Rich Wood wrote:

There aren't even pharmacutical companies advertising the drugs
Limbaugh uses.

Yeah, but that would be kind of bad form....sort of like an airline
commercial after a news item about a plane crash....

Not only is he defending their use, he's contributing
significantly to their bottom line. Still, no ad budget for his show.
That sounds pretty unappreciative on the part of the companies.

My guess is that they don't want to be seen as advocating *illegal*
use of their products by anyone, even as a "joke".