Medicare Formulary Change Tracker

Tracks Medicare Part D formulary changes for the drugs you care about and reports every change as structured data:

• "Ozempic moved from Tier 2 to Tier 3 on this formulary (39 plans)." (tier_changed)
• "Prior authorization is now required." (prior_auth_added)
• "Step therapy added." / "Quantity limit changed from 2/28d to 1/28d."
• "The drug was dropped from this formulary entirely." (drug_removed_from_formulary)

Source: the official CMS Monthly Prescription Drug Plan Formulary files — the authoritative, complete record of every Part D formulary in the US, refreshed monthly. Drug names are resolved through the National Library of Medicine's RxNorm, so you can track by brand name ("Ozempic"), generic name ("semaglutide") or RXCUI — all dose forms are covered automatically.

Who uses this

• Pharma market-access teams — know the day your product (or a competitor's) gets a tier bump, PA or ST anywhere in Part D.
• Specialty pharmacies — anticipate reimbursement friction before prescriptions start bouncing.
• Benefit consultants & brokers — advise clients with plan-level facts.
• Healthcare analytics & investors — formulary positioning changes as a clean data feed.

How it works

Each run finds the newest CMS monthly release, extracts the formulary and plan-information files (a few MB via targeted range requests — not the full multi-GB archive), filters to your drugs' product RXCUIs, and diffs the coverage state of every (formulary × product) pair against the previous run's snapshot. Each change is enriched with plan context: how many plans use that formulary, sample plan names, contract ids and the states they operate in.

CMS publishes monthly — schedule the Actor weekly or monthly; runs between releases simply report zero changes.

Input

{
    "drugs": ["Ozempic", "Eliquis", "Jardiance"],
    "states": ["TX", "FL"],
    "contractIds": [],
    "emitBaselineRecords": false
}

Field	Type	Description
drugs *	string[]	Brand/generic names or RXCUIs, max 200. All product dose forms are tracked per drug.
states	string[]	Optional: only formularies used by plans operating in these states.
contractIds	string[]	Optional: only formularies used by these CMS contracts (e.g. H0028).
emitBaselineRecords	boolean	Push the full current coverage picture on the first run. A nationwide drug can span 500+ formularies × dose forms — thousands of records. Default false.
snapshotStoreName	string	Named key-value store for snapshots between runs.

Output

One dataset record per (formulary × drug product) change:

{
    "drug": "Eliquis",
    "product": "apixaban 5 MG Oral Tablet [Eliquis]",
    "rxcui": "1364445",
    "formularyId": "00026000",
    "planCount": 39,
    "samplePlans": ["Humana Gold Plus SNP-DE H0028-007 (HMO D-SNP)"],
    "contracts": ["H0028", "H1036"],
    "states": ["FL", "GA", "NE", "TX"],
    "changeType": "tier_changed",
    "previousTier": 4,
    "currentTier": 3,
    "priorAuthorization": false,
    "stepTherapy": false,
    "quantityLimit": "2/28d",
    "changes": [
        { "field": "tier", "kind": "tier_changed", "old": 4, "new": 3, "description": "Tier 4 -> 3 (more favorable)" }
    ],
    "sourceFileDate": "20260630",
    "detectedAt": "2026-07-10T18:08:50.965Z",
    "source": "CMS Monthly Prescription Drug Plan Formulary (Medicare Part D)"
}

changeType values

Value	Meaning
baseline	First run — current coverage state (opt-in).
tier_changed	Cost-sharing tier moved (see previousTier/currentTier).
prior_auth_added / prior_auth_removed	PA requirement toggled.
step_therapy_added / step_therapy_removed	ST requirement toggled.
quantity_limit_added / quantity_limit_removed / quantity_limit_changed	QL toggled or amount/days changed.
drug_added_to_formulary	Product newly covered by a formulary.
drug_removed_from_formulary	Product no longer on a formulary.

A run summary (CMS release processed, counts per change type) is stored under the OUTPUT key of the default key-value store.

Notes & limitations

• Scope: Medicare Part D (and MA-PD) formularies — the segment CMS publishes completely and machine-readably. Commercial/employer formularies are not included.
• Changes are detected at formulary level (CMS's unit of truth); the planCount/contracts/states fields tell you the blast radius of each change.
• The first run after the annual plan-year rollover (January file) naturally produces a large wave of changes — that's real (plans reset formularies yearly), not noise.
• This is data, not advice: verify critical decisions against the CMS files and plan documents.