Credelio Quattro for Dogs: Uses, Dosing, and Safety

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-09-20

Credelio Quattro is a prescription-only, flavored chewable tablet for dogs that combines four active ingredients in a single monthly dose: lotilaner, moxidectin, pyrantel pamoate, and praziquantel. It is labeled to kill adult fleas and several tick species, prevent heartworm disease, and treat and control a defined list of intestinal worms, including roundworms, hookworms, and tapeworms. It is given by mouth with food, once a month, and it is intended for dogs only. The label specifies a minimum age of 8 weeks and a minimum body weight of 1.5 kg (about 3.3 lb) [1]. This article explains what each ingredient does, which parasites the product covers, how the weight-band dosing works, and which dogs should not receive it.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

At a Glance

What Credelio Quattro Is and Who It Is For

Credelio Quattro is a systemic endectocide. That term means the drug is absorbed into the bloodstream after the dog swallows it, and it then works against both external parasites (ectoparasites such as fleas and ticks) and internal parasites (endoparasites such as heartworm and intestinal worms). The combination of four actives in one tablet is designed to cover the parasites that veterinarians most commonly target with monthly prevention in dogs.

The product belongs to a category veterinarians call combination monthly preventives. Before products like this existed, owners often had to give one medication for fleas and ticks, a second for heartworm prevention, and a third for intestinal deworming. Credelio Quattro consolidates those jobs into a single chew given once a month.

The label population is healthy dogs and puppies at least 8 weeks old and at least 1.5 kg. The field study supporting the heartworm prevention claim enrolled client-owned dogs 8 weeks of age and older weighing at least 1.5 kg from 13 geographically diverse veterinary clinics across the United States [1]. That study design reflects the real-world population the product is intended for.

Credelio Quattro is not a treatment for an existing adult heartworm infection. It is a heartworm preventive. Giving a preventive to a heartworm-positive dog is a distinct clinical situation, and the manufacturer studied that scenario specifically to confirm the product is well tolerated in dogs with patent infections [4]. The decision about when to start or continue a preventive in a heartworm-positive dog belongs to the veterinarian.

The Four Active Ingredients

Each tablet contains four drugs. Understanding what each one does helps explain the coverage table and the safety profile.

Lotilaner

Lotilaner is an isoxazoline. Isoxazolines are a class of insecticide and acaricide that act on the nervous system of fleas and ticks. Lotilaner is the flea and tick component of Credelio Quattro and is also the sole active ingredient in the single-agent product Credelio [2][5][6]. In the Credelio Quattro studies, lotilaner was tested both as part of the combination and on its own to confirm that the other ingredients do not interfere with its flea and tick activity [2]. Lotilaner is given at a minimum effective dose of 20 mg/kg in the combination product [1][7].

Moxidectin

Moxidectin is a macrocyclic lactone. It is the heartworm preventive component and also contributes to the intestinal nematode (roundworm and hookworm) activity of the product. The minimum effective dose in Credelio Quattro is 0.02 mg/kg [1][7]. Because moxidectin is a macrocyclic lactone, the manufacturer was required to test the product in dogs with the MDR1 gene mutation, a population that is more sensitive to this drug class [8]. That study is discussed in the safety section.

Pyrantel Pamoate

Pyrantel pamoate is a classic anthelmintic used against intestinal nematodes. In Credelio Quattro it targets roundworms and hookworms, and it works alongside moxidectin. The minimum effective dose is 5 mg/kg [1][7]. Pyrantel pamoate has a long history of use in dogs and is the same active ingredient found in many standalone dewormers.

Praziquantel

Praziquantel is the tapeworm component. It is active against cestodes (tapeworms), including the Echinococcus species that carry zoonotic importance [9]. The minimum effective dose in Credelio Quattro is 5 mg/kg [1][7]. Praziquantel is the reason Credelio Quattro covers tapeworms, a group that the flea and heartworm ingredients do not address.

