It’s a good drug, it’s a very effective drug, and I know, red devil, strongest drug. On the off chance that you begin Googling, you can actually presumably crack yourself out about doxorubicin. Hello, everybody, today I am going to give you seven things that you have to think about the chemotherapy drug doxorubicin. Why am I picking doxorubicin? Because it is one of the most commonly used chemotherapy drugs in dogs and cats, and it also has quite a reputation. If you start Googling it, and I know, come on, we all Google, it literally is known as one of the strongest chemotherapy drugs in people, and it is also AKA the red devil. So that’s a lot to worry about if you have been told that your dog is going to get doxorubicin either in a multi-drug combination chemotherapy protocol, or sometimes it’ll be the only drug that’s going to be used for your dog’s chemotherapy. So let’s unpack it, let’s break it down. Let’s go through the seven things that I want you to know about doxorubicin chemotherapy for dogs and cats. So the first thing that we’re gonna talk about with doxorubicin is when do we give it and how do we give it. So the common cancers that it’s prescribed for, the most common is going to be for dog lymphoma and cat lymphoma. For dog lymphoma, it’s commonly used in the CHOP multi-agent chemotherapy protocols. And guys, you know what I’m gonna direct you to do. If you have questions about lymphoma, check out my chemotherapy playlist and check out my article on the different chemotherapy protocols. Some of the time for hounds with lymphoma, we will utilize single operator doxorubicin. Also another common cancer that we will use it for in dogs is for hemangiosarcoma and, of course, in the third article of my hemangiosarcoma series, we talk all about doxorubicin, that that is the drug of choice. For cats, again we will use it in the lymphoma multi-agent chemotherapy protocol, but not a very good single agent protocol for kitty cats. We also use this for lots of carcinomas, so for mammary cancers and sarcomas as well. So again, it is a very commonly prescribed chemotherapy drug.
How do we give it?
We cannot give it orally, does not come in a pill form. It is going to be given injectable, IV. Many of the other IV drugs are given more quickly, as what we call a quick IV bolus. Doxorubicin needs to be given as a slow IV infusion, usually diluted in fluids. So in cats, it’s usually given over about 15 to 20 minutes, and in dogs, especially larger dogs, it’s going to be given over about 30, for bigger dogs even could be over 40 minutes, and it’s gonna be given in usually about 100 mLs of fluid. So it’s going to be given as a moderate mixture and we’re going to give you a few mutts getting their infusion as well. And you can watch some of my other articles, but dogs are gonna come in. I’m gonna do a physical exam. We’re always gonna check some blood work to make sure their white blood cell count is okay, and then they’re gonna go back into our nice, quiet, secluded chemotherapy room. Big dogs, we usually are gonna do their chemotherapy on the floor. Cats and small dogs are likely gonna be done on the table with an experienced chemotherapy nurse. And what’s really important about these technicians is they have a lot of experience giving a drug like doxorubicin. And one of the reasons that’s so important is you don’t want doxorubicin to get outside the vein. So if it does get outside the vein, that’s something called extravasation, and it can cause a significant amount of tissue damage. So one of the reasons you want that experienced oncology veterinary technician is they’re used to placing these catheters while making sure it’s what we call a good stick, they’re getting good blood return, because again you don’t want any of the chemotherapy to go outside the vein because it can cause significant damage, and I mean sloughing and just a big mess. I’ve been an oncologist now for about 20 years and I’m fortunate enough to say that we’ve never had a doxorubicin extravasation, and so I’m really proud to say that, but they do occur.
It’s something that, again, you wanna be super careful with. So again, it’s given as an intravenous injection, a slow infusion. So that means that your dog’s gonna be there for a little bit, so usually in my practice, by the time they come in, we run blood work, and we give the chemotherapy, they’re there at least an hour. Big dogs maybe an hour to an hour and a half. Because doxorubicin is a strong drug, as I talked about in the introduction, we are gonna do some things at the time of treatment, so what I call some pre-treatment, and things are gonna be a little bit different in dogs and cats. If you have a dog, we are gonna give two pre-treatment injections at the time of doxorubicin treatment. For dogs, we’re gonna give an antihistamine, we’re gonna give Benadryl right before we give the doxorubicin because doxorubicin can cause histamine release, so they can have an allergic-like reaction. We don’t see that in cats, so they don’t get that. One thing that is similar in dogs and cats is both of them I will give CERENIA injectable to prevent any nausea and vomiting, and that will last 24 hours.
