Last Updated: 28/05/2025
Wondering if you can split parasite prevention in half? Read more about the reasoning and when you can and cannot split parasite prevention for your pet.
Author: Dr Carla Paszkowski BVSc (Hons)
Reading Time: 21 minutes - medium read
We often hear from pet owners asking if they can split their pet's parasite prevention. There are various reasons why someone might consider this, and while it's sometimes acceptable, it's not always the case. Let's explore the details of splitting parasite prevention medications.
Many people with small dogs, or multiple animals in the house, may want to buy a large dog chew and split it between their pint-sized pups. Maybe your dogs are different sizes, and it seems more affordable to buy one packet, rather than multiple? Or maybe you have one pooch, and want your pack to last twice as long?
It's easy to assume that if you have a small dog who weighs 5kg, you should be able to buy a tablet for a 10kg dog and halve it; especially if the medication dose seems to line up as an even double. However, manufacturers usually advise against this, except in certain circumstances. See below for more about this.
Perhaps you don't intend to divide the dose, but you just want to split a chew into smaller pieces so it is easier to give. Or maybe you want to crush a tablet into something palatable, such as wet food, so your pet will accept it.
In general, this is usually fine so long as you can guarantee your pet will receive the entire dose. However, there are certain circumstances where this is not advised.
An easy way to check is by looking at whether the medication is meant to be chewed or not - usually indicated by the word 'chewable' on the product packaging. A chewable medication will be crushed up by the time it reaches the stomach, whereas some pills or capsules may need to be given whole, with an intact outer membrane, to ensure that the medication is absorbed into the body appropriately.
Note - this only applies to parasite prevention. If you wish to crush another type of medication into food, such as pain relief or antibiotics, we recommend you check with your vet beforehand.
You can split pills if:
The tablet is 'scored' with a clear graduated line down the middle
This is a sign that the manufacturer created the medication to be 'okay to split'. A split line also makes it easier to break evenly, reducing the risk of over or underdosing.
The medication comes with instructions for splitting
This is commonly seen with some brands of wormers such as Drontal or Milbemax tablets.
You are able to use the remaining portions within a reasonable time frame
Many tablets will disintegrate when they are removed from their packet and broken. In some cases, this can reduce the efficacy of the medication.
You intend to give the whole dose, but just want to split the medication into smaller pieces to make it easier to give
For example, if your dog or cat won't eat a chew, or a tablet is too large, it usually fine to split it into smaller pieces or crush it into food, so long as you can guarantee that your pet receives every part. However, as mentioned before, this only applies to parasite prevention. If you wish to crush another type of medication into food, we recommend checking with your vet first.
You have been instructed by your vet to do so
This may be the case with some topical applications, such as Revolution, which can be dosed in partial amounts to small pocket pets such as rabbits or guinea pigs.
You should never halve medication if:
The medication is not 'scored' with a clear graduated line down the middle
Most chewy medication does not contain a 'score' line and is intended to be eaten whole.
The medication has different packet sizes for specific weight ranges
If the brand produces a weight range for 'small dogs' and another for 'large dogs' it's always best to stick to the range that suits your pet.
Manufacturers provide a number of reasons why you shouldn't split medication that isn't scored with a clear line. These include:
f the medication doesn't contain a scored line, there is no guarantee that the medication will be evenly halved when you break it - no matter how careful you are. This increases the risk of over- or under-dosing.
Overdosing your pet can potentially lead to adverse affects, while underdosing can put your pet at risk of potentially fatal parasite infection.
Many drug manufacturers cannot guarantee that the active ingredient is evenly distributed throughout the inner core of the chew or tablet. So, even if you split a chew evenly, the amount of active ingredient may not be present in even amounts in each half.
This is particularly important with chews that contains more than one drug - for example, flea and worming combinations that contain one medication for fleas, and another for worming.
While in theory halving the tablet should provide your pet with an equal half of the medication, studies and tests have not been performed for most brands to prove even distribution.
Many medications are coated in a special layer, which slows the speed of drug release. If you break a medication's outer layer, you could be affecting the pharmacological properties. This has the potential to make the drug ineffective, or - worst case scenario - it may put your pet in danger.
There currently aren't any parasite preventatives designed for slow release, but this does prove a good point about how pharmacology is a complicated science, and why we should always follow to the advice of manufacturers!
In conclusion, while cost-saving and easier dosing are understandable motivations for splitting pet parasite prevention, it's crucial to prioritise your pet's health and safety. Manufacturers generally advise against splitting non-scored tablets or chews due to the risk of uneven dosing and potential alterations in drug release. Only scored tablets, those with explicit splitting instructions, or those specifically directed by a veterinarian should be divided. When in doubt, consulting your own veterinarian or our Vet Squad is always recommended to ensure your pet receives the correct and effective dosage of parasite prevention, safeguarding them from potential health risks.
Want to read more? Check out our other articles:
Which Flea or Worming Product Do I Need?
What is the Best Heartworm Treatment for Dogs?
Our experts continually monitor the health and wellness space and we update our articles when new information becomes available.
Veterinarian
Dr. Carla graduated from the University of Queensland in 2013 with a Bachelor of Veterinary Science and worked for a number of years in small animal clinics across South East Queensland. While Carla enjoys most facets of clinical veterinary work, she holds a special passion for feline medicine, pocket pets, and nutrition.
