Why you need to ask your vet about pet drug interactions & side effects

Discuss potential medication side effects with your vet

In the middle of a busy veterinary practice, many veterinarians may overlook an opportunity to discuss the possibilities of drug interactions and pet medication side effects. For example, many commonly prescribed nonsteroidal anti-inflammatory medications (NSAIDs) can sometimes cause digestive upset and/or liver/kidney problems in some sensitive pets. Corticosteroids like Prednisone can cause similar problems in some pets, as well as predispose pets to diabetes with prolonged use.

While a topic of debate, these risks are increased if Prednisone and nonsteroidal anti-inflammatory drugs are used together.

While potentially lifesaving, antibiotics can also cause allergic reactions from digestive upset to skin irritation. Some pets are sensitive to topical flea and tick medications, and in my practice I always administer topical flea and tick medication on a separate day from heartworm preventative medication or vaccinations, in order to lessen the burden on a pet’s immune system.

Whenever multiple drugs are prescribed it is always important for pet owners to ask questions, because veterinarians not only prescribe pet medication but are also dispensing these medications in private practice.

Do you have a question on potential pet medication interactions or side effects? Leave a comment below. 

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  1. We recently bought a black lab and are really excited. We just are unsure on what to do about vaccines and meds? Is there a preferred place to get it done? I think that is great advice to watch for allergic reactions when administering meds.

    • Never take a double+ vaccine, meaning dog gets ONE shot covering 2, 3 or more different issues. Each shot should be separate vaccine. Never vaccinate for more than 1 or 2 things at one time. Return following 90+ days to get other vaccinations. Vaccinating can result in overdosing pet with toxicity and cause short or long term health problems as well as possible shorten their lives. I’ve heard 3 yr rabies vaccine (one shot) is better than 1 year.

  2. I personally am a minimalist when it comes to vaccinations, as most pets are overvaccinated today, which may lead to all sorts of chronic allergic and immune mediated diseases. I would wait until puppy is 14 to 16 weeks old and get one modified live viral parvo/distemper vaccination, which should give years to life time of immunity. Rabies should be given a few weeks later, but not at same time. Best done at vet. Vet can also get pet started on heartworm medications and have stool checked for parasites, etc

    • I agree Michael. Over-vaccinations cause health problems (cancer, liver damage, etc.) and they are unnecessary. I vaccinate my labrador for rabies and give oral meds for heartworm month. Nothing else.

  3. My little jrt was not eating, was sick once, had diarrhoea once and very lathargic. Took her to the vet and prescribed clavaseptin and metronidazole! Despite wanting to eat she just couldn’t. All tests normal. Referred to specialists all tests normal! Stopped medication early as found out the side effect of the meds were the same as what she was being treated for!!!!! After a week of not eating and 3 lots of iv fluids I stopped meds early and guess what…….she’s alot better. If I sussed out it was the meds why couldn’t the vet! If I had kept her on the pills and she was still not eating they were going to insert a feeding tube! The pills can cause lathargy, anorexia, nausea, etc. All what she was suffering!

    • So sorry Joanne to hear about your mishaps. Yes many of my traditional veterinary colleagues often lose site of the fact that prescription medications can cause side effects from diarrhea, loss of appetite, vomiting, etc but sadly often dont acknowledge it in their practices. Same with vaccinations, pesticide use, etc. Glad to hear your dog is feeling better

  4. michelle frankenberryApril 20, 2016 at 8:59 pm · Reply

    my brothers dog is on anti seisure meds. what kind of flea medication can he use?

  5. Can cats take albon and clindamycin at the same time

  6. Yes, but should be under care and/or guidance of your local veterinarian.

  7. Can I give my dog methocarbamol, rilexine and carprofen at the same time

  8. Hi,

    My golden retriever has dilated cardiomyopathy. One of the meds she takes is furosemide. As she also has osteoarthritis, we use Deramaxx to control her discomfort and pain. I’ve read mention of issues with raking these two drugs at the same time, and I’ve also read that there is a slim chance that Deramaxx can cause respitory problems. Should I discontinue the Deramaxx?


  9. HI Jackie. I would not discontinue the deramaxx, unless your local veterinarian treating your animal has advised that to you. I have not heard of this interaction between these two drugs in clinical veterinary practice, although anything is possible. I have not heard of this drug causing respiratory issues in dogs. Also if your dog is on long term deramaxx and/or furosemide, then periodic liver/kidney blood monitoring by your local vet is recommended. To answer Becky’s question above, I dont think there is a problem between the three drugs you ask about, but should be under the care and supervision of your local veterinarian for proper monitoring, etc

  10. My dog has had seizures so my vet prescribed phenobarbital. He has a sinus infection and head stopped up so he just prescribed Amoxcillian/Prednisolone for twice a day to get rid of it. It looks like it will last about 7-10 days. Hard to tell by looking at the bottle. Is this okay? Can he take these together?

