I couldn't get decent info on antivenoms so I asked for some help from the PICU lists [no case details or names divulged!] and the responses are as follows:

  1.. I guess the other question would then be, how much of the antibody is 
  taken up by the digestive tract?  Or is the protein degraded by all 
  the trypsins, chymotrypsins, etc.  I would assume that some would be 
  taken up, or so the theory behind all the food allergies goes, but 
  breast milk has been shown to delay the intestinal epithelium immune 
  response to protein antigens.  Does that mean breast milk would be 
  protective?  Or does any exposure to formula rev up the immune 
  response?

  Yet another question is: how long would you ban mom from breast 
  feeding?  One month? Three months?  Two weeks?  Six hours?  Free Fab 
  levels are nearly at zero within 4 hours of administration for 
  envenomation, but total Fab levels can still be detected 9 days after 
  administration (J Int Med 241:53-58, 1997).  Clinical studies have 
  shown return of coagulopathy in as little as 2 days after 
  administration of the ovine antivenom (Arch Int Med 159(7): 706-10, 
  1999).  Does this mean that the antibodies are gone?  Is the free Fab 
  the important level?  Or the total Fab?  If it's free Fab, then nurse 
  when you see the whites of her eyes.

  My bias would be to discard the breast milk for two weeks, but that 
  is only a guess on my part.  
  2.. First of all it would be my suspicion that immediately after being nailed by 
  a copperhead snake, the mother would not be inclined to breastfeed.

  Secondly, the new antivenin is called CroTAb, not Corfab.  Snakes in the pit 
  viper class are called Crotalidae.  The timber rattlesnake, for example, 
  bears the colorful moniker Crotalus horridus.  CroTAb is comprised of a 
  combination of four specific binding antibodies directed like SCUD missiles 
  to the purified antigen-binding fragment (Fab portion of an IgG molecule) in 
  the venoms of four badass Crotalidae: Western diamondback rattlesnake, 
  Eastern diamondback rattlesnake, Mojave rattlesnake, and the cottonmouth or 
  water moccasin.  Since it is developed from innocent sheep rather than 
  immunologically jaded horses, CroTAb is more effective and has a lower 
  profile for mayhem, but still has about a 20% incidence for adverse reactions 
  and should not be used for just anything.

  Thirdly, the copperhead snake (Agkistrodon contortrix contortrix) belongs to 
  a somewhat different family of snakes, and its bite is not quite the scare of 
  envenomations from the Big Four.  CroTAb is not the treatment of choice.

  3.. In 1991 the Alabama Center for Envenomation looked for ovine antibodies-such

  as those used in antivenin immunotherapy in porcine milk (read pre-CroFab's

  Crotab by the then Therapeutic Antibodies). We found that fabulated ovine

  immunoglobin (lacking the Fc receptor) was not measurable in pig milk,

  whereas full ovine antibody (radio-labelled from precipitated sheep serum)

  was present at high concentrations in the porcine milk. This study suggested

  Fc mediated transport in breast acinar cells may participate in antibody

  levels in mammalian coelostum.


  Such observations raise questions about selection of xenospecies

  immunotherapy in the care of pregnant or lactating women. Therapies in

  question include digitoxin toxicity, botulism intoxination and in this case,

  envenomation by North American crotalids or agkistrodons. The results

  suggest that Fabs may have lower acinar transfer rates then polyclonal.

  non-fabulated immunoglobins.


  I should hasten to add that the study suffered from design flaws with regard

  to our immunoassay-which may have measured antigen on the (non-existent) Fc

  region of the ovine antibody molecule and therefore "missed" the fabulated

  antibody. Such possibilities are less likely as I re-ran SDS PAGE gels

  focusing on fabulated kD markers and found none.


  If you have human breast milk obtained by a patient treated with CroFab, we

  would be interested in testing it with a highly sensitive assay we produced

  in 1999.
In total then there seems to be a lack of absolute certainty - but concurrence that erring on the side of caution is wise.
Tony Knox

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