So again, dogs will get Benadryl and CERENIA injectable, and cats will just get injectable CERENIA. Little tip in the event that you wanna set aside some cash, particularly in the event that you have a major canine, ‘cause injectable CERENIA can add up, especially in big dogs, is you can ask your oncologist or your veterinarian if you can give oral CERENIA instead of the injectable CERENIA. Over time, with multiple treatments, that will save money. But hey, if you forget to give the oral CERENIA one time before the doxorubicin, please let me know and we will give injectable that day because it’s really important that we do pre-treat to prevent any nausea or vomiting because again, remember, doxorubicin is one of the strongest drugs in the protocol. And as I’ve talked about in many of my other articles, it is very important to take a preventative approach with gastrointestinal side effects, so we want to prevent nausea and vomiting rather than wait for them to happen. So I’m gonna direct you also to article number 93, where I spend a lot of time talking about the different side effects of chemotherapy, especially the gastrointestinal side effects. The third thing to know about doxorubicin is that we want to carry that philosophy of preventing side effects after. So this is where you are gonna help us help your dog. So for dogs, there are really good studies that show if we give oral CERENIA after the doxorubicin, that has been shown to help prevent vomiting and diarrhea as well. So they day after your canine gets doxorubicin, I will educate you to begin CERENIA for about four to five days automatically, even if they’re eating and no nausea and they’re feeling super fantastic. We are always going to give oral CERENIA automatically as a preventative ’cause like I just mentioned, it’s much better to be preventative than to wait for side effects to happen and then try to treat it. In cats, they tend to tolerate chemotherapy better than dogs, so you’re gonna go home with CERENIA, but I don’t automatically have you start the oral CERENIA. I’m going that injectable CERENIA with the doxorubicin, but you don’t automatically have to give the CERENIA. If you are starting to notice that your cat is picky or you do notice vomiting, we will have you give the CERENIA. Again, check out article number 93 for more information about the side effects after chemotherapy. Another reason why doxorubicin has such a reputation for being such a strong chemotherapy, it is a drug that is highly likely to be myelosuppressive. That’s a really big word. What does that word mean? It is likely to cause a low white blood cell count. Specifically, the cells called the neutrophils, which are the injection-fighting white blood cells. And again, I talk about these in much more detail in article number 93, so definitely check that out if you’re looking for more information. But how does that relate to doxorubicin? So this is a drug that I expect many dogs and even cats to potentially get a low white blood cell count. So the first time that your dog gets this drug,
I personally do send dogs home preventative antibiotics, and I have you start that three days later to cover them during that window when your dog may potentially get a low white blood cell count, which is seven days after the chemotherapy is given. And I am gonna have you come back on that seventh day so we can check a CBC, a complete blood count, to look to see if those white blood cells, the neutrophils got low. That low is called a nadir, and so you’ll often hear that appointment we’re gonna have you come in to check the nadir CBC to see if your dog has gotten low. If they do get low, the reason we wanna know that, if they get super super low, they are at risk for sepsis or an infection. And again, I do go into this in much more detail in article number 93. The reason this is important for doxorubicin, again, we sort of grade drugs on their likelihood of causing this low white blood cell count. So vincristine, another drug in the lymphoma protocol, is not very likely to cause a low white blood cell count, but doxorubicin is. So again, that’s why I’m gonna take that preventative approach with antibiotics. But guys, I can only tell you how I do things. Not every oncologist will use preventative antibiotics or have you come in for that nadir CBC. So I’m just letting you know how I do things, but it’s great to just check in with your oncologist and with your veterinarian and say, “Hey, do we need antibiotics? “What’s your philosophy on how do you do things “after a strong drug like doxorubicin?” Cats, they can get the low white platelet tally, yet once more, they normally will in general endure chemotherapy a little bit better than dogs. All right, guys, number five. The fifth thing that I want you to know about doxorubicin is it has a unique toxicity called cardiotoxicity, or heart toxicity. And this is actually something that we see in dogs and not cats. So again, you’ll hear me say that cats are not small dogs, and this is where that is definitely, there’s differences between dogs and cats. So doxorubicin with multiple dosages can cause cardiotoxicity.