    • I would follow your veterinarian’s prescribed directions and medications. I dont see a problem with this combination, however if any concerns come up, see your local vet

  11. Can I give my dog Nex Gard while taking Deramaxx?

    • While I dont use Deramaxx very much in practice, I am not aware of a drug interaction, as far as I know. However you could check with your local vet and/or a 1800petmeds pharmacist to be sure

  12. Can my cat take terbutaline and pimobendan at the same time?

    • I have not heard of a problem with these two drugs, although I have rarely if every used them together. I would check with a 1800petmeds pharmacist to be certain

  13. Is Temaril P ok to give my dog while he’s on a course of antibiotics? Thanks y’all! 🙂

  14. I have used temaril P with antibiotics quite frequently in practice without a problem.

  15. We took cat to the vet with what sounds like nasal respitory problem and we also noticed that right pupil is slightly more dilated. Our cat was given Rilexine 75 for sinus infection. After reading leaflet and looking at websites, nowhere can I find that this is correct thing to give for sinus infection. Is that correct antibiotic? Done 2 days so far and can’t see any side effects. Thank you

    • Rilexine is a brand name for the generic first generation antibiotic, long used in small animal veterinary medicine, known as cephalexin. While this antibiotic is safe, it is certainly not my first choice for a sinus and/or neurological infection, especially in cats

  16. I was supposed to give my 3 lb pom .5 ml of Mitotana 80 mg/ml Suspension. However, I had a new syringe and I accidentally gave her 2 ml. What should I do??

  17. Hi, my dog has been suffering with cluster seizures & just started Phenobarbital in addition to the Keppra he has been on for a year. Today, my vet gave my dog a Convenia injection for a minor believed flare up of pancreatitis. His seizures were getting better & seem to be increasing since getting the injection. Are there any known interactions between these drugs?

    • I am not fan of convenia injection for a supposed “pancreatitis” episode, although it is convenient. Drug interactions are rarely possible, as is the fact that convenia can rarely cause neurological reactions in very sensitive patients. It is also possible that your dog’s seizure disorder is just getting worse. A consultation with preferably a veterinary neurologist is recommended in your area if possible.

  18. My Lab mix has recently been diagnosed with Addison’s. Treatment with Percorten and Prednisone. I am concerned about giving and using flea and tick products, immunizations, and heart worm prevention products. Some research shows that they can cause stress and increase in symptoms of Addison’s. I gave Nexgard and Interceptor on different days and noted weakness in the hind legs several days later . This had cleared after starting Addison’s treatment. Do you have any advice or information? Thank you.

    • HI Debbie. All excellent questions. Any pet with a chronic immune mediated or hormonal disease may be at increased risk for reactions to either vaccinations and/or routine pesticides used in other patients in traditional, clinical practice. You may want to seek out the advice of a holistic veterinarian in your area. For a list of holistic or homeopathic vets, see www. AHVMA.org or http://www.drpitcairn.com

  19. My cat has an uri. He was given three daily doses of aminophylline. Now prescribed antibiotic baytril. Indications suggest drug interaction between the two. How long should I wait to give baytril dose to avoid drug interaction?

    • Time during the day does not matter when meds are given. The drugs interact if used in high doses and/or if used long term. I would check with your local vet on this, as I normally dont use Baytril for simple URI’s in cats, as there are many other approved choices out there for cats in this drug class.

  20. My dog has sub aortic stenosis and a back injury, she is on long term prednisone 2.5 mg every other day and I give her tramadol 25 mg about twice a month when she is in pain. My vet recently gave her an injectable antibiotic convenia because they thought she had mastitis (about 2 weeks ago) without telling me the potential side effects of the drug. I thought they were doing an injectable because we are suppose to treat infections aggressively due to her heart condition. She is also on trifexis because she has an allergy to skin treatments for fleas. I’ve noticed she seems swollen a lot more since receiving the antibiotic but acts normal. Do any of these medications have interactions. She is a 10 year old pug. I take her to an animal chiropractor to adjust her spine since she can’t be put under anesthesia. Her back problems have caused minor neurological problems (a little wobbly when she walks) but since having adjustments done it has stabilized.

