FAQs
Should Premedication be used to Prevent Transfusion Reactions?
I used to say, "Yes!" Now, not so much...
Before we get into this, let's talk about terminology and how the question was phrased. Truth be told, you probably cannot actually prevent the physiologic mechanisms of a transfusion reaction from occurring by giving someone a medication beforehand. All you can do with premedication is potentially mask the clinical manifestations of what has already occurred. Before I get too far ahead of myself, let's make sure you understand what "premedication" means.
Pre-transfusion medication (premedication) is most commonly a dose of roughly 325 mg of acetaminophen (a.k.a. Tylenol) and 25 mg of diphenhydramine (a.k.a. Benadryl), given a half hour or so before transfusion. On the clinical side, there is some disagreement on whether or not this works. Many people believe that giving premedication is the "lazy" way out, designed to give a resident or intern a chance to sleep through the night. Further, the argument goes, masking the manifestations of transfusion reactions is not only a lazy idea, but a dangerous one, too! "If my patient is having a reaction, I need to know about it, doggone it!"
Well, I'm certainly in favor of careful patient monitoring during transfusion, as well as for the prevention of interns and residents sleeping through the night (that's why I'm a pathologist, by the way!), but the argument calling this practice "dangerous" for reasons of "masking" significant reactions doesn't really make sense. Realistically, 325 mg of acetaminophen is not a lot, and it could really only prevent the febrile manifestations of a febrile nonhemolytic transfusion reaction, which is a benign reaction anyway! The fever of an acute hemolytic reaction would be highly unlikely to be affected by such a small amount of antipyretic medication! The same analogy applies for Benadryl: urticarial reactions could be suppressed (at least partly), while anaphylactic reactions wouldn't be affected in the least. So, in theory, you would only be preventing the manifestations of benign things that you don't care about anyway by using premedication.
Using the above rationale, up until recently, I have recommended routine premedication in my daily transfusion medicine practice. However, a very important article from Johns Hopkins published in Transfusion in 2007 (Transfusion 2007;47:1089-1096) not only punched some big holes in the above theory, but also raised some interesting points about toxicity of premedication. In short, this article looked at the available studies about premedication (which are few) and recognized that the data indicates that premedication just does not prevent febrile or urticarial reactions! How depressing! The authors (Tobian, King, and Ness) also raise some very good points about some potential effects of acetaminophen (hepatic) and diphenhydramine (neurologic), and they recommend that routine premedication should NOT be recommended. So, while many still consider premedication "standard," it may not be the best idea in light of current evidence.