CVS Dropped Zepbound From Its Formulary. Here's the Question That Matters More Than Which Drug Won.

When CVS Caremark announced it would exclude Zepbound from its standard formulary in favor of Wegovy, most of the coverage treated it as a story about two competing weight-loss drugs and which one won a negotiation. For employers, that framing misses the point entirely. The real story is that a decision affecting the clinical care and out-of-pocket cost of every covered employee on a GLP-1 was made by a third party, based on criteria the employer never saw, and most plan sponsors found out about it from a press release rather than a conversation with their own PBM. GLP-1s are now projected to account for roughly 14% of all prescription drug spend in 2026. A drug category that large should not be governed entirely by formulary decisions employers can't see and didn't request.

The Misconception

Employers evaluating GLP-1 coverage almost always frame the problem as a utilization question: how many members are on these drugs, what does each fill cost, and how do we control volume through prior authorization or a weight management program requirement. Utilization matters, but it's the wrong first question. The prior question is which specific drug your members are being steered toward within the class, and whether that steering reflects the lowest net cost to your plan or the largest rebate to your PBM. Semaglutide and tirzepatide are not interchangeable from a rebate economics standpoint, and neither are the various formulations and dose pens within each molecule. A PBM's preferred-drug decision inside the GLP-1 class can move your plan's total spend by a meaningful margin before a single utilization management tactic is even applied.

Why This Gets Overlooked

Formulary management has historically been one of the most delegated functions in the entire PBM relationship. Employers set plan design, deductibles, copay tiers, prior authorization requirements, and then hand the question of which specific drug sits in which tier to the PBM's clinical and contracting teams, on the reasonable assumption that formulary committees are making decisions based on clinical equivalence and cost. For most drug classes, across a long history of generic and therapeutic substitution, that assumption held up well enough. GLP-1s break the pattern, because the products aren't interchangeable generics, they're branded, high-rebate, high-demand drugs where manufacturers are competing aggressively for formulary position, and the value of winning that position is large enough to shape the negotiation independent of net cost to the plan.

A Framework for Evaluating Your Plan's GLP-1 Position

Four signals reveal whether your plan's GLP-1 coverage is optimized for your cost, or optimized for your PBM's formulary economics.

1. Which specific GLP-1 is preferred, and can your PBM explain the net-cost rationale in writing?

Ask directly: of the GLP-1 products approved for your covered indications, which is preferred on your formulary, and what is the net cost comparison, after rebates, against the alternatives. If the answer is a list price comparison rather than a net cost comparison, you're seeing the number the PBM wants you to see, not the number that determines your plan's actual spend.

2. Does your utilization management design push toward the lower-net-cost drug, or just toward lower utilization overall?

Prior authorization and step therapy are often described as cost controls in general terms, but the specific design matters. A step therapy protocol that requires members to try the preferred formulary drug before a non-preferred alternative is a utilization management tool doing double duty as a formulary-steering tool. That's not inherently a problem, but it means your utilization management strategy and your formulary strategy are the same decision wearing two names, and you should evaluate them together rather than as separate levers.

3. How is site of care and dispensing channel routing your members, and does it change your cost?

GLP-1s dispensed through a specialty pharmacy channel, a retail channel, or increasingly through direct-to-consumer manufacturer programs can carry meaningfully different net costs to the plan even for the identical drug and dose. Some manufacturers now offer cash-pay programs priced below what a plan pays through standard PBM channels for the same product. Your PBM has limited incentive to route you toward a channel that reduces the PBM's own revenue, even when it would reduce your plan's cost.

4. How do manufacturer copay assistance programs interact with your plan's cost-sharing design?

Copay accumulator and copay maximizer programs determine whether manufacturer coupon dollars count toward a member's deductible and out-of-pocket maximum, or whether the plan captures that value separately. For a drug class where manufacturer assistance can cover a meaningful share of a member's out-of-pocket cost, the accumulator or maximizer design your plan has in place changes both the member experience and the plan's real net cost, and it's frequently set up during initial plan design and never revisited as the GLP-1 category has grown.

What This Looks Like With Real Numbers

Illustratively, consider a plan with 150 members on a GLP-1 for either diabetes or weight management. If the PBM's preferred product carries a modestly higher net cost per member per month than a clinically comparable alternative, even a difference in the range of $50 to $100 monthly, which is plausible given how rebate-driven this category has become, that gap compounds to well over $100,000 annually across the covered population, before any utilization growth is factored in. That's a cost variance driven entirely by which drug sits in the preferred tier, independent of how many members are using the category or how tightly prior authorization is written.

Connecting This to Contract and Renewal

Formulary rationale disclosure is one of the specific reporting elements now expected under the 2026 transparency reforms working through Congress and the Department of Labor. That creates a natural opening: at your next renewal or quarterly business review, request the net-cost rationale for your GLP-1 formulary position as a standing agenda item, not a one-time question. If your PBM contract doesn't currently give you the right to request a substitution of the preferred drug based on your own net-cost analysis, that's a specific, addressable provision to raise before your next renewal cycle, particularly given how quickly manufacturer rebate offers in this category are shifting.

Actions to Take Now

Pull your claims data for the GLP-1 category over the last two quarters and identify exactly which products your members are filling, broken out by molecule and formulation. Request, in writing, your PBM's net-cost rationale for the currently preferred product in the class. Review your prior authorization and step therapy criteria specifically for GLP-1s to confirm whether they're structured around cost or simply around slowing utilization broadly. And check whether your plan's copay accumulator or maximizer program was designed before GLP-1s became a significant share of spend, since a program built for a different drug landscape may no longer serve your plan's interests as written.

Key Takeaways

The GLP-1 coverage conversation that matters most for 2026 isn't whether to cover these drugs or how tightly to manage utilization. It's whether the specific product your plan has been steered toward reflects your plan's cost interests or your PBM's rebate interests, a distinction that's easy to overlook because it happens one formulary tier away from where most benefits teams are looking. Getting a clear, written answer to that question is one of the highest-leverage conversations you can have with your PBM this year.