  21. Can I give my dog her Heartguard plus and Nexgard while she is taking the antibiotic Clavamox?

    • Heatguard and nexguard should not be a problem, but I prefer to dose them separately by at least 7 to preferably 14 days as that is gentler on their bodies

  22. Two weeks ago my yorkshire terrier had some teeth removed and was prescribed tramadol and gabapentin for pain, which we stopped giving him a week ago. In the past week he vomited a few times and in one instance there was blood in it. We took him to his vet who prescribed carafate, flagyl and baytril. We’re waiting for blood test results. This seems like a lot of meds for such a small dog. Is it possible the pain meds have something to do with the blood in his vomit? Is it OK for him to be taking these other meds at the same time?

    • Tramadol and gabapentin typically dont cause bloody vomiting and/or diarrhea but every patient is an individual. OTher pain drugs like nonsteroidal anti inflammatory meds like metacam or rimadyl or more likely to cause digestive upset, however the anesthesia procedure, and meds used at that time, can lower blood flow to the gut and pancreas leading to potential problems with those organ systems post dental in some dogs. The baytril sounds a bit excessive to me based on what you are telling me briefly here, however I would wait for the lab test results and hopefully that will guide the best treatment by your local veterinarian.

  23. Can I give my dog sentinel spectrum while she’s taking Apoquel?

    • I dont think giving sentinel while taking apoquel should be a problem, but I would ask your local vet to confirm, as I dont know your dog’s individual history

  24. Hi,

    I took my cat to the vet about 3 weeks ago. I hadn’t taken her to a vet since she was a kitten, so this was the first time she’s gotten a check up in a while (she’s 7 years old.) During the checkup they found a grade 3 heart murmur, so we started her on 1/4 81mg aspirin daily. This week, I noticed she was all of a sudden limping and not putting any weight on her front paw. When I took her in they tried pinching her really hard all over her paw and determined that she had decreased sensitivity in that paw. Because of that, and the heart murmur, they think she threw a blood clot.
    They gave me a steroid (Vetalog-Triamcinolone) for her paw to help it become less inflamed, said to increase the 1/4 81mg aspirin to once daily, and start giving her Benazepril.
    Everything I’ve read online says to be very careful with giving aspirin to cats, so I’m concerned with increasing the dosage – and especially combining it with the steroid. Do you have any recommendations?

    Thank you

  25. can my pug take tramadol and temaril p and also his heartgard?

  26. My dog has been taking Metronidazole for the last four days.She’s due for her monthly Heartworm dose at this time,which contains Ivermectin only.Is it ok for her to be taking both at the same time as far as interactions are concerned?


    • I dont see a problem taking these at same time, however if your pet is being treated for a current digestive flareup with the metronidazole, it may be best to check with your local veterinarian on whether to wait on dosing with the heartworm medicine until the current problem is under control

  27. Can my lab take simplicef with rimadyl?

    • Taking rimadyl and/or simplicef during the same time period is usually not a problem or concern. If anything comes up clinically for your dog, see and/or ask your local veterinarian

  28. My girl dog has a seizure disorder and takes phenobarbital for it. She has sensitive skin and is having a flare up. She was not on the phenobarb when previously prescribed Temaril-P and Enrofloxacin. Is it ok to give her these meds with the phenobarb?

    • I would check with your local veterinarian as while this usually ok to use these meds at same time, in some rare cases enrofloxacin can occasionally predispose epileptic patients to increased predisposition to more seizures although I have rarely seen this in clinical practice

  29. Can the new Apoquel and prednisone be given together at the same time?

    • It is possible to theoretically use prednisone and Apoquel at the same time, but I would check with your local vet who prescribed them, as both can be immunosuppressive and we usually dont prescribe both together in most cases

  30. Is it safe to give prednisone 5mg, tramadal 50, and penicillin together? Once a day with prednisone. Twice a day with tramadal and penicillin. My dog is approx. 14 years old.

    • Hi Nicole. There should be no problem using these drugs together at same time if your vet prescribed them, however certainly check with your local veterinarian if you have any questions and/or concerns, as he or she knows your pet best

  31. My Schnoodle has had UTIs consistently. Culture showed Baytril would be best … Tried this a couple of months ago and it made her sick every time. So I discontinued Baytril. We have tried several others to no avail.
    I’m trying Baytril again and give to her only after she’s eaten. She “grazes” so my plan is to withhold food in the afternoon and then give Baytril after she’s eaten.
    Is it ok to give her Cerenia along with the Baytril? It may help but I don’t know about potential interactions.
    Please advise.
    Many thanks

    • I have not seen problems in pets on both baytril and cerenia at same time. I would ask your vet for referral to vet internist in your area to see if full workup done. An ultrasound also may be needed to look for hidden stones, etc

  32. Leeann BlakemoreAugust 1, 2016 at 1:05 pm · Reply

    My 17 lb Boston Terrier was diagnosed with left caudal pneumonia 3 days ago. Taking clavamox and Baytril. Home today day 4 and continues on those meds orally. His Heartgard Plus is due today. Can it be given or should we wait ?

