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The Hazards of Mixing Up Flea and Tick Medication

By Krystle Vermes


If you have a dog, cat, or several pets at home that require flea and tick medication, you likely have various treatments on hand to maintain their health. However, there are serious dangers that come with potentially mixing up these products, regardless of whether they are prescription or over-the-counter.


“Dog products should never be applied to a cat and owners need to make sure they use the correct dosage for the weight of their pet,” says D.D. Clark, DVM, Companion Animal Technical Services Manager at Merck Animal Health. “Under dosing can lead to lack of efficacy.”


But aside from reducing the effectiveness of flea and tick treatments, there are other health concerns that can stem from the misuse of medication.


Flea and Tick Medications: Mixing Dangers for Cats


Several experts agree that there are dangers associated for both cats and dogs in the event that treatments are mixed. However, most of the issues are prone to heavily impacting cats.


“Cats are more sensitive to most of the active ingredients in flea control products,” says Dr. Jeff Werber, a practicing veterinarian and veterinary medical journalist. “Many flea and tick control products contain pyrethrins, which are derived from the chrysanthemum flower. Natural pyrethrins are generally not toxic to cats if used in the proper amounts. Synthetic pyrethrins on the other hand can be deadly, especially permethrine and resermethrine.”


Werber explains that cats are also sensitive to chlorinated hydrocarbon and petroleum distillates—ingredients used in older insecticides. In large quantities, these can also be toxic to dogs, but cats are more sensitive, he says.


In extreme conditions, Dr. Duffy Jones of the Peachtree Hills Animal Hospital in Georgia says that a mix-up can be potentially fatal.


“The most common danger is overdose,” says Jones. “Many times the packages can look the same and you might not notice that one if for large dogs and one is for cats. Sometimes these overdoses or using a product with pyretherins or organophosphates on a cat can be lethal.”


It’s also worth noting that cats generally have more sensitive metabolisms, according to Dr. John Clark of the Community Veterinary Clinic in Vero Beach, Fla.


“Owners should be aware of this and always read the label,” says Clark.


Flea and Tick Medications: Mixing Dangers for Dogs


While there are no toxicity risks associated with giving dogs flea medication meant for cats, it can pose a danger to canines due to a lack of efficacy, says Dr. Katy Nelson, an associate veterinarian at the Belle Haven Animal Medical Centre in Alexandria, Va. Dogs given cat flea and tick medication will not be protected against Lyme disease and other tick-borne illnesses.


Nelson also explains that pet parents should not purchase flea and tick medications for large dogs and split the dosage between two small dogs. “The main risk here is skin irritation,” she says. “You’re not going to save any money by splitting a vial of something if your pet has a reaction to it.”


Flea and Tick Prevention and Proper Treatment


The risks involved with having both cat and dog flea and tick treatments around the house does not mean pet owners should stop using these products. Flea and tick medications still provide the best prevention against dangerous parasites. But there are some tips to follow to keep track.


“Know your products and stick to them; don’t keep changing products each month,” says Clark. “Getting advice from a veterinary office can help you choose a reasonably priced flea medication that works well in your region. The technical staff will be more than willing to give you advice over the phone or in person about effective products for both cats and dogs.”


Clark adds that it might be worth scheduling routine pet medication treatments on different days for different animals to avoid a mix-up.


“If [a product] contains a pyretherin or organophosphate, you should probably avoid using them if you have a cat,” says Dr. Jones. “It does not take much for them to become toxic.”


It may also help pet owners to know the signs and symptoms of poisoning as a result of a medication mix-up. Toxic ingestion might present itself as profuse salivation, muscle twitching, weakness, and vomiting, according to Werber. Pet owners should bathe their animal immediately with Dawn dishwashing liquid and seek professional medical attention in the event that any treatment mix-up has occurred.


Image:  via Shutterstock

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