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RE: What's up with Crofab use?
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by JoeCrotalid on September 17, 2011
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bwanadon, I am curious as to whether you are questioning the dosage given or that CroFab was used to treat copperhead bites. In all 3 cases, the amounts that were given are well within common dosages that may be needed to treat Agkistrodon, Sistrurus or Crotalus bites. Without actually having the patient chart to review, it is impossible to determine what was going on in any case. Normal dosing is a bolus of 4-6 vials, a repeat bolus of 4-6 vials if effects continue to progress until control and then 2 vial maintenance doses every 6 hours x3 with additional 2 vial doses as needed. So case #1 most likely indicates 2 bolus doses of 6 vials and the maintenance doses to equal 18 vials. Case #2 most likely indicates 2 bolus doses of 4 vial bolus doses and then the maintenance to equal 14 vials, and finally case #3 indicates a bolus of 6 vials and the 3 maintenance doses to equal 12 vials (which is extremely lucky for a C. adamanteus envenomation). The major pitfall in managing snakebites is administering too small a dose of AV which is why I usually recommend starting with 6 vials rather than 4 vials. Children are especially concerning is because of their smaller body sizes, and they usually tend to do worse with envenomations than adults due to hemoconcentration of the venom. Just one of the many factors already mentioned in prior posts.
Other variables include species and size of snake, Venom variations within the species, diet, geographical region of species, amount of venom injected, location of bite, depth of bite (SQ, IM or IV), number of bites, victims age and size, current health or medical history, and elapsed time since the bite.
In addition, while you are correct that copperhead venom is different than that of the cottonmouth, venom analysis of both venoms identifies many of the same enzymes in both, and copperhead venom is generally in fact lower in toxicity than that of the cottonmouth. Both venoms contain Proteolytic enzymes, Arginine ester hydrolase, Thrombin-like enzyme, collagenase, hyaluronidase, Phospholipase A2, Phosphomonoesterase, Phosphodiesterase, 5'-nucleotidase, NAD-nucleotidase, and L-amino acid oxidase. However, as already mentioned prior, copperhead bites can in fact be just as dangerous in their effects.
CroFab was initially developed for the management of mild to moderate envenomations from Copperhead, Cottonmouth and rattlesnakes, and until recently has not been tested in the management of severe envenomation. Because of it's short half-life within the body and the prolonged half-life of venom it requires the maintenance dosing, and in fact Sean Bush is currently investigating continuous infusion to avoid the peaks and vallies in effects. While you are correct that it does not contain copperhead venom and some physicians do not use it in the management of envenomation, I could probably quote just as many published medical papers that support its use to manage copperhead envenomation especially since it has shown benefit in reducing dysfigurement especially in hand envenomations. The bigger concern is the lack of efficacy in C.h. atricaudatus envenomations and their effects which many times requires massive doses or switiching to another AV if available. Such as Antivipmyn which remains currently under clinical trials.
So given the provided information of the cases and lack of specific case information, you are certainly welcome to your concerns and questions, but the validity of questioning the treatment is dubious at best since it is within the best practice of managing snakebites and is what is in the best interests of the patient. Neither of these cases involve a private keeper with a better understanding of envenomation than the general public. As a keeper, you may present with a specific treatment protocol and have the right to refuse treatment with AV under the informed consent process. However, the general public is also more likely to sue based on their knowledge base if AV is not administered.
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RE: What's up with Crofab use?
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by bwanadon on September 18, 2011
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To everyone who seems to think every Copperhead bite should immediately receive CroFab treatment the following is offered without big and medical sounding words.
1) The manufacturer has very little case study regarding its use on Copperhead bites...something like 3 cases...so, the same minimum starting dose for all bites and all vipers...one size fits all.
2) The manufacturer is in business to sell CroFab.
3) It is probable that low body weight (children) are at higher risk with any kind of poisoning.
4) CroFab and its hospital administration is very expensive unless you're one of Obama's millionaires and billionaires...Beaufort, S.C. 2008 - 12 vials and 4 days = $96,000.00
5) Bites on digits are a particular problem because the venom may remain concentrated.
6) Excessive use of CroFab in South America has been worse than in the United States; often much worse.
