Drontal for Cats: Side Effects and What to Expect
By Dr. Zubair Khalid, DVM, MS, PhD ·
Most Drontal for cats side effects are mild and short lived, such as drooling, vomiting, or soft stool in the first day after the tablet. Serious reactions are uncommon, but they can happen, so knowing what to watch for helps you act fast. This article is educational and is not a substitute for veterinary diagnosis or treatment.
Quick Answer
- Drooling, lip smacking, and one or two episodes of vomiting shortly after the pill are the most likely reactions, and they often pass within hours.
- Diarrhea or softer stool can show up in the first day or two and usually settles on its own.
- Never give a dose based on a guess. Your veterinarian calculates the dose from your cat's weight and health.
- Do not split, crush, or hide the tablet in a full meal unless your vet tells you to. Giving it on an empty stomach or with a small treat can reduce drooling and vomiting.
- Call your veterinarian the same day if your cat vomits the dose, seems wobbly, or will not eat. Call an emergency clinic right away for collapse, tremors, or trouble breathing.
What Drontal Is and What Veterinarians Use It For
Drontal is a deworming tablet. In cats it is used to treat common intestinal worms, especially roundworms and tapeworms. The active ingredients in the Drontal family include febantel, praziquantel, and pyrantel pamoate [1]. Praziquantel is the ingredient that targets tapeworms, and it appears in many feline parasite products because it works well and is generally well tolerated [2].
Veterinarians prescribe Drontal when a fecal test or the cat's history points to worms. Kittens, cats that hunt, cats with fleas, and cats that go outdoors are common candidates. Tapeworms in particular are tied to fleas, so treating the worms without controlling fleas often means the worms come back.
Deworming is not a one and done event. Many cats need a repeat dose, and some need a different product depending on which worms are present. Your veterinarian decides the plan based on your cat's age, weight, lifestyle, and test results.
How Drontal Works
The ingredients attack worms in different ways. Praziquantel damages the tapeworm's outer layer so the worm loses its grip and is passed in the stool. Pyrantel pamoate paralyzes roundworms so they detach from the intestinal wall and leave the body. Febantel interferes with the worm's energy use.
Because the drugs act on the worms and not on your cat's nervous system, most side effects come from the stomach and gut instead of the brain. That is why vomiting, drooling, and loose stool are the reactions owners notice most.
One interesting finding from dog research is that worm infections themselves change the gut bacteria, and deworming shifts that balance back toward a healthier mix [1]. That study looked at dogs, so it does not prove the same thing happens in cats, but it supports the idea that treating worms helps the gut overall.
Dosing Basics for Cats
Who decides the dose
Your veterinarian does. The dose depends on your cat's body weight and the specific product, and it is not the same for every cat. Do not use a dog product on a cat, and do not borrow a dose from another pet. Weight based dosing matters because too little may not kill the worms and too much raises the risk of side effects.
How to give the tablet
- Give the tablet by mouth, following your veterinarian's instructions.
- You can offer a small amount of food or a treat right after the pill to help it go down and reduce drooling.
- Do not crush the tablet into a full bowl of food unless your vet says it is fine. If your cat eats only part of the meal, the dose is incomplete.
- If your cat fights pills, ask your veterinarian about a pill popper or a compounded option.
- Watch your cat for about 30 minutes after dosing so you can see whether the pill stays down.
Missed dose
If you miss a dose, call your veterinarian for guidance instead of doubling up. Giving two doses close together raises the chance of vomiting and other side effects. Your vet will tell you whether to give the missed dose late or wait for the next scheduled one.
Drontal for Cats Side Effects: What Is Normal and What Is Not
Most reactions are mild and short. The table below separates the everyday stuff from the warning signs. If you are also managing other medications, our guide to cat allergy medication side effects explains how to tell a drug reaction from a flare of the original problem.
| Side effect | How common or serious | What to do |
|---|---|---|
| Drooling, lip smacking, foaming at the mouth | Common and usually mild. Often from the bitter taste of the tablet. | Wipe the mouth, offer water or a small treat. It usually stops within minutes to an hour. |
| Vomiting once or twice soon after the pill | Fairly common and usually mild. | Withhold food for an hour, then offer small amounts of water. Call your vet if it keeps happening or if you cannot tell whether the pill stayed down. |
| Diarrhea or soft stool | Uncommon to fairly common, usually mild. | Keep water available. Call your vet if it lasts more than a day or comes with blood, pain, or lethargy. |
| Poor appetite for a few hours | Mild and short lived. | Offer a small bland meal later. Call your vet if your cat refuses food for more than 24 hours. |
| Sleepiness or mild wobbliness | Uncommon. | Keep your cat indoors and watch closely. Call your vet if it does not improve within a few hours. |
| Tremors, twitching, or trouble walking | Rare but serious. | Treat as an emergency. Call your veterinarian or a pet poison control line right away. |
| Collapse, seizures, or trouble breathing | Rare and serious. | Go to an emergency clinic immediately. |
| Swelling of the face, hives, or severe itching | Rare and serious. | This can be an allergic reaction. Seek emergency care now. |
A few notes on the table. Drooling is often blamed on the drug when it is really the taste. Praziquantel has a bitter flavor, and cats foam at the mouth when they taste something bitter. That reaction looks dramatic but is usually harmless.
Vomiting is the side effect owners ask about most. If your cat vomits within an hour of the dose, the medicine may not have been absorbed. Do not give another tablet on your own. Call your veterinarian, who can decide whether to redose or switch products.
