I'd like to link to MedlinePlus, but only if I can frame it. Why don't you allow this?

Answer:

MedlinePlus contains licensed content from authoritative sources such as the American Society of Health-System Pharmacists, and the A.D.A.M. encyclopedia. Our license agreements do not permit framing of their content from our site. For more information, please see our copyright page.
For the safety and privacy of our users, we have blocked all framing.
Please see our guidelines on linking to MedlinePlus for further information.