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Cro fab---Wyeth
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by new2hots on February 23, 2006
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Just out of curosity, in the Wyeth mix they used Bothrops Atrox. When they made Cro-fab whey did they not use B.Atrox
Garry
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RE: Cro fab---Wyeth
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by Cro on February 23, 2006
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The reason was because the Company only intended for Cro-fab to be used in the treatment of North American Rattlesnake, Cottonmouth, and Copperhead bites.
See http://www.rxlist.com/cgi/generic/crofab.htm for more information on the venoms of the four snakes that are used in making Cro-fab.
JohnZ
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RE: Cro fab---Wyeth
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by Phobos on February 24, 2006
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Venom Docs are learning that it's taking a hell of a lot of CroFab to treat a "typical bite" from even the for snakes used for the serum. I was told 20 to 50 vials for an EDB or WDB envenomation.
A real gravey train for Protherics at $1000 per vial.
I'll take good old Wyeth and get the job done with 6 to 10 vials.
Al
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RE: Cro fab---Wyeth
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by Rabies on February 24, 2006
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With EDB and WDB they are big snakes with copious amounts of venom, requiring a fair amount of antivenom to neutralise it. Bear in mind that if CroFab is used for those bites, that only 25% of the AV administered is specific to that animal.
Wyeth was also used in large amounts, 3-4yrs ago there was a WDB bite, 4week old animal, the patient required 20 vials of wyeth. Going back even further a 2-3yr old girl was bitten by a EDB and required 79 vials of wyeth. The down side to CroFab/Wyeth polyvalents is that 1 vial is not enough to neutralise an average venom yield of a particular snake,(EDB,WDB,Moj&Cottm..). If you look at the Australian polyvalent and monovalents, 1 vial has the potential to neutralise the average venom yield of the snake involved in its production, hence the lower dosage rates.
As Al mentioned, this could be the intention of the pharmacutical companies to gain as much financial reward as possible, in what normaly is accepted as being none profitable bi-product.
John
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RE: Cro fab---Wyeth
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by Chris_Harper on February 24, 2006
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20 to 30 vials of Wyeth was the typical range for EDB's. Since antivenom neutralizes venom molecule for molecule, 79 vials was probably overkill. Rattlesnakes don't meter out more or less venom because you are a child or an adult. But I'm sure the kid was really sick, and was probably "circling the drain" as we say in EMS. It puts the medical personnel in a "what other options do we have?" mode.
A few years ago, there was a 2 year old in Florida that rec'd 100 vials of Wyeth after being bitten on the thigh by a 4 foot EDB. 100 vials at 10 ml a vial is 1000ml of diluent. That's a lot of fluid to put into a 2 year old child. At any rate, the child ultimately died.
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RE: Cro fab---Wyeth
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by Chris_Harper on February 24, 2006
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Looking at that last point, another thing to consider about the difference between AV products is that snakes that utilize hemmorhagic metalloproteinases rather than post-synaptic neurotoxins, have a much higher venom yield in liquid volume. The target tissue is much larger - muscle, blood, and other protein structures, rather than neurotransmitter receptor sites. Therefore, it takes a higher number of antibodies to neutralize the injected venom of an EDB, which can have 4cc of venom, than it does an Eastern coral snake, which may only have .05cc's.
Even with regional polyvalents, such as SAIMR or the Indian AV's Bharat and Vins, it takes much less to treat the neurotoxic species than it does the hemotoxic species.
~CH
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RE: Cro fab---Wyeth
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by earthguy on February 24, 2006
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Does anyone make a monovalent for North American species? For those of us who are "professionals" (or at least really enthusiastic) it would be better if there were one antivenom per snake. That way, If I get bitten by one of my cottonmouths I could take the monovalent, and 100% of the antivenin would got to the neutralization of cottonmouth venom. I understand the need for polyvalent. 99% of the population can't properly ID any snake, let alone differentiate between a WDB and a canebrake or a copperhead and a baby cottonmouth (I can't tell you how often I have made house calls to remove "diamondbacks" and "copperheads" only to find a really nervous ratsnake). So...does anyone make it?
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RE: Cro fab---Wyeth
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by Phobos on February 24, 2006
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Joshua:
We're lucky to have what we have. These serums are not profitable for the companies to produce. They only do it because Congress mandates it via the "Orphan Drug Act"
Keep in mind when CSL serum is used it's a 50ml vial, not a 10ml vial like all of the others. To make a valid comparison, vial to vial, this needs to be taken into account. A more precise way of meauring it's effectiveness is by testing how many mouse LD50's is neutralized by each ml of serum. Yes, I know mouse vs human...It's really the only animal data we have for LD50's. Since we can't very well test for human LD50's neutralization titers. If they ever do that I know several candidates for the experiment.
As Chris mentioned, what is the clinical measure being used for a effective dose of? There really is none. This was discussed at the Snakebite symposium in October. Venoms with less enzymatic action like some of the neroutoxic snakes need to be judged differently than an snake with a predominate enzymatic venom which is NOT neutralized by A/V. Swelling and local effects tend to persist long after they typical coagulopathies have been corrected. Pumping huge amounts of Horse serum into somebody is just going to further complicate the clinical picture down the road when it pummels the kidneys and they shut down. I know from experience having processed 60ml of Wyeth many years ago. That may have been more uncomfortable than the bite it's self. While in Australia some poor mountain climber slide down a rope right on a 6 ft Tiger Snake!! OUCH!! He recieved 22 vials of CSL Tigersnake A/V at 50ml/vial he got over a liter of Horse Serum...oh what fun!
CroFab, being a smaller molecule is missing the part of the IgG molecule implicated in allergic reactions. It clears the blood stream faster than whole serum unlike Wyeth and is easier on the Kidneys. CroFab's shorter persistance means the IgG molecules may leave the body before finding the specific antigen to bind with. This is part of the mechanism that is clinically recognised as the "rebound effect"
What it all boils down to is that any envenomation is a serious medical event that tests the medical community across the board. From the Paramedic in the field to the Drug companies formulating the serum. No one has a perfect solution.
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