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Featuring Demian Dressler, DVM and Sue Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

Urinary Problems And Cyclophosphamide

Updated: November 14th, 2018

One of the most common chemotherapy drugs used today is cyclophosphamide.

This medication can be given at home, as it comes as a pill that is given by mouth.  It can also be given as an injection in the veterinary hospital.

One of the side effects that is seen in about 1 in 10 dogs on this drug involves the bladder.  The signs you will see if your dog is experiencing this side effect include:

  • urinating small amounts frequently
  • straining to urinate
  • posturing for a long time with little urine being produced
  • blood in the urine
  • having to go outside more frequently to urinate

These are all signs of bladder inflammation.  When the bladder gets inflamed, our dogs feel like they need to go urinate more often.  They also feel like they need to empty their bladder more, even when they have passed all the urine they have and their bladder is empty.

We make these assumptions about how they feel since this is what people experience when we have bladder inflammation, which happens with problems like bladder infection.

The reason a dog might get an inflamed bladder while taking cyclophosphamide is this drug can cause a condition called sterile hemorrhagic cystitis (SHC). This can be translated to mean “an inflamed bladder that bleeds without an infection.”

The reason this can happen is that dogs on the drug accumulate a by-product in their bladder called acrolein.  This chemical is produced in the body when cyclophosphamide is broken down, and it collects in the urine.

Oncologists will often combine cyclophosphamide with medications like prednisone or prednisolone, which can decrease the odds of SHC. If diuretics are administered when the drug is given in the hospital, it can also lower the risks.

It is important to differentiate SHC from an actual bladder infection, which is also common in dogs with cancer receiving chemo. The signs you see with a bladder infection are identical to SHC, but antibiotics are used to treat an infection.  They will do nothing for SHC however, which requires different steps.

So it is important to get your dog’s urine tested if you see these signs to find out if infection or SHC is the real culprit.

The Dog Cancer Survival Guide has a lot of information on how you can address possible side effects from chemotherapy in your dog if you would like more on important topics like this.


Dr D

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  2. Wendy on June 26, 2014 at 3:50 pm

    My dog was recently experiencing trouble urinating and I noticed some blood. I took him in and the full battery of tests were run on both his blood and urine. The culture came back clear and we also had an ultrasound performed, so our Dr. suspects that he has developed SHC. He stopped taking the cyclophosphamide portion of his chemo regime about three months ago, but it seems he developed it anyway. The Dr. only stopped it after another oncologist he saw seemed surprised he was still on it. The Dr. wanted to put him on Rimadyl, but we told her we thought that we couldn’t do Palladia and Rimadyl simultaneously? She agreed. The Dr. has now suspended the Palladia portion of his chemo and put him on Rimadyl to reduce the inflammation in his bladder. My concern is what will the cessation of the Palladia likely do, since he has been doing so well? I read on the dogcancerblog that some dogs take Palladia and Rimadyl simultaneously, so now I’m really confused. What is your opinion? Other than this setback, he’s been doing really good.


    Don & Wendy

  3. Chuck Engels on September 27, 2010 at 6:12 pm

    Dr Dressler,

    My 13 yr old Shepard/Retriver mix has been undergoing therapy for Multiple Myeloma for about 2 years now. Until recently, this had been well controlled with Melphelan, but it has finally caused bone marrow suppression in her and we are switching to a pulse treatment of Cyclophosphamide. I read your recommendation to supplement with Indole-3-Carbinole as a buffer against bone marrow toxicity from the Cytoxan. In online research, I read that the real effector is DIM which is created by conversion of the I3C in the stomach. The question is, should I be supplementing with I3C or the DIM since there may be more side effects from the I3C than the DIM?

  4. Sherry on August 8, 2010 at 5:20 pm

    Back in April our 6 year old mini schnauzer was diagnosed with a likely meningioma. She was showing signs of lethargy. She wouldn’t eat. After running every test imaginable a vet specialist said she highly supects a meningioma but without an MRI she couldn’t confirm it. She said depending on how fast it progresses we are looking at 3-6 months. Thankfully we have had 4 months with her. Right now she is sleeping more. She wants to be under my desk all day. If my husband comes home from work she will come out to see him and comes back instantly. There are times she won’t even come out to go to outside. She wants to lick alot and rub on her face with her paws and up against things. She acts like she is depressed. Any feedback???

  5. DemianDressler on July 22, 2010 at 10:57 am

    Dear Nicole,
    Yes, you are correct, and yes, Lasix is the most common diuretic used.
    Thanks for your input!
    Dr D

  6. Nicole Thome on July 18, 2010 at 5:28 am

    Hi Dr. Dressler,
    Isn’t it true that prednisone and NSAIDs shouldn’t be mixed? Therefore if a dog is on metronomic protocol with cyclophosphamide (cytoxan) and an NSAID, prednisone is generally not in the regime.

    Lasix is another answer to combating urinary problems with dogs on cyclophosphamide.


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