Ivermectin Drug Interactions in Cancer Treatment for Dogs
"We are providing care, love, and a home for an 8½-year-old short-coat Wheaten Terrier whose elderly owner had to go to a nursing home. Ginger has skin cancer, which has manifested in a kidney-shaped tumor about 5 inches in length near the base of her rib cage on her right side. We apply a Mozotic suspension ointment to a gauze pad, then wrap it well once a day.
There are also two small lesions forming under her left eye and one on her left outer thigh near her knee. We picked her up from the vet who was caring for her, as our daughter works there as a tech after she told us the whole situation. The elderly owner's sister, who took custody of Ginger in VA and transported her here to the vet, was going to euthanize her last week, as they have a dog and aren't allowed more than one where they live.
We went to see Ginger the week before this was to occur, but after our meeting, she was energetic and lively, and my wife and I both agreed it was not her time. I'd like to try the sheep drench ivermectin protocol orally per your article's directions.
Ginger is currently on gabapentin 100mg twice a day, 100mg every 24 hours, and prednisone 10mg every other day. She weighs about 25 pounds. Can you advise if there are any contraindications with ivermectin dosing with these other medications she’s on? She is such a sweet dog, and I feel like I need to do all I can to mitigate this cancer. Thank you!"
Related: Can Cancer in Dogs Be Treated With Ivermectin?
Possible Ivermectin Contraindications
Unfortunately, not much information is available on this for several of those medications in dogs. In human medicine, we do know that some drugs are contraindicated when giving ivermectin (1). None of the medications that she is on at this time are listed as contraindicated in dogs taking ivermectin.
However, I have read some reports of certain antibiotics from the type that includes cefpodoxime being less effective. Her dose may need to be altered, but since I did not prescribe it, your regular veterinarian would need to decide whether he or she wants to alter the dose or switch her to another antibiotic.
You need to let your veterinarian know she is on ivermectin in case he decides to prescribe any other medications.
The medications we know cause problems in dogs include:
Cyclosporine: This is an immune suppressor that is sometimes used to treat autoimmune and other skin diseases, as well as several chronic inflammatory diseases.
Ketoconazole (and other azole antifungals like itraconazole): This medication is used to treat fungal infections. The ointment you are applying to her wound has one of these medications (clotrimazole), but since it is topical and such a small amount is going into her bloodstream, I do not think it is going to affect her ivermectin levels. If you are going to use ivermectin and Ginger develops an unrelated yeast infection, use a therapy like vinegar and coconut oil instead or oral ketoconazole.
Erythromycin: This antibiotic is used for several types of infections, including skin and pneumonia.
Spinosad: This flea treatment may cause ivermectin to become toxic. In a study, neurotoxic signs were found in dogs, so if she is using this medication, it can cause her to fall over and have seizures if she is on ivermectin (2). If you are using this flea control for Ginger, be sure to put her on an alternative product that your veterinarian sells.
Amlodipine besylate: This is a human medication used for high blood pressure, but it is mostly used in cats.
Aspirin: If Ginger is taking any over-the-counter medications, like an NSAID or an antihistamine, be sure to let your veterinarian know before starting the ivermectin. This has only been seen in humans, and the interaction with ivermectin is still not clear.
I certainly cannot tell you that ivermectin will help. Even if she had the tumor removed, it sounds like it is already advanced since you said you have noticed two other tumors. The estimated survival time with a melanoma, which is what this sounds like based on your description, is between one month and less than a year.
It may be something else, however, and I cannot tell you unless it is biopsied and the cells are examined by a pathologist. If it is melanoma, the only therapy that has been proven to extend lifespan is surgery.
Related: Can You Treat Skin Cancer in Dogs Naturally? (Without Surgery?)
Consider Switching to a Ketogenic Diet Too
What I would encourage you to do, in addition to trying an alternative treatment like ivermectin, is switch her to a ketogenic diet, as her tumors will not be able to continue growing without adequate glucose. I am not sure of her living situation at the moment, but if you want to provide her with an excellent quality of life in the time she has left with you, making up a ketogenic diet can do that.
The diet is mostly made up of meat and other fresh foods, not the cheap carbohydrate fillers that go into the dry diets that dogs normally eat, so most dogs love the change. If she does not want the new food, you can continue feeding her the diet she has been on.
One of the biggest problems we see with chronic cancer patients is cachexia, when they develop depression and an unwillingness to eat. The homemade diet I outlined in my article will help with that. It will take more effort on your part, but it sounds like you are already doing a lot for her.
No Reason Not to Try Ivermectin
Ivermectin may reduce the development of metastatic tumors in the lungs, so it may benefit her. As long as her liver values are normal, there are no reasons not to try it if you do not want to go with surgery.
Sources
González Canga A, Sahagún Prieto AM, Diez Liébana MJ, Fernández Martínez N, Sierra Vega M, García Vieitez JJ. The pharmacokinetics and interactions of ivermectin in humans--a mini-review. AAPS J. 2008;10(1):42-6. doi: 10.1208/s12248-007-9000-9. Epub 2008 Jan 25. PMID: 18446504; PMCID: PMC2751445. https://pmc.ncbi.nlm.nih.gov/articles/PMC2751445/
Dunn ST, Hedges L, Sampson KE, Lai Y, Mahabir S, Balogh L, Locuson CW. Pharmacokinetic interaction of the antiparasitic agents ivermectin and spinosad in dogs. Drug Metab Dispos. 2011 May;39(5):789-95. doi: 10.1124/dmd.110.034827. Epub 2011 Feb 14. PMID: 21321059. https://pubmed.ncbi.nlm.nih.gov/21321059/