Parasite Coverage

The table below summarizes the parasites Credelio Quattro is studied and labeled to cover, with the tick species named where the studies specified them.

What the Coverage Means in Practice

The flea and tick claims are built on laboratory infestation studies. In the pivotal flea and tick study, dogs were infested with 100 adult fleas and 50 adult brown dog ticks at set intervals, and live parasite counts were taken after treatment [2]. This is how efficacy is measured for regulatory purposes. The numbers show that a single dose keeps killing newly acquired fleas and ticks for a month.

The heartworm claim rests on a different kind of evidence. In the laboratory studies, dogs were inoculated with 50 D. immitis L3 larvae and then dosed, with efficacy judged by counting adult heartworms at necropsy roughly 150 days after inoculation [1]. The field study followed client-owned dogs for 11 consecutive monthly treatments [1]. Together these designs support the preventive claim.

The intestinal worm claims come from controlled infection studies. For roundworms, six studies evaluated immature adult and adult T. canis and adult T. leonina, with efficacy at or above 97% against the target stages and fecal egg count reduction measured 10 days after treatment [7]. For hookworms, nine laboratory studies covered fourth-stage larvae, immature adults, and adults of A. caninum plus adult U. stenocephala [12]. A separate multicenter field study in the United States measured a 99.9% reduction in A. caninum eggs per gram 10 days after treatment [11].

What Credelio Quattro Does Not Cover

Credelio Quattro is not a treatment for adult heartworm infection. It prevents the disease by killing the larval stages the mosquito transmits, before they mature into adult worms. A dog that already has adult heartworms needs a different treatment plan managed by a veterinarian.

The product does not treat flea tapeworm (Dipylidium caninum) as a named claim in the studies cited here. The tapeworm coverage documented in the studies centers on Echinococcus species [9]. If your dog has a tapeworm infection, your veterinarian will identify the species and confirm whether the product's label covers it.

Credelio Quattro does not treat mites, lice, or the protozoal parasites that cause diseases such as coccidiosis or giardiasis. It also does not repel fleas and ticks. It kills them after they get on the dog and take a blood meal. Because it works systemically, fleas and ticks must bite before they die, which is why speed of kill matters for reducing disease transmission risk [3][10].

How Credelio Quattro Works

Each active ingredient has a different target in the parasite.

Lotilaner blocks chloride channels in the nervous system of fleas and ticks. This disrupts normal nerve signaling and kills the parasite. Isoxazolines act quickly, and the speed studies show that lotilaner produces measurable tick kill within hours of dosing. In one comparison, lotilaner was the only product among three tested that significantly reduced an existing Ixodes scapularis infestation by 8 hours after treatment [3]. In a lone star tick comparison, lotilaner reduced Amblyomma americanum counts by 12 hours after treatment, and at 24 hours its efficacy was 95.3% [10].

Moxidectin interferes with chloride channels in the nervous system of nematodes and heartworm larvae. It is absorbed systemically and persists long enough to kill heartworm larvae acquired during the month after dosing. It also contributes to the roundworm and hookworm activity.

Pyrantel pamoate acts as a depolarizing neuromuscular blocker in susceptible worms. It causes spastic paralysis, and the paralyzed worms are expelled from the gut. It targets roundworms and hookworms.

Praziquantel damages the tegument (outer surface) of tapeworms, which leads to parasite death and elimination. It is the tapeworm-specific component.

Because the drugs have different mechanisms and different target parasites, combining them does not reduce the activity of any single component. The manufacturer ran specific non-interference studies to confirm this. In the flea and tick study, a lotilaner-only group was included to show the combination performed as expected [2]. In the tapeworm studies, groups receiving praziquantel alone or lotilaner alone were included to confirm the other ingredients did not interfere with praziquantel [9]. Similar non-interference work was done in the hookworm studies [12].

