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Pet Rats/Older sick rat with abcessed tumor


QUESTION: Hello Debbie,

I have had 7 rats these past 3 years, and sadly to say they have all passed tragically. My current situation is with my oldest female Cookie, she is the mother of 3 that I had (2 passed already) and may I add she has had a great life living 3 years this winter. She has a mammary tumor that abcessed a few weeks ago. There was necrotic tissue hanging, exposing a lot of yellow pus, so I removed it. I had been cleaning the pus out with normal saline daily also and placed her on antibiotics; amoxicillin for the wound. She has recently stopped eating and she is breathing very hard. Knowing rats and their respiratory illnesses I started her on doxycycline right away, so she is receiving both twice a day. I am scared nothing is helping her, she is sluggish, poor to no appetite and also has a dark blueish tinge to her both hind legs. She is having a lot of trouble getting around also. The only good thing is that she is taking ensure up to 4 times a day. I work as a nurse and can see that she may have symptoms of chf due to being an older rat. I also believe she is in pain from the tumor/ abcess, on her left side. I am scared to touch it and am currently applying triple antibiotic ointment. I am going to make an appointment with my vet tomorrow who specializes in rats. Her lungs also, sound clear but respiratory rate is very high and I have been giving her some leftover Metacam prescribed to one of my other sick rats. I am just curious and wanted to ask what you think the best possible outcome may be for cookie. I don't want her to suffer, and was thinking we could treat whatever is wrong. Euthanasia would be my last resort; as I just put one down last week who had a massive tumor wrapped around her bladder and was no longer enjoying life anymore......thank you for you expertise ahead of time!!!

ANSWER: Hi Shannon,
I'm sorry your old girl has problems. It could be her mammary tumor is malignant. Can you send me a piture? Tamoxifen can work well to shrink malignant mammary tumors.

Yes, CHF is likely, so you want to ask your vet for enalapril at 0.25 mg/lb (0.55 mg/kg) twice a day. If it's going to help, you should see improvement in her color and breathing within 2 days. See the article about Respiratory & Heart Disease on my website at

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Cookies tumor
Cookies tumor  
QUESTION: Here is cookies tumor Debbie, what you said about it being malignant makes sense.  When I take her to the vet, I will ask for enalipril. I hope this will help and perhaps tamoxifen too, i'm not sure what the vet will stay in regard to her age and tamoxifen use.  As I have seen it used an elderly human being so I don't think it will cause her any harm. Thank you for your expertise once again I will let you know what happens at the vet!!  Also, can an extreme amount of pain cause a rat to act in this way, not eating or drinking?

Shannon 🐭

It looks malignant, but doesn't look like a mammary tumor. However, tamoxifen might help for other types of tumors as well. See this article

Yes, pain can affect appetite, but other things can too. A bacterial infection for one. You can give her two or 3 times the normal dose of amoxicillin. Normal is 10 mg/lb twice a day, so you could try 20 or 30 mg/lb.  CHF can affect appetite too.  You could try giving her acetaminophen for pain at 90-140 mg/lb every 4-12 hours. I don't recommend an NSAID with an open wound because of the risk of bleeding.

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Debbie Ducommun


I can answer any questions about pet rats, but you will probably be able find answers to simple questions more quickly on my website at If you have a life-threatening emergency you can try calling me at 530-899-0605. I am not usually on the computer on the weekend.


I have been "The Rat Lady" since 1985 and am recognized as one of the world's experts on pet rats. I have 3 published books and already answer lots of questions about rats daily.

President of Rat Assistance & Teaching Society

I am a monthly columnist for Pet Business magazine, and my writing has appeared in other magazines. I have 3 published books.

BA in Animal Behavior

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