Express Scripts, OptumRx and CVS Caremark are the three largest pharmacy benefit managers (PBMs) in the US, and together account for most of the mail order market through their health plan and self-insured employer customers. Each has different brand and generic manufacturer contracts, and each has multiple networks of mail order, specialty and retail pharmacies, that it configures based on the client. Likewise, pharmacies have contracts with multiple wholesalers. So for example whether or not riluzole gets turfed out to specialty pharmacy depends on the combination of PBM and plan.
Manufacturers pay millions of dollars in rebates (volume discounts, if you will) to the PBMs. Some contracts are more exclusive than others.
In the States, if you there is a shortage of something you need, options include calling around to see if a pharmacy in your plan (even if not the one you normally use) has access to stock, paying cash to a non-network pharmacy that has stock [then submitting the expense to your plan with a med necessity letter], and appealing to your health plan to reimburse a non-contracted drug, e.g. in this case, a newer formulation of riluzole that is not yet on formulary, with an appropriate rx. Of course, if there are multiple drugs in a class, and one is in shortage status, there is often another drug in the class that can be used with an rx from your doc.