Dosing by Weight Band

Credelio Quattro is dosed by body weight. The label provides fixed-strength chewable tablets, and the dog receives the tablet strength that matches its weight band. The target dose range at the upper end of the recommended range is 20 to 41 mg/kg lotilaner, 0.02 to 0.04 mg/kg moxidectin, 5 to 10 mg/kg praziquantel, and 5 to 10 mg/kg pyrantel [13]. The minimum effective doses used in the efficacy studies were 20 mg/kg lotilaner, 0.02 mg/kg moxidectin, 5 mg/kg praziquantel, and 5 mg/kg pyrantel [1][7][9].

Dosing must follow the label weight bands. There is no off-label dose to calculate at home, and the tablet should not be split or combined in a way that does not match the label. If a dog's weight falls near a band boundary, the veterinarian confirms the correct strength. Puppies grow, so the weight band can change between monthly doses, and the veterinarian will adjust the strength at recheck visits.

The tablet is given with food. In the efficacy and safety studies, treatment was administered in a fed state [2][5][13]. Giving the chew with a meal supports absorption and matches the conditions under which the product was tested.

Treatment is repeated every 28 days (monthly). In the long-term safety study, dogs received treatment every 4 weeks on nine occasions [13]. In the heartworm field study, dogs received 11 consecutive monthly treatments [1]. The monthly interval is what maintains continuous coverage.

How to Give Credelio Quattro

Credelio Quattro is a flavored chewable tablet, and the studies describe it as palatable. The practical steps are straightforward.

1. Confirm the correct tablet strength for your dog's current weight.
2. Give the chew with food, ideally as part of a meal or immediately after eating.
3. Watch to make sure the dog swallows the tablet. If the dog spits it out or vomits soon after dosing, contact your veterinarian for guidance on whether to redose.
4. Record the date so the next monthly dose stays on schedule.
5. Keep the product out of reach of children and other animals.

If your dog is a picky eater, ask your veterinarian about the best way to offer the chew. Do not crush or mix the tablet into a large amount of food if the dog might not finish the whole portion, because the full dose needs to be consumed.

Side Effects and Safety

Credelio Quattro was evaluated in a dedicated safety program that included healthy dogs, MDR1-mutant dogs, heartworm-positive dogs, and long-term repeat dosing. The overall picture is that the product is well tolerated when used as labeled.

Gastrointestinal Upset

The most common adverse effects in the safety studies were gastrointestinal. In the heartworm-positive dog study, emesis occurred in the group receiving three times the maximum labeled dose, and diarrhea was observed across groups at various times [4]. Vomiting and diarrhea are the effects owners are most likely to notice. Mild, transient GI signs after dosing are common with oral parasite preventives. Persistent vomiting, bloody diarrhea, or a dog that refuses to eat needs veterinary attention.

Lethargy

Reduced activity or lethargy can occur after dosing. In most cases this is mild and short-lived. A dog that becomes profoundly lethargic, weak, or unresponsive needs to be seen promptly.

Neurologic Signs in Isoxazoline-Sensitive Dogs

Isoxazolines as a class have been associated with neurologic adverse effects in some dogs. A large survey of dog owners and veterinarians examined isoxazoline use and reported that neurologic effects, including seizures, were among the serious adverse events reported [14]. This does not mean most dogs have problems. It means a small number of dogs are sensitive to the class, and those dogs can develop signs such as tremors, ataxia (wobbliness), or seizures. If your dog has a history of neurologic disease or has reacted to an isoxazoline before, tell your veterinarian before starting Credelio Quattro.

The MDR1 (ABCB1) Breed Caution

Moxidectin is a macrocyclic lactone. Dogs with the MDR1 gene mutation have reduced or absent P-glycoprotein at the blood-brain barrier. P-glycoprotein normally pumps certain drugs, including macrocyclic lactones, out of the brain. Without it, these drugs can accumulate in the central nervous system and cause neurotoxicity [8].

