First of all, the “undue burden” standard was used pre-Dobbs to throw out state laws forcing women to jump through hoops before getting an abortion. It no longer applies to abortion post-Dobbs.
The Commerce Clause does not have an “undue burden” standard at all. It does prevent inappropriate burden of interstate commerce, but inappropriate means unfairly burdening other states. It is an anti-protectionist measure.
So for example if WV banned the import of mifepristone while allowing mifepristone to be produced and sold by West Virginian companies, this would be considered an inappropriate burden to commerce because it discriminates against other states.
States can still outright ban the sale of products in the state. Even products that have nationwide distribution and easy availability in other states, like fireworks and slot machines.
More generally, states are mostly responsible for medical licensing and prescriptions within that state. They can certainly regulate FDA approved drugs (after all, cocaine is FDA approved for some medical uses but is also subject to extensive state laws).
Mifepristone is in legally uncharted waters, but you shouldn’t assume that the Commerce Clause will necessarily protect it in this case.