    • Probably best to wait until pneumonia resolved and pet completely back to normal. I am sure your local veterinarians can advise on optimal time to restart the heartguard

  33. Hello, I have a 12 year old cocker spaniel that has a gallbladder mucocele, unfortunately not a candidate for surgery, He is currently on denosyl 25 mg chewable and Ursodiol 150 mg daily, He has a very bad skin infection and the vet added Zeniquin 25 mg, 1and 1/2 pill a day. I just wanted to make sure there are not drug interactions by adding the Zeniquin to his other 2 medications. Thank you!

    • I dont see a problem with the Zeniquin and other meds, however if any symptoms change, you should be in touch with your local veterinarian who can provide more specific dosing advice

  34. Can Apoquel be given to a diabetic 19.8 lb Havanese currently on Denamarin?

    • I dont believe this is a contraindication for apoquel, however I would check with your local vet. Any pet who have pancreatic and/or liver chronic problems should have CBC.chemistry blood profiles done before going on Apoquel and then every 6 months if placed on it long term

  35. I have a 30 pound Beagle who is currently on an antibiotic for an anal gland problem. I am starting her on NexGard for flea and tick protection. I was wondering if there is any kind of a drug interaction in these two meds.

    • As far as I know, nexguard does not have any major contra indications with any antibiotics, however I would prefer that you wait until anal gland issue and infection is resolved before starting any oral pesticide medicine like Nexguard. Check with your local vet who knows your pet best

  36. My 11 year old 4 pound chihuahua is on phenobarbital 1/4 tab twice a day for seizures since May. he suddenly got weak and didn’t want to eat or move around last Wednesday I took him to the vet and he said his heart has fluid around it so he prescribed 0.1 ml of benazipril 0.15 ml of furosemide and 0.5ml of Pimobendan is it safe to give him all 3 heart meds at the same time and sometimes with the phenobarbital? He was also given amoxicillin for a bladder infection. It just seams like a lot of meds for a little guy.

    • Hi Ashley. Does sound like ALOT of meds for a little 4 pound guy. All 3 of those meds are perfectly appropriate for congestive heart failure secondary to mitral valve insufficiency in toy breeds, but you may want to have your vet send x rays off to radiologist to confirm and/or ask for referral to vet cardiologist if you want confirmation on diagnosis, which I cant do from this end. Usually dogs with congestive heart failure, however have increasing difficulty coughing, difficulty breathing, and history and/or recent loud heart murmur. If your little guy had none of these(as you only described weakness and loss of appetite), then I would question this diagnosis and get second opinion. Amoxicillin is fine if he has urinary infection as well. You may want to consult with holistic veterinarian as well for additional support for this little guy. To learn more about holistic medicine, see http://www.doctordym.com Many holistic vets offer phone consultations

  37. My rescue dog, of indeterminate age (over 7 yrs) and breeding, but probably some husky and maybe some collie, has many, many health problems, and is on many, many medications. The Internal Medicine specialist vet suspects an underlying autoimmune problem, but right now my dog is being treated for long-standing IBD, arthritis, hypothyroidism, Diabetes mellitus, pancreatitiis, (the latter two probably triggered by a very bad reaction to steroids) and now a urinary tract infection. She takes the following meds: Gabapentin (for arthritis pain), Thyroxine, Humulin N, Sucralfate, Metronidazole (for diarrhea), OTC Omeprazole (antacid), OTC VSL #3 (probiotic), and weekly injections of Cyanocobalamin. We have finally got her diarrhea mostly under control, and the latest bloodwork showed her pancreatic functioning is back to normal. Now the vet is adding Clavamox for a UTI. I read that one of the possible side effects of Clavamox is diarrhea, which worries me. I also read that Clavamox “can react with some antacids”, but didn’t see what that reaction might look like. I’m so worried about all these drugs with her fragile condition. Do you see any drug interactions I should be concerned about? How would I recognize them if they are happening? Should I increase the probiotic while she is on the antibiotics?

