Over-the-Counter vs Prescription Flea & Tick Treatment: Which Is Best?

Author: Dr. Stephanie Austin

Published: March 15, 2021

Updated: May 28, 2024

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german shepherd and cat sitting next to each other on couchWinning the battle against fleas, ticks, worms, and other parasites takes commitment and consistency — as well as some good preventative medication!

Some of these you are able to purchase over the counter at pet supply stores, supermarkets, and big-box stores. However, others require a prescription from your veterinarian or a trip to your veterinarian’s office.

So, you may be wondering, what’s the difference? Are these over-the-counter preventatives as effective and safe for your pet as the alternative prescription versions that have veterinarian backing and support? Why is veterinarian approval important when you can just grab some flea preventatives in your local supermarket aisle? Should you switch?

Read on to make sure you’re getting the “right stuff” for your cat or dog to keep them safe from fleas, ticks, and other parasites.

Key Takeaways (TL/DR)

1. Over-the-counter medications are regulated differently than prescription medications: OTC preventatives are likely to be regulated by the Environmental Protection Agency (EPA) only, as they are considered pesticides vs. drugs. They are generally less potent than prescription medications and may only offer limited protection against fleas, ticks, and heartworms. OTC medications may also have a higher risk of adverse effects or drug interactions. Read more about the difference between OTC and prescription preventatives

2. Preventative medications require a prescription from a veterinarian: This is because they require closer regulation and oversight to ensure they are being used safely and correctly, all of which are regulated by the Food and Drug Administration (FDA).Find out what determines a preventative is OTC or prescription-only

3. A veterinary appointment may be necessary: Some prescription medications may require diagnostic testing, such as blood work, prior to being able to obtain an approved prescription to ensure the pet is healthy enough to take the medication. It is always recommended to consult with a veterinarian to determine the most appropriate medication for your pet's specific needs. Learn if OTC preventatives are as effective as prescription flea/tick treatments

4. Heartworm medication always requires a prescription: Before giving heartworm medication, you ALWAYS need to ensure that your pet isn’t already infected with heartworm, as this could be a fatal mistake if you give them medication, let's say left over from another pet. Read more about why heartworm requires a prescription and a vet appointment

What’s the Difference Between Over-the-counter and Prescription Preventatives?

Over-the-counter (OTC) Medications

Dog wearing flea collarOTC = "Over-the-Counter"

Over-the-counter preventatives are available without a prescription.

The reason some flea/tick topical preventatives are in this category is that they aren’t absorbed into your pet’s body the same way a prescription medication is; hence, no prescription is required.

These preventatives are likely to be regulated by the Environmental Protection Agency (EPA) only, as they are considered pesticides vs. actual drugs. Examples of OTC preventatives include flea and tick sprays, shampoos, dips, collars, and some “spot-on” treatments.

Commonly used over-the-counter preventatives include Frontline and Seresto.

Prescription Required (Rx) Medications

Rx = Prescription

Prescription medications require an approved prescription from a licensed medical professional before they can be dispensed, as they require closer regulation and oversight to ensure they are being used safely and correctly. This could be a tablet, capsule, chew, topical 'spot-on' treatment, injection, powder, or other forms of medication, all of which are regulated by the Food and Drug Administration (FDA). Additionally, some of these medications may require diagnostic testing, such as blood work, prior to being able to obtain an approved prescription to ensure the pet is healthy enough to take the medication.

Very few ‘spot on’ treatments fall in this category unless they also treat internal parasites, such as worms. Commonly used prescription preventatives include Bravecto, Nexgard, Sentinel, and Simparica.

What Determines Over-the-counter vs. Prescription Only?

Many factors go into deciding whether a flea and tick preventative is sold over the counter or by prescription only. Manufacturers look at these determining factors:

  • Ingredients: Where you can buy the medication depends a lot on its active ingredient(s) and the risks if applied incorrectly or given at the wrong dosage. The ingredients in prescription medications are well-controlled and regulated, compared to those in an OTC medication that may not be – meaning that over or under-dosing is much more possible.

  • How it’s administered: Is the medication a pill or tablet that’s given orally? A liquid that’s applied to your pet’s skin? Or a liquid that may need to be injected under the skin? How easy is it to use?

  • The governmental agency that regulates it: If the Environmental Protection Agency (EPA) regulates the product, you won’t need a prescription from your veterinarian as this product is considered a pesticide. If the Food and Drug Administration (FDA) is the regulator, you will likely need a prescription as this product is considered an animal drug.

cat taking flea pillWhy Heartworm Medications Require a Prescription

Protecting your pet against heartworm is more important than ever! With climate change on the rise, warmer winters, and an increasing number of pesky bugs around, that means increasing numbers of spreading diseases such as heartworm.

However, it is not recommended to start your pet on heartworm preventative without a visit to your veterinarian first.

