What does plan-NDC pair mean?

A plan-NDC pair is one drug-strength-package code (NDC) listed on one Medicare Part D plan's formulary. The CMS Part D Formulary file is organized this way — each row represents one combination.

This is why counts in our data sometimes exceed the total plan count of 329. A single drug like rivaroxaban appears on many NDCs (different strengths, different package sizes), and each plan covers many of those NDCs. So the count 'Tier 3: 1,701 placements' for rivaroxaban means there are 1,701 plan-NDC pairs where rivaroxaban is placed on Tier 3 — across 329 plans and the various NDCs each covers.

When interpreting our data: a high plan-NDC pair count for prior authorization or step therapy means that restriction is broadly applied across plans and NDCs. A low count means the restriction is narrow or rare.