Why Drug Lists Are Reorganised Every Year

A drug plan covers a defined list of medicines, arranged into tiers that determine what the patient pays. Both the list and the tiers are rebuilt each year, and the reasons are commercial.

The list is a negotiating instrument

Plans agree prices with manufacturers, and the leverage in those negotiations comes from the ability to include or exclude a product, or to place it in a more or less favourable tier.

A manufacturer offering better terms can gain preferred placement, which directs more patients towards its product and away from competitors.

The result is that placement reflects the outcome of commercial negotiation as much as clinical distinctions between similar medicines.

Tiers translate into patient cost

Lower tiers usually carry a small fixed copayment, while higher tiers carry larger copayments or a proportional share of the drug's cost.

A medicine moving up one tier can therefore raise a patient's annual cost substantially even though the prescription, the dose and the pharmacy are unchanged.

Because the change happens at the plan's renewal rather than at the prescription's, it arrives without any prompt from the prescriber.

Generic entry reshuffles everything

When patent protection on a medicine expires and generic versions appear, plans typically move the generic into a preferred position and the branded original upwards.

This is the largest single source of annual reshuffling, and it usually reduces cost for patients who switch while raising it for those who do not.

Similar dynamics apply to biological medicines, where near-equivalent versions enter under their own regulatory framework and change the competitive position.

Access rules sit alongside the tiers

Beyond placement, plans apply requirements such as prior authorisation, quantity limits, or a requirement to try a lower-cost alternative before a more expensive one is funded.

These conditions can be added to a medicine that was previously available without them, which changes the practical accessibility even when the tier has not moved.

Exception processes generally exist where a clinician can document why an alternative is unsuitable, though the procedures and evidence required differ by plan.

The annual review is the only defence

Because changes are announced at renewal and take effect at the start of the plan year, the enrolment window is when a mismatch can still be corrected.

Checking each current prescription against the incoming list, rather than assuming continuity, is what reveals whether a different plan would now cost less.

Rules governing formularies, appeals and enrolment periods differ by jurisdiction and are revised over time, so current plan documents are the authoritative source.