Abstract
The future biosimilar insulin marketplace could be a bane, benefit, or something in between, to patients under our care in the United States. Formulary preferred product status, with or without FDA interchangeability designation, coupled with current and proposed state pharmacy substitution laws may lead to an environment with as many as 50 different substitution guidelines depending on in which state a patient presents his or her prescription to be filled. If online global prescription supply options, often referred to as "Canada Drug," are utilized, other country substitution guidelines come into play, which may yield a recipe for confusion, if not disaster.