits and urging the CEOs to drop the suits because of the impact that it's going to have on millions of people."

Varisco and colleagues reported neither outside funding nor conflicts of interest.

Kerry Dooley Young is a freelance journalist based in Washington, DC.