|MadSci Network: Medicine|
The concept of targeting drugs is a major focus in modern pharmacology. The general manner in which a drug is targeted is to couple it to something that will react selectively with a protein or other component of a tumor cell or some other component of the target tissue. Sometimes antibodies can be used. Most of the time, some minimal degree of targeting is achieved by the mode of administration of the drug. For example, a nasal spray targets the drug largely to the nasal passages and the lungs, thus minimizing the amount of drug that gets into the circulation and thus the rest of the body. The idea of using a metal and magnetism is at least conceivable. However, the metal would have to be either ionized or covalently bound to the drug (or drug carrier). I don't believe that it could be magnetic under such (chemical) circumstances. In addition, the magnets would presumably be applied from outside the body and thus would not achieve very good (spatial) resolution. But keep thinking, it's not a bad idea, and someday someone is going to come up with some feasible ideas to make it work. It would certainly enhance therapeutic responses while minimizing adverse effects.
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