Each Medicare Part D plan has a list of covered drugs that are called a formulary. Within every formulary, there are a set of rules applied to the prescription drugs covered by the plan. One of those rules is called step-therapy. If you get a prescription for a medication that has step-therapy rules, there is a process you will have to go through depending on the kind of drug you were prescribed (generic, preferred generic, brand name, etc.). There can be several drugs that are therapeutically equivalent, which means they essentially do the same thing but may have slightly different ingredients. Think of buying a generic brand of ibuprofen vs. buying Motrin ibuprofen over the counter at a drug store. There are the same variations for prescription drugs as well. Step Therapy is a process that requires members to start with the most cost-effective drug (the first step) and only move on to other, more expensive, or risky medications (additional steps) if necessary. The exact number of steps and requirements can vary depending on the drug.