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Diarrhea resolves with Cephalexin.

Species: Dog
Breed: terrier mix
Age: 8-11 years
Dear Dr. Marie,

I’ve been in the throes of a medical mystery with my beloved dog, Cori. Any intuitions or thoughts would be more than appreciated.

About four years ago Cori, my 65-pound white terrier mix, then 6 years old, came down with a fungal skin infection that produced pustules chiefly along her stomach. At first my veterinarian recommended just a medicated shampoo, Sebezole, twice a week, for a month. The blisters could not be maintained without the shampoo and eventually began enlarging – sometimes the size of a walnut. Cephalexin, 500 mg, twice a day, was prescribed.

For a year and a half we struggled with a regimen of Cephalaxin, on and off, Sebezole baths twice a week and eventually some sort of injection that was expensive and used just twice. Eventually the blisters healed!

However she began showing bouts of watery diarrhea that would last weeks and could not be controlled without metronidazole. She had no fever, no loss of appetite and no vomiting. Additionally we tested for parasites and did two rounds of Panacur to make sure.

Metronidazole became a life saver. After about every 9 pills (1 and 1/2 twice a day, 3 days), her digestive system would stabilize for a week to two weeks. After about two years of this she began straining to urinate multiple times throughout every walk. Blood work showed only mild liver dysfunction and no UTI. The veterinarian believed her stomach was slightly tenser than it should be. The long-term use of metronidazole was suspected as the culprit and I was told there was no alternative.

After some persistence and experimenting I discovered a certain high quality probiotic that worked wonders for about two months before the relentless diarrhea returned. Pepto-Bismol, to coat the stomach, doesn’t really help at all. Loperamide only helps moderately, and appears to produce some discomfort for her every time – after taking it, she will often refuse to eat for a day or two, when otherwise her appetite is excellent. And the benefits of the Loperamide appear to diminish over time.

I struggled with this routine of probiotic, Loperamide and Pepto until the skin infection returned recently. It was a very mild outbreak and Cephalexin cleared it completely.

But to my surprise, the Cephalexin completely fixed her digestive issues too. While on the 14 day prescription, every stool sample was completely normal. After finishing the prescription about a week ago, the severe diarrhea returned today.

Is there some connection the veterinarians I’ve consulted don’t understand? Could there be a bacterial infection in the intestines that somehow responds to the Cephalexin? My veterinarian said I could try another round of the Cephalexin to see if the results return or even last – does this make sense? If the long-term Cephalexin from those years ago simply irreparably damaged the balance of the flora in the colon and intestines, why would using the Cephalexin now produce completely normal stools for a short period of time?

I’ve consulted everyone I can on a local scope.

Thank you for taking the time to read about us.

Kind regards,

Richard and Cori


Online vet, Dr. Marie

Dr. Marie replied:

Hi Richard. It sounds like you and Cori have been through so much! I do have some ideas for you though.

I'm wondering if Cori may have something called SIBO which stands for small intestinal bacterial overgrowth. We often don't know the cause of this condition but dogs can have very serious and usually chronic issues with diarrhea.

Cephalexin is not an antibiotic that we would normally use to treat SIBO, but it's possible that it helped somewhat. Metronidazole probably would help, but it is not a drug that we like to use long term.

You may want to ask your vet about the possibility of using a drug called Tylosin. It is kind of an old school treatment, but I have found it to be a wonder drug for many of my patients with chronic diarrhea. We buy it in a powdered formulation that is meant for use in chickens. Then, for a dog Cori's size we would administer 1/8tsp either once or twice daily in the food. Many of my patients need to be on it all of the time although I do have some that can have several weeks off of medication and do well. There are no known side effects of long term use of Tylosin. However, it does have a bit of a yucky taste. I have found that little dogs really don't like it but usually the medium to large breed dogs eat enough food that the tylosin is disguised enough for them to eat it.

There is a possibility that the diarrhea is caused by some type of inflammatory bowel disease or even a condition called lymphangectasia. It is possible that there is some SIBO (small intestinal bacterial overgrowth) secondary to that condition and this is why the antibiotics helped. If this is the case then the diarrhea will eventually come back again. Ideally, it would be very helpful to have biopsies done to determine if there is IBD or lymphangectasia. This can be pricey though and does involve either a surgery or use of an endoscope under an anesthetic.

If this were my case, and you were not willing to do biopsies I might consider use of steroids. I would likely prescribe prednisone and taper the dose down to see what the lowest effective dose is. Many dogs with forms of IBD can be controlled on very low doses of prednisone.

I think that the plan to continue with a longer course of Cephalexin is a good one as it seems to be working. You'd hate to get an infection *almost* cleared up and then stop and there is no harm in treating Cori for longer.

I hope that this has been helpful. Please let me know if you have more questions.

Dr. Marie.



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Disclaimer: Although Dr. Marie is a qualified veterinarian, the information found on this site is not meant to replace the advice of your own veterinarian. AskAVetQuestion.com and Dr. Marie do not accept any responsibility for any loss, damage, injury, death, or disease which may arise from reliance on information contained on this site. Do not use information found on this site for diagnosing or treating your pet. Anything you read here is for information only.

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Dr. MarieDr. Marie is a veterinarian who practices in a busy animal hospital in Ottawa, Ontario. She created Ask A Vet Question as a resource for good, accurate veterinary advice online. Dr. Marie treats dogs, cats, hamsters, guinea pigs, and rats. She has been a vet since 1999.

Is an online vet visit just as good as a trip to your veterinarian? No! But, many times, asking an online veterinarian a question can help save you money. While Dr. Marie can't officially diagnose your pet or prescribe medications, she can often advise you on whether a vet visit is necessary. You can also ask Dr. Marie for a second opinion on your pet's condition.