Because of this, the manufacturer tested Credelio Quattro specifically in homozygous MDR1-mutant Collie dogs. In that study, 32 dogs were divided into four groups receiving placebo, 1x, 2x, or 5x the maximum labeled dose on three consecutive occasions 28 days apart. The dogs were monitored for avermectin-sensitive signs including seizures, ataxia, depression, mydriasis, muscle tremors, and salivation or vomiting. The safety assessment was based on these scores plus general health, body weight, and clinical measures [8]. The study was designed to establish whether the product is safe in this sensitive population.

The practical takeaway for owners is that breeds and lines known to carry the MDR1 mutation (Collies and related herding breeds among them) should be identified to the veterinarian. If your dog is a known MDR1-mutant or you do not know the status and your breed is at risk, your veterinarian will factor that into the decision. Do not assume a product is unsafe for your dog based on breed alone, and do not assume it is safe without discussing the mutation status with your veterinarian.

Long-Term Safety

A long-term study followed healthy Beagle dogs from 8 weeks of age into adulthood, dosing them every 4 weeks for nine treatments at 1x, 3x, or 5x the maximum dose. Safety was assessed through health observations, complete physical and neurologic examinations, food consumption, clinical pathology (hematology, clinical chemistry, urinalysis), body weight, and macroscopic and microscopic tissue examinations. Credelio Quattro did not induce serious treatment-related adverse effects in that study [13].

Safety in Heartworm-Positive Dogs

Dogs with existing adult heartworm infections were studied because rapid death of microfilariae or adult worms can cause serious reactions. In that study, dogs with surgically implanted adult heartworms were dosed at 1x or 3x the maximum labeled dose on three consecutive monthly occasions. The product was well tolerated, with emesis in the high-dose group and diarrhea observed across groups [4]. This study supports the safety of the product in heartworm-positive dogs, but it does not change the fact that a heartworm-positive dog needs a treatment plan for the infection itself.

Which Dogs Should Not Receive Credelio Quattro

The label sets a minimum age of 8 weeks and a minimum weight of 1.5 kg [1]. Dogs below either threshold should not receive the product.

Dogs with a known hypersensitivity to any of the four active ingredients should not receive it. Because the product contains a macrocyclic lactone, dogs with the MDR1 mutation require a specific risk-benefit discussion with the veterinarian, guided by the dedicated safety study in that population [8].

Credelio Quattro is for dogs only. It should not be given to cats or other species.

Dogs that are pregnant, breeding, or lactating are a separate category. The studies cited here were conducted in young healthy dogs, MDR1-mutant dogs, and heartworm-positive dogs, not in breeding animals. If your dog is pregnant or being used for breeding, your veterinarian will weigh the options.

Interactions and Precautions

Because Credelio Quattro contains a macrocyclic lactone, the main interaction concern is with other drugs that affect the same pathways or add to neurologic risk. The MDR1 study exists precisely because moxidectin is a P-glycoprotein substrate [8]. If your dog is receiving other medications, including other parasite preventives, tell your veterinarian so the combination can be reviewed.

Do not give Credelio Quattro at the same time as another product that contains the same active ingredients. Doubling up on lotilaner, moxidectin, pyrantel, or praziquantel is not appropriate. Many heartworm and flea products overlap in their ingredients, and your veterinarian can confirm which combination is safe.

If your dog is scheduled for a heartworm test, the timing matters. Heartworm preventives are typically started after a negative test in dogs old enough to be tested, and the veterinarian will follow the standard testing schedule for your dog's age and history.

How Credelio Quattro Compares With Other Options

Credelio Quattro sits in the same broad category as other monthly oral combination products. The closest comparison in the studies cited here is Simparica Trio, which contains moxidectin, sarolaner, and pyrantel. It was used as the positive control in the Credelio Quattro heartworm field study [1] and as the control product in the gastrointestinal nematode field study [11]. The key structural difference is that Credelio Quattro adds praziquantel, which is the tapeworm component, and uses lotilaner instead of sarolaner for flea and tick control.

