Last updated Sep 8, 2022
Doxycycline is a broad-spectrum antibiotic commonly used to treat certain bacterial infections in cats. In this article, you’ll learn more about doxycycline, what types of infections it may be indicated for, side effects, administration tips, frequently asked questions, and more.
Doxycycline for Cats Overview
About Doxycycline for Cats
Doxycycline is a tetracycline antibiotic. Tetracyclines are generally time-dependent bacteriostatic antibiotics. This means that the length of time they are employed against bacteria susceptible to them is most important.
Although termed “bacteriostatic”, implying they only inhibit the growth of bacteria, antibiotics like doxycycline do actively kill bacteria. They simply require a higher concentration than an antibiotic labeled as “bactericidal”. Thus, for bacteria that are equally susceptible to them, doxycycline is not necessarily a “weaker” or “less effective” antibiotic than a bactericidal agent like amoxicillin.
Doxycycline is used to treat a variety of infections in cats, predominantly infections of the upper respiratory tract and infections caused by certain bacteria commonly transmitted by fleas and ticks.
What Does Doxycycline Do for Cats?
As with most antibiotics, doxycycline has good levels of efficacy against certain bacteria, while others may be resistant or just not susceptible to it.
For example, an upper respiratory infection in a cat caused by bacteria including Bordetella, Chlamidophila (Chlamydia), or Mycoplasma will typically be susceptible, while a urinary tract infection caused by Proteus is unlikely to be.
Doxycycline also is not effective against viral causes of upper respiratory infections in cats, like feline herpesvirus and calicivirus, which are actually by far the most common underlying causes in kitties.
Doxycycline is commonly used to treat infections caused by bacteria transmitted to cats from fleas and ticks. These can include organisms like Anaplasma, Ehrlichia, Bartonella, and Mycoplasma hemofelis (not to be confused with our Mycoplasma involved with upper respiratory infections).
Doxycycline is also effective against a bacteria called Wolbachia. Killing Wolbachia bacteria in dogs has been demonstrated to weaken heartworms, the cause of mosquito-borne heartworm disease. This effect has not been definitively proven in cats and is still being studied, though some veterinarians may employ doxycycline in treating cats with heartworm disease for this reason.
Side Effects of Doxycycline for Cats
The main side effect of doxycycline in cats is gastrointestinal upset, so giving them Doxycycline with food should help to reduce this risk.
The main side effect of doxycycline in cats, as with many antibiotics, is gastrointestinal upset, including vomiting, regurgitation, diarrhea, and a decrease in appetite.
Doxycycline should always be given with food, as this can help to reduce the chance of digestive upset.
In cats, administration of plain doxycycline tablets on their own carries a very high risk for esophagitis, ulcerations, and a narrowing of the esophagus called a stricture. In fact, the risk for cats is considered so high that many veterinarians will avoid use of the tablets in cats and opt for having doxycycline compounded into a liquid form.
When given to pregnant dogs and cats in earlier stages of pregnancy, tetracyclines in general can slow down fetal skeletal growth and discolor their teeth. Doxycycline however is the least likely of the tetracyclines to have these effects.
Unlike other tetracycline antibiotics, doxycycline can be used in pets with kidney disease. However, it should be used cautiously in cats with liver disease or elevated liver values on lab work.
Doxycycline for Cats Dosage
There is no labeled dosage for Doxycycline, but there are commonly accepted dosages for certain infections. Always consult a vet before giving a drug to your cat.
Because the use of doxycycline is off-label when treating infections in pets, there is no labeled dosage. There are commonly accepted dosages for certain infections, but some veterinarians may differ on prescribing once a day, twice a day, or for how long depending on the infection and circumstance. Always make sure to closely follow your veterinarian’s instructions.
An important note about dosing cats is that there is a high risk for kitties developing irritation and ulceration of the esophagus (termed esophagitis) and narrowing/tightening of the esophagus which is called an esophageal stricture.
For this reason, many veterinarians will prefer to have doxycycline compounded into a flavored liquid preparation for their feline patients.
If tablets must be used, direct administration should be followed by at least 6ml (roughly a teaspoon) of water to ensure that the tablet makes it all the way down to the stomach. Although doxycycline should be given with food to offset digestive upset, hiding the tablet in food and hoping it makes its way down may be less effective than ensuring its passage with a small amount of water.
