QUESTION: Why such strict caution on the IM Iron package insert? I consulted a reference which did mention fatal anaphylaxis, but in less than 1% for IV. It’s also advised for slow drip only so I have assumed a rapid IM would present greater risk. IV iron gives me enough anxiety for AE’s so I just avoid IM all together. One serious AE was all I needed to keep me conservative in my treatments.
ANSWER: Sounds odd I know, but first, anaphylaxis ‘can’ happen with any parenteral means used, but the case of Iron is actually more common in the IV than IM form. The greatest reason being that the ‘allergy’ reactant is NOT iron but the sugar its attached to, and in the IV compartment you have body wise exposure to the ‘sugar’ or chelate whereas the IM compartment has a buffer and is more localized – so much less likelihood of a true anaphylaxis.
Second the package insert is two things that are both confusing:
1. It is written not for information but for the FDA, so safe use in the rest of the world (regardless of data to contrary) is ignored often.
2. As an FDA ‘tool’ the package insert borrows from other older inserts that were successful in order to get approval (i.e. the old Prometrium insert lifted lots from Provera even though it was a different chemical – just for approval. SO the package ignores safe use (ie as IM) elsewhere in the world – for approval sake). Death rates are troublesome but the most well done paper on it for Iron lists a total of 74 deaths likely due to Dextran forms and 2 possible for Venofer (Sucrose).
Wysowski, D. K., Swartz, L., Vicky Borders-Hemphill, B., Goulding, M. R. and Dormitzer, C. (2010), Use of parenteral iron products and serious anaphylactic-type reactions. Am. J. Hematol., 85: 650–654. doi: 10.1002/ajh.21794