7) Last is a direct quote from the previous submittal, "However, the general public is also more likely to sue based on their knowledge base if AV is not administered." This is the reason for much wasted and unnecessary medical practice in the U.S. today!
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RE: What's up with Crofab use?
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by JHarrison on September 18, 2011
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Well stated Joe. Though we rarely use CroFab in severe envenomation by Agkistrodon it appears to help. As far as CroFab usage in South America I would have to see the paper on this? Working with antivenin producers I see no need for it and CroFab has been shown to have little effect on Bothrops which cause most of the bites in South America. Actually Bioclon antivenin appears to be better all around and cheaper.
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RE: What's up with Crofab use?
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by JHarrison on September 18, 2011
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Posted to soon . There are more then 3 cases studies in the usage of CroFab just here in KY. At one venom week a doctor from NC talked about 10 cases he treated with CroFab. Not sure where your getting this information but it appears very old. Also 12 vials for a Crotalus bite means it probably was not a severe envenomation.. Envenomations should be treated case by case. Also there are no Bush rich friends out there? Their all corrupt for the most part.
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RE: What's up with Crofab use?
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by AquaHerp on September 18, 2011
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I don't think that a single person here said a word about antivenom being used in every copperhead bite scenario. Nobody, doctors included, would administer AV on a prophylactic basis.
I too would be very interested to see any literature supporting the claim that CroFab is used excessively in South America. If at all.
Finally, anyone who belittles the effects of a copperhead envenomation is ignorant of the mechanics of venom and should keep as far away from venomous snakes as they possibly can.
DH
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RE: What's up with Crofab use?
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by bwanadon on September 18, 2011
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The reference wasn't to the number of cases of CroFab usage for Copperhead bites in general but to the number of trials conducted by the manufacturer for Copperhead bites.
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RE: What's up with Crofab use?
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by bwanadon on September 18, 2011
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Copperhead envenomation effects were never belittled.
Your correspondent and his wife and son have all been bitten by Copperheads and all of the bites were legitimate...none caused by handling. My 6 year old son was rushed to hospital where his condition was monitored by Magic Marker as swelling progressed and finally stopped near the top of his thigh. My wife and I endured severe pain and heavy swelling of the foot and ankle which slowly extended up to the knee in both cases. My bite was from a 2-1/2 footer. The bite itself felt no more than a very slight pinprick. Both adult bites resulted in slowly diminished amounts of debilitation for 3-4 weeks. No AV administered. My wife got a tetanus shot from our local doctor.
The real question is the current crude method of analyzing venemous snakebites and subsequent AV administration.
A likely more accurate method is available Enzyme-linked immunosorbent assay. (ELISA or EIA)
See article by Theakston on "An Objective Approach to Antivenom Therapy and Assessment of First-Aid Measures in Snakebite".
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RE: What's up with Crofab use?
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by AquaHerp on September 18, 2011
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ELISA tests can be used to detect venom in the blood. It will not accurately tell you how much, how active or what is going on biochemically within the system. We can use ELISA tests in vivo while evaluating some antivenoms and their efficacy, however, to be used as a tool to override symptomatic conditions in a human envemonation is not the answer. Nonspecific cross-reactions may take place that skew your readings and your sensitivity readings may prove out to be insufficient. There is a difference between sensitivity and specificity and false reactions and results are often a problem with relying on an ELISA test as your road map to snakebite severity or AV neutralization. Can it be used in conjunction with other methods of judging the severity and treatment? Sure. But not as a primary indicator. Teamed with platelet counts, monitoring vitals and clinical symptomatic observation, it can be useful.
To go a step further. Using an ELISA test in the lab while doing AV studies is one thing. If it's that researcher’s specialty then running these types of tests and understanding results are useful. However, to an untrained physician with no experience in this type of testing....they are simply wasting valuable time and tissue.
Many of us here, a few from which you have already heard from routinely deal with venoms from a biochemical standpoint. It's a nice cross-section of the venom realm. Joe sees snakebite on a routine basis. Jim has worked for decades extracting venoms and working closely with those creating both antivenoms and medical research. I myself have spent countless hours extracting and running about every assay and test there is concerning venom from an AV and biomedical standpoint. We are not "arguing a point" simply providing a realistic view from a professional position.
DH
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