Other isoxazoline products include afoxolaner (NexGard) and fluralaner (Bravecto). Speed-of-kill studies have compared lotilaner against sarolaner and afoxolaner for specific tick species. For Ixodes scapularis, lotilaner was the only product that significantly reduced an existing infestation by 8 hours after treatment, and all treated groups had significantly lower tick counts than untreated dogs from 24 hours onward [3]. For Amblyomma americanum, lotilaner and afoxolaner both outperformed sarolaner at 24 hours post-treatment [10].

The practical comparison for owners comes down to coverage. A product that includes praziquantel covers tapeworms. A product without it does not. A product that includes moxidectin covers heartworm. A flea-and-tick-only product does not. Credelio Quattro is designed as an all-in-one monthly option, which reduces the number of separate medications an owner has to manage.

Questions to Ask Your Veterinarian

Before starting Credelio Quattro, these questions help tailor the decision to your dog.

1. Is my dog at or above the label minimums of 8 weeks and 1.5 kg?
2. Does my dog's breed or line carry the MDR1 mutation, and should we test for it?
3. Has my dog had a neurologic reaction to any parasite preventive before?
4. Is my dog currently heartworm-negative, and when was the last test?
5. Does my dog need tapeworm coverage based on its lifestyle and exposure risk?
6. Which tablet strength matches my dog's current weight, and will that change as the puppy grows?
7. What should I do if my dog vomits right after taking the chew?
8. Are there other parasite preventives or medications my dog is taking that could interact?

Limitations and When to Contact a Veterinarian

This article describes the labeled uses, dosing framework, and safety profile of Credelio Quattro based on the studies cited. It cannot tell you whether the product is right for your individual dog. That decision depends on your dog's weight, age, health status, MDR1 status, heartworm test results, and other medications.

Contact a veterinarian promptly if any of the following occur after dosing:

• Vomiting that does not stop, or vomiting within a few hours of taking the chew
• Diarrhea that is bloody, severe, or lasts more than a day
• Lethargy that is pronounced or does not improve
• Tremors, wobbliness, stumbling, or a seizure
• Facial swelling, hives, or difficulty breathing
• Any sign that concerns you

Contact a veterinarian before the next dose if your dog's weight has changed enough to cross a tablet weight band, if your dog has been started on a new medication, or if you missed a monthly dose and need guidance on getting back on schedule.

Frequently Asked Questions

What is Credelio Quattro used for in dogs?

Credelio Quattro is a monthly prescription chewable tablet that kills adult fleas and several tick species, prevents heartworm disease, and treats and controls roundworms, hookworms, and tapeworms in dogs [2][1][7][12][9].

What are the four active ingredients in Credelio Quattro?

The four active ingredients are lotilaner (an isoxazoline for fleas and ticks), moxidectin (a macrocyclic lactone for heartworm and intestinal nematodes), pyrantel pamoate (for roundworms and hookworms), and praziquantel (for tapeworms) [1][7].

How is Credelio Quattro dosed?

It is dosed by body weight using fixed-strength chewable tablets, given by mouth with food once every 28 days. The label sets a minimum age of 8 weeks and a minimum weight of 1.5 kg [1][13].

Which ticks does Credelio Quattro cover?

The studies document activity against Rhipicephalus sanguineus, Ixodes scapularis, Haemaphysalis longicornis, and Amblyomma americanum [2][5][6][10].

Does Credelio Quattro prevent heartworm disease?

Yes. It prevents heartworm disease caused by Dirofilaria immitis, confirmed in two laboratory studies and one field study [1]. It does not treat existing adult heartworm infections.

Can Credelio Quattro be given to MDR1-mutant dogs?

The manufacturer studied the product specifically in homozygous MDR1-mutant Collie dogs at up to five times the maximum labeled dose to evaluate safety in this sensitive population [8]. Whether to use it in an individual MDR1-mutant dog is a decision for the veterinarian.

