The Importance of Formulary Management for Pharmacies

A pharmacy that fills prescriptions without a formulary strategy is guessing. Formulary management is the discipline that keeps that guesswork out of the process, and it's become more important as drug spending climbs faster than almost any other line item in healthcare. U.S. medicine spending grew 10.6% in 2025 alone, averaging 9.3% annual growth over the last five years. For pharmacies, that growth shows up as tighter margins, more prior authorizations, and more patients asking why their medication suddenly costs different than it did last month.

For this piece, we brought in perspective from the team at MedReb8, who work daily with the rebate and cost data that sits underneath formulary decisions. Their read on the process informs a lot of what follows.

Formulary management isn't a back-office function pharmacies can ignore. It shapes what gets stocked, what gets substituted, and what a patient pays at the counter.

What Formulary Management Means

Formulary management is the ongoing process of deciding which medications a health plan, pharmacy, or health system will cover and prioritize, based on clinical evidence, safety data, and cost. The output of that process is the formulary itself: a list of approved drugs. But the list is just the artifact. The management part is the continuous work behind it, evaluating new drugs as they launch, reassessing older ones as evidence changes, and adjusting coverage as prices shift.

That distinction is why the process never stops: a formulary that goes untouched stops doing its job. Drugs lose patent protection. New evidence surfaces on existing therapies. Cheaper, equally effective alternatives enter the market. A formulary frozen in place from two years ago is already out of date, which is why most pharmacy benefit managers update theirs at least twice a year, and some move to quarterly reviews.

Open, Closed, and Tiered Formularies

Not every formulary works the same way. An open formulary covers most drugs with minimal restriction, trading cost control for flexibility. A closed formulary only covers drugs specifically listed, which tightens costs but narrows options. Most commercial plans now run tiered formularies instead, where drugs are grouped into cost tiers (generic, preferred brand, non-preferred brand, specialty) and the patient's copay scales with the tier. This is the structure most pharmacists deal with daily, since it's what determines the copay conversation at pickup.

Who Decides What's on the Formulary

Formulary decisions run through a pharmacy and therapeutics committee, usually called a P&T committee. The core objectives of a P&T committee are choosing preferred drugs and alternatives based on safety and efficacy, cutting therapeutic redundancy, and maximizing cost-effectiveness. It's a clinical body first, not a purchasing department.

Membership typically includes primary care and specialty physicians, pharmacists, and other health professionals, often joined by nurses, legal staff, and administrators. Members are generally required to disclose any financial ties to drug manufacturers or PBMs before voting, and some organizations keep committee membership confidential specifically to keep outside pressure away from the table.

The Pharmacist's Specific Role in the Process

Physicians and administrators sit on the committee, but pharmacists do most of the groundwork that makes committee decisions possible. They write the drug monographs the committee reviews, run the pharmacoeconomic comparisons between a new drug and what's already covered, and flag when a therapeutic class needs re-review because new evidence or new competition has entered the market. When MedReb8's formulary management services get pulled into this process, it's usually at this analytical layer, matching rebate and net-cost data against the clinical case for a drug, so the committee isn't voting on list price alone.

Why Formulary Management Controls Costs

The cost case for formulary management isn't theoretical. In 2022, gross pharmacy expenditures in the U.S. grew 9.4% year over year, reaching $633.5 billion in total spend. Every percentage point of that growth eventually ends up on a plan sponsor's ledger, an employer's benefits budget, or a patient's copay.

Generic substitution is the most familiar lever, but it's not automatically the cheapest one. A 2019 analysis of Colorado's all-payer claims database found that high-cost generics were, on median, 15.6 times more expensive than a lower-cost therapeutic alternative with the same clinical value. Switching to the cheaper option would have cut spending on those drugs by 88.3%. That gap exists because multiple generics can share an active ingredient while differing in form or strength, and without a formulary steering the choice, the pharmacy or the plan has no mechanism to default to the cheaper one.

Therapeutic interchange goes a step further, substituting a different but clinically comparable drug within the same class, not just a generic version of the same drug. One widely cited PBM analysis estimated that guideline-adherent therapeutic interchange across just eight drug classes could save more than $20 billion annually. That's the scale formulary decisions operate at once they're rolled out across a large patient population.

How Formulary Decisions Affect Patient Safety and Outcomes

Cost control gets the attention, but the clinical side of formulary management carries just as much weight. A well-run P&T process cuts therapeutic redundancy, meaning it doesn't leave five near-identical drugs on the formulary when one or two, backed by solid evidence, cover the same patients just as well. Fewer redundant options means fewer edge cases where a prescriber or pharmacist has to sort out which of several similar drugs actually fits a given patient.

Formulary reviews also function as an ongoing safety check. When new adverse event data comes in on a drug already on the formulary, that's a P&T committee agenda item, not a one-time approval that gets forgotten. Evidence-based inclusion means a drug's spot on the list isn't permanent just because it was added once.

What Happens When a Drug Isn't on the Formulary

A drug missing from the formulary doesn't mean a patient can't get it. It usually means the standard coverage pathway doesn't apply, and the prescriber has to request a formulary exception, providing clinical justification for why the covered alternatives won't work for that specific patient. Most formulary systems build this exception process in deliberately, precisely so a genuine clinical need doesn't get blocked by a list that was built around the general population, not any one patient.

The Adherence and Access Tradeoff

Formulary decisions can help adherence just as easily as they can hurt it. A nationwide Swedish study of statin refill adherence found patients exposed to generic substitution had a meaningfully higher adherence rate than those who weren't, 84.6% compared to 59.9%. Lower out-of-pocket cost, in that case, translated directly into patients actually continuing their treatment.

The friction runs the other direction too. Prior authorization and step therapy, both common formulary-driven requirements, exist to steer patients toward the preferred option first. But they also add a delay between prescribing and dispensing, and that delay is where some patients simply give up on filling the prescription at all.

One awkward reality underneath all of this: most consumers don't know their plan even has formulary restrictions until they hit one at the counter. That gap is where pharmacy staff end up doing informal patient education the formulary system assumes will happen somewhere else.

What This Means for Day-to-Day Pharmacy Operations

None of this stays theoretical once a patient is standing at the register. A pharmacist filling a prescription against a tiered formulary needs to know, in real time, whether a therapeutic interchange applies, whether a prior authorization is already on file, and whether the patient's copay just changed because the plan's quarterly formulary update went into effect. Point-of-sale systems that flag these automatically save real time. Ones that don't push the whole conversation onto whoever's behind the counter when the claim gets rejected.

That operational load is exactly why formulary management can't be treated as something that happens upstream and stays there. The committee sets the rules. The pharmacy lives inside them every single day, explaining a substitution, filing an exception, or walking a patient through why the drug they got last month isn't the one they're getting today.

Get the formulary strategy right, and most of that friction disappears before it ever reaches the counter.