As you can imagine, administering a pill to a cat and then trying to syringe water on top of that can be a real headache for you and your kitty. This is another reason a liquid form ordered from a compounding pharmacy can be easier and more successful to use.
Conclusion
Doxycycline is an effective antibiotic for certain types of infections, and certainly deserves its place as an important one to use in cats. A big takeaway is the need to reduce the risk of esophageal damage in cats caused by a dry pill getting lodged as it can be very irritating and lead to strictures. Using a compounded liquid form of the medication is generally recommended.
Another big takeaway is to remember that while it is used often for bacterial upper respiratory infections in cats, most URIs in cats are caused by viruses, not bacteria, and doxycycline cannot be used to treat these viral infections. That’s why it’s always very important for your veterinarian to decide if using antibiotics is appropriate.
Drug Dosing Disclaimer: We are only able to provide doses for medications that are FDA approved for use in cats and only as the label guidelines dictate. For medications that are used off-label we can only provide guidelines and safety information for use. Safe and appropriate dosing for off-label medications can only be determined by a primary care veterinarian.
We encourage you to work with your veterinarian to determine if a particular medication is appropriate for your cat. Changing or adjusting a dose for your cat on your own without consulting with a veterinarian can carry risk. We do not encourage use of medications prescribed for human use in pets without first consulting with a primary care veterinarian.
Frequently Asked Questions
How long does it take doxycycline to work in cats?
With most antibiotics treating susceptible organisms, improvements should be seen within 2-3 days, although the full resolution of signs often takes longer. This is why it is very important to finish out all of an antibiotic prescribed by your veterinarian. Do not stop using doxycycline or any other antibiotic based on your cat looking or feeling better.
What is the best antibiotic for feline upper respiratory infection?
The true answer is whatever antibiotic the bacteria involved in the infection are most susceptible to! This is sometimes easier said than done.
But it is important to remember that a large majority of upper respiratory infections in cats are caused by viruses like herpesvirus and calicivirus, not by bacteria. So in many cases, an antibiotic may not be indicated at all.
If your veterinarian does suspect a bacterial infection is involved, he or she may choose an antibiotic based on the likelihood of certain organisms being present. Bordetella and Chlamydophila (Chlamydia) for example, are common bacterial causes of URI's, and both are very susceptible to a number of antibiotics, including doxycycline. Sometimes, nasal swabs may be collected to run additional testing to try to determine a causative organism. But because these panels can be expensive and difficult to interpret, they are not employed often.
Is doxycycline a powerful antibiotic?
Although we sometimes throw around terms like “big gun” when it comes to antibiotics, we should get away from this mentality. Even newer generation antibiotics can have bacteria resistant to them.
Doxycycline is an effective antibiotic against most of the bacteria typically susceptible to it. Veterinarians typically determine antibiotic use based on bacterial culture whenever possible or at least based on the likelihood of infectious organisms present, and the body system affected.
For example, while doxycycline can have a high level of success for a bacterial upper respiratory infection in a cat, it will likely do very poorly if used for a urinary tract infection because the types of bacteria found in each case are different.
And although doxycycline is a bacteriostatic antibiotic, it is not necessarily “weaker” than a bactericidal antibiotic like amoxicillin. Bacteriostatic antibiotics do kill bacteria, they simply require a higher concentration to do so.
A 2018 study in Clinical Infectious Diseases comparing bacteriostatic and bactericidal antibiotics in people highlights this distinction. Researchers found that not only were bacteriostatic and bactericidal antibiotics about equivalent in efficacy most of the time, but that in cases where there was a difference, bacteriostatic antibiotics often appeared superior and more cost effective.
Kitten weighing 1,5lbs was prescribed the liquid doxycycline, 100mg, and dosage is .1 ml twice a day for an upper respiratory infection. Does this seem to high?
Hi Shannon,
I would need to clarify a couple details to best answer your question. First, by 1,5lb does this mean 1.5lb, as in less than 2lb? Not 15lb? Second, the liquid has to be expressed as a concentration somewhere on your bottle’s label, in mg/ml. You stated 100mg, but it can’t just be in mg. If you can clarify those for me, I can get back to you.
