Bear Man may be starting Darbepoietin - advice?

Bear's hematocrit has dropped to .19, which is the number at which my vet suggested starting Aranesp shots. Reticulocytes are 0.5 (ref 0.4 - 1.4). RBC 4.5 (ref 6.0 - 11.0) and Hemoglobin 57 (ref 80 - 150). His hematocrit on June 24 was .23, and 3 weeks prior to that was .21.

I have been speaking to the pharmacist at the hospital where I will be buying the medication. I have some concerns about accurately dosing it. The darbepoietin comes in single use pre-filled syringes containing 10 mcg. The needle is not removable, and the syringe has no markings on it. Bear's dose is 6.25 mcg. You would have to discard by eyeball the excess 3.75 mcg. You could try transferring the contents into a sterile vaccuum container, but the darbe has no preservatives in it, and every time you transfer the contents, you have a high risk of losing sterility. The syringes are $150 (plus taxes) for a package of four. This is child's play compared to the question of dosing the alternative drug, Eprex, according to the pharmacist, and the info she gave me regarding the formulations it comes in here in Canada. Also, the type of darbepoietin available in Canada is the type (containing polysorbate 80) that carries higher risk of causing an antibody reaction.

Does anyone have any experience purchasing and administering this drug? I don't think that my vet has much, or any, experience using it in her practice.

 

Have you looked into the possibility of ordering it from the US? It comes in multidose vials here.

Actually, that's theoretically probably the better type. There are two types -- one with albumin and one with polysorbate. Albumin is a blood component and theoretically could have some potential for antigenicity. In practice they are interchangeable and none of the internists that use it frequently have voiced any concern about either one.

 

I have not looked into that, as I know that packages from the US usually are delayed going through customs, and I have concerns about keeping the product refrigerated properly in transit.

 

Yipes, I just looked at US pharmacies that shipped to Canada and they charge a fortune so nevermind.

How much does Bear Man weigh (kgs)?

 

He weighs 3.96 kg today.

At the vet his heart rate was still racing at 264, despite the fact that his thyroid has normalized. At home today, it seems to be around 200.

 

This was while he was relaxed, just lying around? If so it may be a sign of anemia; his body is trying to compensate by increasing cardiac output. This can lead to heart problems, so treatment of the anemia should take place sooner rather than later (I'm saying that as a general statement, I know you are working on things for your cat as we speak).

I don't know if you can follow this link: http://74.6.239.67/search/cache?ei=UTF- ... E79rgFSg-- If not, you can just google western veterinary conference updates chronic kidney disease and look for an article by Larry Adams. He gives a darbe dose which I've read before, of the EPO dose divided by 200. This ends up being close to 0.45mcg/kg, another dose I've heard before. This wouldn't help you with your syringe problem except to say that you could use the same syringe twice or even three times, getting multiple doses out of it.

 

Yes, the heart rate today was just while he was lying around (which is all he does). At the vet he was very agitated.

Tanya's site gives several different dosage protocols for Aranesp: http://www.felinecrf.org/erythropoietin ... ning_rhepo
1) .45 mcg/kg (For Bear = 1.8 mcg)
2) .25 - .5 mcg/kg (For Bear = 1.0 to 2 mcg)
3) 6.25 mcg regardless of weight
4) 5 mcg

5) And then there is the option in the link you provided (thank you). I am not sure that I follow the calculations, but you are saying .45 mcg per kg? Or .45 mcg per Bear?

My vet seems to have found option 3 on her vin network. It's a bit disturbing that there is so much variance, given the potential for a deadly antibody reaction. Is it better to start low and go slow?

Do you think that using the syringe more than once would compromise the sterility of the contents (there is no preservative)? I am also doubtful that I could accurately control the plunger to deliver only a portion of the contents.

 

((((Linda and Bear))))
Am sending prayers and snowflakes.

 

The calculation is this: calculate the dose for EPO, so 75-100U per kg (297-396 for bear), then dived that by 200 to get the dose in mcg/kg for darbepoetin. This would be 1.48-1.98 mcg for Bear.

VIN has the 0.45mcg/kg, the 6.25mcg, and the EPO-to-darbepoetin options. One of the main nephrologists on VIN uses the first option, and the last was presented in 2009 by a specialist at a vet conference. The antibody reaction can occur with any amount, so it's not about that. There is no "start low" policy, but I don't see the harm in starting at a lower dose (for financial reasons, and for ease of administration).

You create some theoretical risk by using the syringe more than once, but honestly a lot of things don't have preservatives and we use them multiple times anyway, like the potassium we add to fluid bags, and the fluid bags themselves. The longer you go between uses, the higher the chance of creating issues. Human medicine is all about single-use stuff so any human doctor or pharmacist will strongly adhere to that policy.

(If you do end up doing this, you can 'flush' the needle by pushing through a small amount of liquid before you do the next injection.)

If you feel it would complicate things, you can just follow the pharmacist's plan and push some of the product out of the syringe before giving the rest of the injection. Knowing the wider dose range, though, means that you dont' need to feel like you must be very exact. As long as you get rid of 1/3 of the contents you shouldn't 'over-dose' according to the guidelines.

 

If you didn't see Carolyn's response on the Feline Anemia list, look for that. There are two dosing protocols used, and people on that list (and a few others I'm a member of) have had good success with the human dosing protocol for patients with kidney disease -- sized down to a cat dose, of course. Use the most conservative dose you can, as people on the higher dose protocol have seen HUGE jumps in PCV, which can lead to stroke because the blood thickens up too quickly. A little of this stuff goes a long way. Better to go low and slow and increase if need be than floor it and end up with a problem. I hope you see more responses on the anemia list. It is kind of slow sometimes but hopefully more people will chime in.

 

Jess,
According to your link, is it the weekly dose of rh-EPO divided by 200?
i.e.
(75 - 100) X 3 = 225 - 300
Multiplied by 3.96 for Bear = 891 - 1188
Divide by 200 = 4.46 - 5.94 for Bear ??

Thanks again.

 

Yes, sorry, you're right. I thought something was funny when I wrote it, actually, but didn't know what it was, I'm glad you caught it.

What did you decide to do? Have you started yet?

 

I spoke to Bear's regular vet today. She has been off recovering from surgery, and returned today. She wants to start with the 6.25 mcg dose. She cites Dr. Alice Wolf, for one, in support of this dose. We will order the 10 mcg syringes that are available here (the type containing polysorbate 80), inject the contents into a vaccutainer, and then draw out the correct dose. She will give one shot of iron dextrans with the first darbe shot. Once the iron and the darbe are in stock, I will take Bear for a recheck of PCV and BP, and the vet will measure out and administer the darbe shot. The plan is to give the shots (checking PCV and BP before each shot) weekly until PCV rises to .30 - .35, and then reduce the frequency of shots to every 2.5 - 3 weeks.

Thank you so much for your help, Jess. I will keep you updated.

 

Linda,

have not been around much and just catching this now.

No advise. Just wanted to send good wishes for Bear and hope that you can get his counts up.
I hope you will update soon.

(((((((((( Linda ))))))))) and scritches for Bear Man . and Teddy too of course.