Just Scut'n along

[Venomhunter]

Originally Posted by MDT

Trust me, I give lectures to physicians, med students, paramedics about this. I just don't get "not giving it". The ovine component reduces the antigenicity of the product SUBSTANTIALLY. Allergic rxn's are not common, and those are typically mild.

I have never seen an allergic reaction giving CroFab in all the times I have administered it. I actually had to give the Wyeth product once, immediate allergic reaction.

The ovine component sure does help alot!
The chance is always there, even with CroFab however, far less likely.
Wyeth just like L. Mactans AV (Black widow AV) can be very tricky stuff!
It's pretty interesting, why would a Black widow (Latrodectus spp.) bite trigger a allergic reaction whilst Poecilotheria spp. (Tarantula) bite doesn't? Some proteins in the venom are bigger then the proteins in tarantula venom so it's easily detected by our immune system.
That's why i always keep epinephrine and diphenhydramine in my "emergency" drawer!
It's also the case for the AV i guess, plus alot of antigens so that combined makes a risky AV.

[MDT]

Originally Posted by Venomhunter

just like L. Mactans AV (Black widow AV) can be very tricky stuff!

I actually had an honest-to-God Widow envenomation several years ago. My only one. Patient was a young pregnant woman and she brought in the spider to be identified. Black Widow for sure. Minimal symptoms, but w/ the neuromuscular stuff, she was at risk for uterine contraction and spontaneous loss of the fetus. We really deliberated on giving the anti-venom. In the end, we did not (after extensive consultation) based on the fact her symptoms were pretty mild and the risk for allergic reaction from the drug was so high. She and the baby ultimately did well.

[D Grade]

Couldn't agree more, time becomes even more crucial when an allergic reaction or anaphylactic shock come into play.

Did they find out what species of snake the bite was from?

[MDT]

No ID was made, but it really wouldn't matter. CroFab would be adequate for all players in that part of the state.

[D Grade]

Originally Posted by MDT

No ID was made, but it really wouldn't matter. CroFab would be adequate for all players in that part of the state.

Of course, I just like to know which species was the culprit.

[Venomhunter]

Originally Posted by D Grade

Of course, I just like to know which species was the culprit.

Same here!

[Venomhunter]

CroFab is a serum derived from sheep from what i've read, i don't know what animal AnaVip is derived from but if it's cheaper then CroFab and it works on more species of Crotalus (or crotalid) then i will contact an old friend if mine who works in the Antivenom distribution centre here in The Netherlands, to see if he has any plans to ship it over here.

[D Grade]

An abundance of info and great discussion, Thanks MDT and VH!

[Venomhunter]

It's getting a little bit off topic, sorry D! I think it might be a good idea to start a venom discussion thread!

[MDT]

Yes!!! Sorry D!!!! Back to originally scheduled topic!

[D Grade]

No sweat guys, this is exactly what I was hoping for.

[Aaron_S]

So in my non-medical mind I have a question, why is the new stuff cheaper? Is it due to how it's made? I would have thought that a new one would cost the same if not more if it was better, no?

Also, Matt, why did the horse serum give a reaction so quick? That ovine thing you mentioned? As I understood from your posts, doctors are hesitant to administer CroFab because they are worried about allergic reactions? I find it odd considering it could save the life and I'm wildly guessing here, that it's better to deal with the reaction than to let an envenomation go on for too long?

[Venomhunter]

Originally Posted by Aaron_S

So in my non-medical mind I have a question, why is the new stuff cheaper? Is it due to how it's made? I would have thought that a new one would cost the same if not more if it was better, no?

Also, Matt, why did the horse serum give a reaction so quick? That ovine thing you mentioned? As I understood from your posts, doctors are hesitant to administer CroFab because they are worried about allergic reactions? I find it odd considering it could save the life and I'm wildly guessing here, that it's better to deal with the reaction than to let an envenomation go on for too long?

Did some research on it, this is what i've learned about AnaVip:
It's an equine derived antiserum (derived from horses), there is no ovine component and the initial dose/additional* dose is 10 vials and the maintenance dose is 4 vials.
CroFab's initial/additional dose is 4 to 6 vials and the maintenance dose is 2 vials.
The ovine component makes it more expensive to make plus it's derived from sheep which are less frequently used.
The snake species used for the standardization are the Crotalus durissus (South American Rattlesnake) and the Bothrops asper (Fer-de-lance.)
So, CroFab is more effective because less is needed but Anavip works on more species of crotalid.
The chance of allergic reaction however is greater with non ovine serums so time will tell how this AV will do!
I'm quite curious, i hope that people with snakebites that aren't entirely covered by CroFab will get better resulrs out of this AV

*initial dose is meant to get initial control, that means that the progressive swelling stopped and blood values stay around the same value.
After this you get the patient on the maintenance dose, this is 2 vials every 6 hours, repeat this 3 times.
(CroFab)

[MDT]

Yeah, pretty much what VH said...