Right, under 2 pounds. On the bottle it says 100mg/ml.
Hi Shannon,
The 0.1ml at a 100mg/ml concentration is a little higher than a 10mg/kg dose for a 1.5lb kitten. However, there are some things to consider. One is that the exact 10mg/kg dose is 0.06ml. You don’t want to go below that because that would be underdosing and may be less effective. Doing exactly that volume might be a challenge for some folks to measure out, where 0.1ml is more straighforward. Your kitten is also growing, and using the 0.1ml ensures that as they grow over the two weeks or more they’re getting the doxycycline, that they’re getting an effective dose as long as they don’t exceed 2lb. If your kitten hasn’t shown any digestive upset side effects, it’s probably best to continue the dose as prescribed.
When using Doxycycline in capsule form which is easily mixed with food would 50ML be a good dose daily for a feral cat with upper respiratory issues and perhaps eye infections ?
Hi Frank,
There are some contradictions here in your question. You mention Doxycycline in capsule form but then a dose volume in ml. I don’t want to make any assumptions there. If you meant milligrams, then 50mg would be an average dose for the average cat weighing 10-12lb but doxy is not appropriate for all cases, so I couldn’t tell you for sure if it would be effective. If you were planning to just hide the capsule in the food, this can carry a risk of esophageal strictures in cats. If you were planning to puncture the capsule and mix the contents with food, I really couldn’t say whether the ingestion/absorption of it that way would be appropriate or effective, as that’s not how it’s intended to be used. It would also depend greatly on if the cat eats the meal in one sitting and how many other cats might have access to it. My preference with doxycycline for cats is to always get it compounded into a liquid form and give that directly. I realize you can’t do that with a feral cat, but important to understand that would be the most effective route.
What to do if you miss a dose of doxycycline in cats?
Hi Dorothy,
This depends on whether it is being given every 12 hours or every 24 hours. My general rule is for an antibiotic medication being given every 12 hours, to wait until the next dose is due if more than 6 hours have passed since the missed dose. So if the dose was due at 6am and it’s approaching noon, you can still give the missed dose ASAP. You can still give the next dose that evening, though you might wait until a little later that night, like maybe 9 or 10 oclock to apporoach that 12 hour mark as close as possible. If it’s closer to 3 or 4 pm, it might be best to just wait until 6pm when the next dose is due.
For an antibiotic medication being given every 24 hours you can consider giving a missed dose up to 12 hours after it was due. If more than 12 hours has passed, it may be better at that point to wait until the next dose is due the next day.
For example, if it was due in the morning and it’s now approach evening time, you can choose to give it in the evening. But if you do that, this would shift the time of day you’re giving it now to the evening time from that point forward. But if you happen to remember late that night that you forgot the dose that morning, it may be best to wait until the morning to give the next one.
Those are general guidelines of course. If you have more specific questions based on how the doxycycline was prescribed, it’s always best to ask your veterinarian.
I am giving my cat doxycycline in liquid form. My question is do I have to follow up with water when it’s in liquid form or is that just necessary when it;s in capsule form. He does eat his food after approximately 5 minutes after dosage. The water seems to be worse than the medication. Thank you.
Hi Nadine,
This is a great question. Generally, if you get doxycycline compounded as a liquid, this eliminates the need to follow up with water. The esophageal strictures that cats are prone to with doxycycline relate soley to dosing of the oral tablets. It’s because of the risk the tablets pose and the inconvenience of having to squirt water afterwards to flush the tablet down that many of us elect to prescribe it as a compounded liquid instead, removing that risk (and the extra water).
Where is research using doxycycline in cats with lymphomic cancer?
Hi Marianne,
Doxycycline is not used primarily for treatment of lymphoma in cats (or other species to my knowledge). In doing a quick peer-reviewed article search, I did not see any studies evaluating doxycycline use for lymphoma either.
Doxycycline does have anti-inflammatory and immunomodulatory properties, so it’s possible there may be some cases where a doctor may find it advantageous to use, even if it’s not functioning as a primary treatment.
There are also cases where doxycycline may be used to control secondary bacterial infections in cases where lymphoma is also present. Examples could include cases of cutaneous (skin) lymphoma as well as lymphoma in the nasal passages or sinuses, where secondary bacterial overgrowth and related complications can be common.