And that is usually shown in dogs that are getting full dose doxorubicin after about six to eight dosages of doxorubicin. And that doesn’t have to be given together. You can get four now and four later. It’s cumulative lifetime dosages. Most oncologists will max out at six dosages of doxorubicin. I know some at five. But I will only give six doses of doxorubicin. So a good example is in the lymphoma protocol. The first time through, a dog will get four doses of doxorubicin. If and when they relapse and they’re going through the protocol again, we will only give them two more doses of doxorubicin, and then we will switch out to a similar anthracycline, which is the type of drug that doxorubicin, but a little bit more heart friendly. So again, that is a unique side effect to doxorubicin. It’s not very common. I have rarely seen it in dogs that have gotten less than six dosages, maybe one or two. I have seen it in one dog that was treated elsewhere, not by me, by another oncologist, that got nine dosages, but again, super super uncommon. So again it’s just something to be aware of. In my opinion, doxorubicin is such a great effective chemotherapy drug. It’s not a reason not to give it, so that’s a double negative. I still would use doxorubicin, but again, we just have to take precautions. What precautions can we take? So before we give doxorubicin the first time, we can do some tests to see what’s going on with the heart. None of these tests will predict whether or not your dog will have cardiotoxicity, but usually what I will do is either an EKG or an ECG or rhythm strip to see if they’re having any VPCs, abnormal arrhythmias, or what I really like to do is something called a fractional shortening, which is done with the ultrasound probe to see how effectively the heart is contracting. The heart damage that it causes is to the muscle, and it affects the ability of the heart muscle to contract, with is called the fractional shortening. So the toxicity causes a decrease in the effectiveness of the heart pumping, so it decreases that fractional shortening. So I do like to get a baseline of that fractional shortening of the dogs to see that it’s okay. An EKG is another common test that many oncologists will check before the baseline. So again, your oncologist may recommend an ECG or a fractional shortening done with an echo probe, an ultrasound probe, or a full echocardiogram. For me, the dogs that I’m gonna recommend a full echocardiogram are gonna be dogs that are high risk for this heart muscle change, decreased fractional shortening, which are usually Boxers and Dobys. So those are the dogs that I’m gonna have go see the cardiologist before I give doxorubicin.
What about cats?
So I mentioned that we don’t see this cardiotoxicity in cats, so we don’t have to worry about it. No ECGs, no echocardiograms before they can get doxorubicin, and they can get more than six doses of doxorubicin. But one of the things that’s unique in kitty cats is doxorubicin can worsen kidney disease. So if I have a kitty cat that has pre-existing kidney disease, I’m gonna watch those kidney values very closely. So on the blood work, we’re gonna be checking the BUN, the creatinine, the concentration, the urine specific gravity, and things like that. If they have mild pre-existing kidney disease, again, can’t make specific recommendations about your kitty, but usually we can still use doxorubicin safely, just monitoring those kidney values. If I have a cat with really severe kidney failure, I would be very cautious about using doxorubicin. And the last thing that I want you to know is, I’ve told you all these sort of scary things about doxorubicin. Guys, it’s a good drug. It’s a very effective drug, and I know, red devil, strongest drug. On the off chance that you begin Googling, you can actually presumably crack yourself out about doxorubicin. And what I find really interesting, especially in the combination chemotherapy protocols, especially for dogs going through lymphoma treatment, by the time a dog gets doxorubicin, they have seen vincristine, they have seen cyclophosphamide, maybe Elspar, and so it’s the last drug that they’re getting in the protocol, and I warn families this is the strongest drug in the protocol. We’re gonna take this preventative approach. We’re gonna give CERENIA. Your dog’s gonna get Benadryl. The Benadryl may make them tired for 12 to 24 hours. Gonna start the CERENIA tomorrow. A couple days, you’re gonna start the antibiotics. I’ll see you back in a week or you’ll go to your vet to check the white blood cell count. But this could be, they could still get diarrhea, but this is the strongest drug. But for lymphoma, it’s the drug that really makes a very positive impact in the response rates and the survival times. I can’t tell you how many owners say, “Yup, that was the easiest drug in the protocol “and, nope, we didn’t have any side effects.” So we take the preventative approach. I’m very proactive with nausea medications, but I want you to know, it’s very well tolerated by many dogs and many cats. So it’s a good drug. If your pet was recommended it, I think it’s worth considering. I hope this article helped. Thank you so much for Reading, guys. I hope this one was helpful. Is there another chemotherapy drug that you would like to know about? Thank you so much for Reading. Have a good one,