From an antigenicity standpoint, the Wyeth product utilized the entire antibody, and this was derived from hyperimmunizing horses. Imagine a molecule that looks like the letter "Y". That's what the molecule looks like. So this whole thing was injected and circulating in your blood stream. Your own immune system is really good at recognizing things that "don't belong", especially foreign proteins. So, upon seeing this circulating letter Y, in a lot of folks, that triggered an immune response (which manifests in wheezing, swelling, hives, hypotension, and cardiovascular collapse, which leads to you dying from anaphylaxis). This was a relatively common occurrence, but severity was variable, and clearly, was a life saving product. So you had to use it with care.

The ovine products (sheep derived) are made similarly, only that letter "Y" is chopped into pieces, for CroFab, 3 pieces (imagine cutting the Y into \, |, / ) and Anavip is carved into 2 pieces (thing of a V and | ). So they seprate and keep the "slanty" parts and get rid of the "stick" portion. Getting rid of the "stick" portion seems to significantly reduce the antigenicity of the antivenom. So, the result is a much cleaner product.

CroFab is made with 4 US pit viper species. AnaVip made with 2 SA species. I have not reviewed any pharmacokinetic data, and in full disclosure, I have not had an opportunity to use Anavip.

I do understand that the circulating level of each product is different. In my mind (again, not having read any kinetic data), it would seem that the US specific compound would be more effective in the US (each venom being genetically/molecularly different). Also, the relative cost...CroFab was the first guy out there. They can "name their price" so-to-speak. Now that there is some (apparently good) competition, CroFab will adjust prices and hopefully, everyone will be a little more sane.

As far as administering the med, that is a good question. Seriously...I don't get it. Maybe because of the reputation that the Wyeth product had? We give thrombolytics (clot busters like tPA) in the ED on a relatively common basis. This is pretty tricky stuff, in that it basically stops your ability to clot your blood. We give medications to paralyze people before we intubate them. Nothing like taking an awake, talking patient and removing all muscular control and stopping their breathing, only to insert an endotracheal tube into them and we breath for them. That is a pucker time for sure. We give all kinds of really gnarly stuff and don't bat an eye, because we know that's part of taking care of a particular disease process. So it's not like we aren't familiar with giving tricky stuff. But when it comes to antivenom, it seems like the medical community wets their collective pants.

Oh well, not sure if this answered your question, but I tried to hit the high points...

[Venomhunter]

Originally Posted by MDT

Yeah, pretty much what VH said...

From an antigenicity standpoint, the Wyeth product utilized the entire antibody, and this was derived from hyperimmunizing horses. Imagine a molecule that looks like the letter "Y". That's what the molecule looks like. So this whole thing was injected and circulating in your blood stream. Your own immune system is really good at recognizing things that "don't belong", especially foreign proteins. So, upon seeing this circulating letter Y, in a lot of folks, that triggered an immune response (which manifests in wheezing, swelling, hives, hypotension, and cardiovascular collapse, which leads to you dying from anaphylaxis). This was a relatively common occurrence, but severity was variable, and clearly, was a life saving product. So you had to use it with care.

The ovine products (sheep derived) are made similarly, only that letter "Y" is chopped into pieces, for CroFab, 3 pieces (imagine cutting the Y into \, |, / ) and Anavip is carved into 2 pieces (thing of a V and | ). So they seprate and keep the "slanty" parts and get rid of the "stick" portion. Getting rid of the "stick" portion seems to significantly reduce the antigenicity of the antivenom. So, the result is a much cleaner product.

CroFab is made with 4 US pit viper species. AnaVip made with 2 SA species. I have not reviewed any pharmacokinetic data, and in full disclosure, I have not had an opportunity to use Anavip.

I do understand that the circulating level of each product is different. In my mind (again, not having read any kinetic data), it would seem that the US specific compound would be more effective in the US (each venom being genetically/molecularly different). Also, the relative cost...CroFab was the first guy out there. They can "name their price" so-to-speak. Now that there is some (apparently good) competition, CroFab will adjust prices and hopefully, everyone will be a little more sane.

As far as administering the med, that is a good question. Seriously...I don't get it. Maybe because of the reputation that the Wyeth product had? We give thrombolytics (clot busters like tPA) in the ED on a relatively common basis. This is pretty tricky stuff, in that it basically stops your ability to clot your blood. We give medications to paralyze people before we intubate them. Nothing like taking an awake, talking patient and removing all muscular control and stopping their breathing, only to insert an endotracheal tube into them and we breath for them. That is a pucker time for sure. We give all kinds of really gnarly stuff and don't bat an eye, because we know that's part of taking care of a particular disease process. So it's not like we aren't familiar with giving tricky stuff. But when it comes to antivenom, it seems like the medical community wets their collective pants.

Oh well, not sure if this answered your question, but I tried to hit the high points...

Great explanation MDT!