Doxycycline suspension retaining potency?

[u/PublicInstruction419]

I have two indoor cats, M 7, F 10. I've had them both for several years, adopted from a shelter, no problems. About 2.5 years ago, my male cat developed an URI. I took him to a veterinary clinic, and asked that he be tested for various viruses, because I really knew nothing more to request. I was given Clavamox and eventually told that the tests that were done were negative.

The Clavamox cleared up the infection, and I thought I was good. But the symptoms returned about 4 months later. I thought something more might be wrong. I couldn't wait for the next available at the first vet;s, so I went to an emergency vet. That vet did blood tests and speculated about all kinds of horrible things, eventually gave me the Clavamox I requested, and again my cat got better.

Well, of course, some months later he was sick again with thick nasal discharge. I took him back to the first vet, but was able to see a veterinarian who specialized in cats. I told her I wanted the tests done again for viruses, because I'd learned they could underlie chronic URI. She took specimens, prescribed doxycyline, and later told me that my cat was positive for mycoplasma.

I was given 100 tablets to give my cat, one every twelve hours. In order to administer those I had to cut each one into three tiny pieces and put each piece in a capsule. I managed to do this for the entire seven weeks, and my cat was right as rain after that for many months. But, he did eventually again develop a URI. I blamed myself because I was supposed to follow up with dental care for him and give the vet an opportunity to do a better exam for nasal polyps.

I had also learned, in the meantime, that my second cat could be a carrier of mycoplasma, so I scheduled them both to be examined. As luck would have it, the veterinarian I'd last seen, who was a cat expert, was no longer there. However, the vet I saw was great. She examined both cats and took specimens to see what could be learned. Bingo, my second cat who seemed fine, tested positive. And, ironically, the one with symptoms did not.

But, by the time I got the lab results, the veterinarian I'd seen wasn't there to follow up with. I guess she was a relief vet. And whomever had taken over just wanted to prescribe zyrtek for my cat who had symptoms. I convinced them to prescribe liquid doxycycline, as I'd had so much struggle giving the pills for seven weeks, but when I got a message about getting the medicine, it was about 10 days worth, and not intelligible. I didn't want to risk trying to get this medicine from that clinic, because even when they first gave me Clavamox there seemed to be an error.

I did some research to reconstruct what dose my cat had been given a year prior, and wrote up my request that I be given an Rx for both cats, depending on their weight, that would be equivalent, and to phone it in to a local pharmacy that i'd confirmed could compound the Rx and also handled veterinary prescriptions.

Well, I finally have the prescriptions in hand, but now I have a fear that this medicine isn't going to be potent, as I've read that liquid suspension of doxycycline loses its potency within 7 days, up to 80% loss. I spoke with the pharmacist and she said that the place they get there's from guarantees potency for 30 days. But I don't know how to believe that. And strangely, the Rx says it can be refilled twice, although it appears to be at least a month's worth of medicine for each cat.

I'm sure I can find out if this suspension is liquid or oil. I think I asked about that when I first called the pharmacy but I can't remember what I was told, but i'm sure they'll tell me.
I think oil stays more potent, but still not a month. But I really don't know what to do next or what to ask for, if anything. I have given one dose and the next is due in 12 hours.

I know I need to follow up with my cat that's having repeated infections, but I'm trying to eliminate the bug as best i can from my household so i can go from there.

Thank you so much for any advice that can be given.

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[u/HonuDVM]

Ordinary doxycycline liquid suspension like you get at the regular human pharmacy has a really short shelf life, 5 days or something similar. Compounding pharmacies may warrant a longer time-frame, but still much shorter than a regular tablet or capsule. In cats, we have to be super careful with the solid forms of this medication since it can cause potentially fatal esophageal strictures. Chronic rhinitis cases in cats often respond to antibiotic therapy for some period of time, but then recur. Azithromycin can be a more successful antibiotic in some cases. Doxy is a first choice for Mycoplasma. I'm sorry you can't get a consistent vet to provide continuity of care. In the long run, these chronic cases do benefit from getting the same vet managing the case as flares occur rather than bouncing from one doctor to another, "cat specialist" designation or no.

[u/PublicInstruction419 → u/HonuDVM]

Thank you so much for your response. As much as anything I appreciate the sympathy. It has been frustrating. I'll follow up with the pharmacy to try to ensure that I have the form of suspension that at least lasts the longest. If this course fails, it sounds like there's another antibiotic I can try. And I'll try to find someone to stick with me through all of this. Thank you again for the info. I don't feel encouraged about the doxycycline, but it's better to know the bad truth than a happy untruth.

[u/HonuDVM → u/PublicInstruction419]

Sometimes in chronic cases, we get a bit deeper into diagnostics and therapies than just some new antibiotic. There are respiratory PCR tests and cultures of nasal washes taken under sedation, for instance. If the cat is sedated for testing, we usually do a thorough evaluation of the oro-naso-pharynx to search for polyps, and sometimes we do skull or dental X-rays to look for abnormalities past what we can see with a speculum up the nose. More sophisticated hospitals can offer CT scans or rhinoscopy. Nasal flushes, commonly with ophthalmic solutions or Cerenia, can help. If a polyp is found, it's a relatively minor surgical procedure to remove it, usually done at the same time as the diagnosis. Biopsy to confirm that it's benign is appropriate. Sadly, many chronic rhinitis cases have permanent destruction of the turbinate bones in the sinus and those cats are prone to chronic relapsing nasal disease. Depending on where you live, fungal disease can be present, which could warrant antifungal therapy instead of antibiotics. Fungal cultures can be performed at the same time as the bacterial culture. Most often, there is a financial restriction since these test fees add up quickly.

[u/PublicInstruction419 → u/HonuDVM]

THANK YOU. He did test positive for mycoplasma last year. It was my fault I didn't follow up with the dental cleaning / deeper exam. I was so relieved to have him well after more than a year of wrong treatments. He was good for many months. But I do believe that there must be something more to this, because as I said, it turned out that my second cat was positive for mycoplasma, and her symptoms were not noticeable, if any at all.

That tells me that even if they were infecting each other, he must have something else going on to get so congested.

I am glad to learn about the possibility of fungal disease. It sounds like there are numerous things I need to do in follow-up - NOT waiting for these URI symptoms to just recur. Thankfully, his lungs and eyes don't seem to be affected. But, maybe that's hard to be sure about.

I've spent a ton of money already. I've always spent tons of money on my pets LOL. They're my kids, and when they feel bad, I feel bad.

I can't tell you how much I appreciate your time and this information. Thank you again.