Which drug has been legalized in some states for use for medical purposes with a prescription?

Marijuana is legal for medical purposes in 30 states

Thirty states and Washington, DC, allow marijuana for medical purposes, although their approaches can significantly differ.

Some allow medical marijuana dispensaries and home cultivation. Others only allow home cultivation. And a few allow dispensaries but not home cultivation.

delegated (sometimes called enumerated or expressed) powers are specifically granted to the federal government in article i, section 8 of the constitution. this includes the power to coin money, to regulate commerce, to declare war, to raise and maintain armed forces, and to establish a post office.