Diarrhea after deworming can also reflect the worms leaving the body, not just the drug. Either way, mild loose stool for a day is not a reason to panic. Bloody diarrhea, repeated vomiting, or a cat that stops eating is.
Is Drontal Safe for Cats?
For most healthy adult cats, Drontal is considered safe when it is dosed correctly by a veterinarian. Praziquantel, one of its main ingredients, has a long track record in feline parasite treatment and is well tolerated in topical combination products studied in cats [2][3]. Those studies looked at topical products instead of Drontal tablets, so they support the safety of the ingredient, not the exact tablet.
Safety depends on the individual cat. Age, weight, pregnancy status, liver health, and other medications all matter. Kittens and very small cats are more sensitive, and a dose that is fine for a ten pound cat may be too much for a two pound kitten.
If your cat has had a bad reaction to a dewormer before, tell your veterinarian before the next dose. There is often an alternative product.
Who Should Not Take Drontal and What Interacts With It
Drontal is not right for every cat. Your veterinarian may avoid it or choose a different product if your cat:
- Is pregnant or nursing, unless your vet specifically approves it
- Is a very young kitten below the age or weight your vet sets for safe use
- Has liver disease or another serious ongoing illness
- Has had an allergic reaction to any ingredient in the product
- Is already taking another dewormer, because stacking products can raise the risk of side effects
Drug interactions are not well established for every combination, so the safest step is to give your veterinarian a full list of everything your cat takes. That includes prescription drugs, over the counter products, flea and tick treatments, and supplements. If your cat takes gabapentin or a seizure medication, ask your vet about timing and interactions. Our articles on gabapentin side effects in cats and seizure medication side effects in cats cover what those drugs can do on their own, which helps you sort out what is causing a new symptom.
Overdose and When to Call for Help
An overdose can happen when a cat gets a dog tablet, when two doses are given too close together, or when a cat eats the package. Signs to watch for include heavy drooling, repeated vomiting, tremors, wobbliness, and lethargy. Severe cases can involve seizures.
If you think your cat got too much, do not wait for symptoms. Call your veterinarian or a pet poison control hotline right away. Have the product name, the strength, the number of tablets, and your cat's weight ready. Do not try to make your cat vomit unless a veterinarian tells you to.
Limitations and When to Contact a Veterinarian
No article can tell you what is happening with your specific cat. Individual cases need a veterinarian who can examine your cat, ask questions, and run tests if needed.
Call your veterinarian the same day if:
- Your cat vomits the dose within an hour and you are unsure whether the medicine stayed down
- Vomiting happens more than twice, or continues past a few hours
- Diarrhea lasts more than a day, or contains blood
- Your cat refuses food or water for more than 24 hours
- Your cat seems unusually tired, wobbly, or withdrawn
- You see drooling that does not stop
Go to an emergency clinic now if:
- Your cat collapses or cannot stand
- You see tremors, twitching, or a seizure
- Breathing becomes fast, noisy, or labored
- The face, muzzle, or throat swells
- Your cat is unresponsive or hard to wake
For a routine visit, call during normal hours if the worms are still visible in the stool after treatment, if your cat keeps getting worms, or if you have questions about the next dose. Repeat infections often mean fleas or another source is still in the picture.
Frequently Asked Questions
How long do Drontal side effects last in cats?
Most mild reactions, like drooling and a single vomit, pass within a few hours. Loose stool may take a day or two to settle. If anything lasts longer than that, or gets worse instead of better, call your veterinarian.
Can I give Drontal to my cat on an empty stomach?
Follow your veterinarian's instructions, since product directions can differ. Many owners find that a small treat right after the pill reduces drooling and helps the tablet go down. Do not hide the pill in a large meal, because a half eaten meal means a partial dose.
What should I do if my cat vomits after taking Drontal?
Do not give another tablet on your own. Call your veterinarian and describe when the vomiting happened and whether you saw the pill come back up. Your vet will decide whether the dose needs to be repeated or whether a different dewormer is a better fit.
Is Drontal safe for kittens?
Not every kitten is a candidate, and the decision depends on age, weight, and overall health. Your veterinarian sets the dose and timing for kittens. Never use a dose meant for an adult cat or a dog on a kitten.
Can Drontal cause diarrhea in cats?
Yes, loose stool is a possible side effect, and it is usually mild and brief. Keep fresh water available and watch for blood, pain, or a cat that stops eating. Call your veterinarian if diarrhea lasts more than a day or comes with other signs.
Related Articles
- Cat Allergy Medication Side Effects: What to Watch For
- What Are the Side Effects of Apoquel for Cats?
- Cat Urinary Tract Infection Side Effects
- What Are the Side Effects of Seizure Medication in Cats?
- What Are the Side Effects of Gabapentin for Cats?
- Cat Bad Breath and Drooling: When to See the Vet
- Drontal for Cats: Dosage, Schedule, and How Often
- Cat Deworming Side Effects: What to Expect
- Pyrantel for Cats: Side Effects and What to Watch For
References
- Regulation Effect of Toxocara canis and Anthelmintics on Intestinal Microbiota Diversity and Composition in Dog. Microorganisms, 2024.
- Efficacy of a single-dose topical formulation combining Fipronil, Moxidectin and Praziquantel against natural infestations of Notoedres cati, Otodectes cynotis and Felicola subrostratus in cats. Revista brasileira de parasitologia veterinaria = Brazilian journal of veterinary parasitology : Orgao Oficial do Colegio Brasileiro de Parasitologia Veterinaria, 2026.
- Field evaluation of a topical combination of ivermectin, imidacloprid, and praziquantel for flea control in cats under routine clinical. Frontiers in parasitology, 2026.