What are the most common side effects of Credelio Quattro?

The most common side effects reported in the safety studies were gastrointestinal, including vomiting and diarrhea, along with possible lethargy. Neurologic signs can occur in isoxazoline-sensitive dogs [4][14].

What should I do if my dog vomits after taking Credelio Quattro?

Contact your veterinarian for guidance. Vomiting soon after dosing can mean the full dose was not absorbed, and your veterinarian will advise whether the dose needs to be repeated.

Related Articles

• Anesthesia Machine Safety Checks for Laboratory Animal Use
• Prednisone for Dogs: Uses, Side Effects, and Safety Guidelines
• Pharmacotherapy in Avian Medicine
• Hypothyroidism in Dogs: Weight Gain, Lethargy and Thyroxine Dosing
• Can Cats Eat Valerian Root? Sedative Effect and Dosing
• Ferret Care: Insulinoma hypoglycemia diet and prednisone dosing
• Clonidine for Dogs: Uses, Dosing, and Safety
• Adequan for Dogs: Uses, Dosing, and Safety
• Pepcid for Dogs: Dosage, Uses, and Safety Guide

Sources

1. Efficacy of a novel chewable tablet (Credelio Quattro™) containing lotilaner, moxidectin, praziquantel, and pyrantel for the prevention of heartworm disease (Dirofilaria immitis) in dogs.
2. Efficacy of Credelio Quattro™ chewable tablets containing lotilaner, moxidectin, pyrantel, and praziquantel against Ctenocephalides felis and Rhipicephalus sanguineus infestations on dogs.
3. Comparative speed of kill of induced Ixodes scapularis infestations following treatment of dogs with endectocides containing either sarolaner (Simparica Trio™), afoxolaner (NexGard(®) PLUS), or lotilaner (Credelio Quattro™).
4. Safety of Credelio Quattro™ (lotilaner, moxidectin, praziquantel, and pyrantel chewable tablets) in dogs infected with adult heartworms (Dirofilaria immitis).
5. Efficacy of Credelio Quattro™ (lotilaner, moxidectin, praziquantel, and pyrantel chewable tablets) and Credelio™ (lotilaner) chewable tablets in the prevention of Borrelia burgdorferi transmission from infected Ixodes scapularis in dogs.
6. Efficacy of Credelio Quattro(™) (lotilaner, moxidectin, pyrantel, praziquantel) and Credelio(™) (lotilaner) against longhorned tick, Haemaphysalis longicornis,-induced infestations on dogs.
7. Efficacy of a novel chewable tablet (Credelio Quattro(™)) containing lotilaner, moxidectin, praziquantel, and pyrantel against Toxocara canis and Toxascaris leonina infections in dogs.
8. Safety of Credelio Quattro™ (lotilaner, moxidectin, praziquantel, and pyrantel chewable tablets) in homozygous MDR1-mutant collie dogs.
9. Efficacy of a novel chewable tablet (Credelio Quattro(™)) containing lotilaner, moxidectin, praziquantel, and pyrantel for the treatment and control of Echinococcus multilocularis and E. granulosus infections in dogs.
10. Comparative speed of kill provided by lotilaner (Credelio™), sarolaner (Simparica Trio™), and afoxolaner (NexGard™) to control Amblyomma americanum infestations on dogs.
11. Field efficacy and safety evaluation of a novel chewable tablet (Credelio Quattro™) containing lotilaner, moxidectin, praziquantel, and pyrantel against gastrointestinal nematode infections in dogs in the USA.
12. Efficacy of a novel chewable tablet (Credelio Quattro™) containing lotilaner, moxidectin, praziquantel, and pyrantel for the treatment and control of hookworm infections in dogs.
13. Long-term safety of Credelio Quattro™ (lotilaner, moxidectin, praziquantel, and pyrantel chewable tablets), a novel orally administered combination endectocide for dogs.
14. Survey of canine use and safety of isoxazoline parasiticides.