    • HI Ann. Sounds like a traditional medical mess. Also sounds like you have had excellent workup at your local traditional vet and specialist. Clavamox, like any antibiotic can cause diarrhea in some sensitive patients(its human equivalent is augmentin, which also can cause digestive upset in people). I personally prefer quinolone antibiotics in case like this such as Baytril or zeniquin, but you would need to ask your local allopathic vet about these options. I would certainly not have a problem increasing your dose of probiotics or digestive tract enzyme supplementation on case like this, but you also may want to consider a consultation with a homeopathic or holistic veterinarian in your area. See website http://www.drpitcairn.com for a list of homeopathic vets with appropriate training. Sounds like this is a traditional veterinary medical rollercoaster with no end in site, which is why I think you may want to consider and/or learn more about a holistic approach being incorporated in the treatment plan as well

  38. I am going to give my dog who is 10, has a tumor his sinus Metacam and Mirtazapine.

    What are the drug interactions that I can expect when I do. I know one makes them lose appetite and the other is an appetite booster. What are the side effects of the two being administered to him?

    • Metacam, like any nonsteroidal anti inflammatory medication can occasionally cause digestive upset and/or in rare cases liver and/or kidney issues or even more rare ulceration of digestive tract. Mirtazipine is actually a human psychotropic drug that veterinarians sometimes use in dogs and/or cats to stimulate appetite, as that is a side effect of its use in human psych patients. Side effects are rare with mirtazipine and can include neurological and/or behavioral changes, but vets have found this rare. No specific interactions between these drugs that I am aware of if your vet prescribed them. If you are concerned, I would see your vet for recheck and assessment

  39. My corgi was just diagnosed with Cushings. The vet started her on Elapril, 1/8 coated baby aspirin and melactin supplement while waiting on all the blood work results. She said we could just keep her on those to protect her kidneys (her only symptom is drinking A LOT and peeling A LOT) or use the Cushings meds. I ordered Cushex yesterday. My question is, do I keep her on the Elapril and other stuff while using the Cushex or not?

  40. I would follow your vet’s instructions regarding using the enalopril, which is a blood pressure medication that is also used to lower urine protein loss, which is common in dogs with Cushings Disease. I would ask your local vet about any interaction or concern between Cushex and the enalopril and go from there.

  41. Is it safe to give my cat gabapentin and prednisolone together?

    • HI Terri. I have not seen problems when I occasionally use this drug combination together, however your cat should be under the care and monitoring of the local veterinarian who prescribed them.

  42. Can my dog take Claritin and prednisone at the same time? He’s suffering from terrible seasonal allergies.

    • I have seen no problems with pets taking drugs like claritin and pred at same time but check with your local vet who prescribed the pred for confirmation on this individual case. You could also ask about new drug called apoquel as well

  43. Trifexis and Cephalexine. Yes or no to a drug interaction? Dog was prescribed Cephalexine for a bacterial skin infection. She also takes trifexis for heartworms. Any problems with these two drugs interacting?

  44. My two year old female cat CoCo has been fur mowing on her abdomen and tail. We (with the Vet) have ruled out parasites and think she may have hyperesthesia. The Vet prescribed amytriptiline (1/2 tablet 1x per day). After a month, there wasn’t much success, she’s slowed down, but still mowing, so we upped her to a full tablet 1x per day. Still no luck. So now I’m weaning her off the amytriptiline and we’re going to start her on 35mg of Gabapentin 1x per day. Can she start the Gabapentin before she’s fully weaned off the amitryptiline? If the Gabapentin alone doesn’t work, can I try Zyrtec with the Gabapentin? We have a second cat that has had success with his allergies (food ruled out, now guessing it’s environmental which the Zyrtec has helped). I’m wondering if maybe CoCo has environmental allergies as well?

    • HI Vickie. Excellent questions. You need to check with your local veterinarian who knows your cat best, whether he or she is ok with starting the Gabapentin while weaning off amitryptylline. I would think the only adverse reaction would be excessive sedation. As far as I know, Zyrtec would be fine to try along with gabapentin(again main side effect excessive sedation) and might help in case environmental airborne/contact allergies. You can also explore food allergies and food trials with your veterinarian. You could also consider a more holistic approach, should these stronger drugs not work for this poorly understood condition. I would get the book The Natural Cat By Anitra Frazier, as well as see some of the info on my website http://www.doctordym.com Homeopathic approaches are not quick fixes, but I have seen them help cases like this with time, patience and commitment

  45. My 5 year old female pug suffers from spondylosis and had a recent injury a week ago and is also suffering from a UTI. She is currently on the following medications: Tramadol every 12 hours, Prednisone every 24 hours, Methocarbamol every 12 hours, Clavamox every 12 hours and Methigel (for struvite crystals in urine) every 24 hours. She is due to take her Sentinel tab for heart worm and fleas, is it okay for me to administer today even though she is on all those medications? I’m not sure if there are any drug interactions.

  46. Just ordered phycox from you guys and I here wonders about the drug for arthritis. On occasion my dogs take tramidol and or previcox. Is there any interaction with these meds

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