Even if you have leftovers from other pets. You ALWAYS need to ensure that they aren’t already infected with heartworm, as this could be a fatal mistake.

Giving your dog or cat a heartworm preventative if they’re already infected won’t solve the problem — in some cases, doing so can actually make things worse and can be fatal for your pet. For this reason, the FDA requires a prescription for heartworm preventatives. So, the first step is a quick but important heartworm test, and then your vet can prescribe the right medication for your pet.

Unfortunately, there is no effective cure for heartworm in cats, which is why prevention is so important! While heartworm can be treated in dogs, treatment can be perilous and is quite expensive. Learn more in "Heartworms Suck! What You Should Know About Mosquitoes, Heartworm Disease, and Your Cat."

If your cat or dog has not been on heartworm preventative consistently, your veterinarian will likely recommend a heartworm test six months after starting the preventative for the first time (or restarting after a long break). This is because it takes approximately six to seven months from the bite of an infected mosquito for that infection to show up positive on a heartworm test. Thus, it's important to stay consistent with giving your pet their preventatives — mark it in your calendar and/or set a reminder on your smartphone.

Check out "Mosquitos: Why Cats and Dogs Need Heartworm Protection" to learn more about the dangers of heartworm disease.

Questions? If you'd like to speak with a veterinarian about flea and tick preventatives, Click here

Is Over-the-counter as Effective as Prescription Flea and Tick Treatments?

Dachshund dog getting topical flea medicationsAlthough OTC flea and tick treatments may do an okay job, they’re missing some important benefits of their prescription counterparts available only from veterinarians. This is where OTC preventatives can fall short (and may even be less safe):

  • Many over-the-counter preventatives only kill the adult parasites, giving their babies a chance to grow up and wreak havoc — leading to a vicious cycle. Not only that, OTC preventatives typically don’t have the staying power to keep killing the adult parasites, so at some point, they may stop working.

  • Most OTCs are designed to prevent only one or two types of parasites at a time (such as fleas and ticks) instead of a large number of them: fleas, ticks, ear mites, intestinal worms, and even heartworms. This may result in you having to combine multiple different OTC treatments to treat the different bugs, which can often have unwanted or unknown side effects. Prescription preventatives are often designed to work in one easy and effective treatment.

  • They’re more likely to contain ingredients that have been around for years (sometimes decades) — which some crafty parasites have since developed resistance against. This means that many OTC medications may not prevent your cat or dog from a flea or tick infestation. However, in an effort to combat this resistance, many brands are adding ingredients to their formulas, such as Frontline Gold and Frontline Tritak. Although these are still considered pesticides despite these additions.

  • giving cat flea medicationSome ingredients designed to kill ticks can be downright dangerous if there’s a mix-up. For example, if a smaller dog accidentally gets a “big dog” dose or a cat accidentally gets a dose of the dog’s flea meds, the results can be disastrous if not fatal.

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Benefits of Prescription Preventatives

Some prescription preventatives require fewer doses — for instance, one chewable pill every three months compared to a topical “spot on” treatment every month. Other prescription preventatives safely combine multiple parasite preventatives into one medication, making it easier for pet owners to ensure their pet is protected against fleas, ticks, heartworm, and other parasites with just one medication each month.

If you’re considering switching between over-the-counter and prescription preventatives for your pet, your best bet is to speak with your veterinarian about what will be most effective for the area you live in and your pet’s needs.

preventative pill for dog

Have a Talk With Your Veterinarian

The world of parasite preventatives is a big and confusing one. There is a lot to consider, such as your pet’s lifestyle, age, weight, general health, any sensitivities or allergies, as well as any other medications they may take, and if there are other pets or children in your home.

The good news is that your veterinarian can help you navigate the options, answer all your burning questions, and recommend the prevention plan that’s best for you and your dog or cat.

It’s important to let your veterinarian know about any over-the-counter flea and tick medications you’re giving your pet. By having a complete picture of your pet’s “medicine cabinet,” your vet can help you ensure that your pet is getting the safest, most appropriate prevention and care possible.

Let us know what flea and tick preventatives have worked best for your dog or cat in the comments below!

About the author

Profile picture for Dr. Stephanie Austin

Dr. Stephanie Austin

Dr. Stephanie received her Bachelor of Science (Maj. Vet tech) from the University of Queensland, Australia, in 2006. After graduation, she moved to the other side of her beautiful, sunny country, to the most isolated city in the world (Perth, Australia), to begin her veterinary degree at Murdoch University. 5 years later, she received a dual degree in Veterinary Biology and Veterinary Medicine and Surgery.

After all this schooling, Dr. Stephanie packed her things, her beloved Labrador & fluffy cat, and made the big move to the USA. She lives and practices at a clinic in the “big apple.”