Formulary Access
Whether and how a payer's formulary covers a drug, and at what tier, which directly shapes prescribing behavior.
Formulary Access describes whether a payer's formulary covers a given drug, and at what tier, which in turn sets the copay, prior authorization, and step therapy hurdles a patient faces in filling it. A drug can be clinically the right choice for a patient and still go unfilled if it sits on a disadvantageous tier or requires a prior authorization a busy practice doesn't have time to chase.
This is why formulary status shapes prescribing behavior as much as clinical evidence does in practice. An HCP who knows a competitor product has cleaner formulary access on the plans their patients actually carry will often default to it, regardless of which product a brand's own marketing favors. Commercial teams track formulary access account by account for exactly this reason, since it changes what message is actually worth leading with.