Q: Does NexGard treat ear mites?

Afoxolaner is not labeled for the treatment of ear mites (Otodectes cynotis), though it may have some off-label efficacy. Your veterinarian can recommend an appropriate product for ear mite treatment.

# NexGard Dose Calculator: Afoxolaner Flea Tick Dose by Weight ## Key Takeaways - The standard therapeutic dose of afoxolaner (NexGard®) for dogs is 2.5 mg per kilogram (mg/kg) of body weight, administered orally once monthly. - Accurate body weight measurement is paramount for correct dosing; never estimate weight, and consult a veterinarian for dogs exceeding 50 kg to determine appropriate tablet combinations. - Afoxolaner acts by blocking GABA-gated chloride channels in arthropod nerve cells, leading to rapid ectoparasite mortality, and has demonstrated efficacy against fleas, ticks, and myiasis-causing larvae. - While generally well-tolerated, isoxazolines, including afoxolaner, have been associated with neurological adverse events such as seizures, necessitating veterinary consultation for dogs with pre-existing neurological conditions. - NexGard® is approved for puppies 8 weeks of age and older weighing at least 2 kg (4.4 lbs) and is strictly for canine use; it is not approved for cats or other species. - Comprehensive parasite control involves year-round prevention with afoxolaner and concurrent environmental treatment to eliminate flea life stages (eggs, larvae, pupae) not present on the host. --- **Direct answer:** The standard target dose of afoxolaner (NexGard®) for dogs is **2.5 mg per kilogram (mg/kg) of body weight**, administered orally once monthly. Commercial NexGard® chewable tablets are manufactured in four size ranges to approximate this dose: 2.5–4 kg (11 mg), 4.1–10 kg (28 mg), 10.1–25 kg (68 mg), and 25.1–50 kg (136 mg). You must weigh your [dog](/knowledge/veterinary-medicine/clinical-methods/dog) accurately before administration. **Do not guess the dose.** This article provides a definitive, source-grounded guide to using an afoxolaner dose calculator, interpreting the label, and understanding the clinical evidence behind this isoxazoline parasiticide. **Owner Triage Summary:** If you are unsure which tablet size to give, stop and weigh your dog on a scale. Never split tablets between two dogs. If your dog weighs more than 50 kg, you must combine two tablets (e.g., a 136 mg tablet plus a 28 mg tablet) to achieve the correct mg/kg dose. If your dog has a history of seizures or neurological disease, consult your veterinarian before administering any isoxazoline product. If your dog vomits within 2 hours of dosing, contact your veterinarian before re-dosing. ## The Clinical Rationale for Weight-Based Dosing Afoxolaner is a systemic ectoparasiticide belonging to the isoxazoline class. It is available as a standalone product (NexGard®) and in combination with other antiparasitics (e.g., NexGard Spectra® with milbemycin oxime, or NexGard Plus® with moxidectin and pyrantel) [1][2]. The molecule works by blocking GABA-gated chloride channels in arthropod nerve cells, leading to rapid death of fleas and ticks. The therapeutic index of afoxolaner is wide, but the efficacy and safety profile are optimized at the label dose. The approved dose range is **2.5 to 6.3 mg/kg** for the chewable tablet, though the target is 2.5 mg/kg. Clinical studies confirm that a single oral dose of 2.5 mg/kg is effective against a broad spectrum of ectoparasites, including fleas (*Ctenocephalides felis*), ticks (e.g., *Ixodes ricinus*, *Rhipicephalus sanguineus*), and even specific myiasis-causing larvae [1][3][4]. A dose calculator is not a substitute for a scale, but it is a critical tool for verifying that the chosen tablet size matches the patient's weight. In human medicine, dose calculators have been shown to reduce medication errors, particularly in populations where weight-based dosing is mandatory, such as pediatrics [5]. The same logic applies in veterinary medicine: a calculator minimizes arithmetic errors when converting pounds to kilograms or when combining tablet sizes for giant breeds. ## At a Glance: NexGard® Tablet Selection Table This table provides the standard clinical decision framework for selecting the correct tablet size. **This is a reference tool, not a substitute for a veterinary prescription.** | Dog Weight (kg) | Dog Weight (lbs) | Tablet Strength (mg afoxolaner) | Approximate Dose (mg/kg) | | :--- | :--- | :--- | :--- | | 2.5 – 4.0 kg | 5.5 – 8.8 lbs | 11 mg | 2.75 – 4.4 mg/kg | | 4.1 – 10.0 kg | 9.0 – 22.0 lbs | 28 mg | 2.8 – 6.8 mg/kg | | 10.1 – 25.0 kg | 22.2 – 55.1 lbs | 68 mg | 2.72 – 6.7 mg/kg | | 25.1 – 50.0 kg | 55.3 – 110.2 lbs | 136 mg | 2.72 – 5.4 mg/kg | | > 50.0 kg | > 110.2 lbs | **Combination required** (e.g., 136 mg + 136 mg) | Must be calculated by vet | **Important Note:** The table above reflects the labeled weight bands. The actual mg/kg dose varies within these bands because the tablet strength is fixed. A 4.0 kg dog receiving the 11 mg tablet gets 2.75 mg/kg, while a 2.5 kg dog receiving the same tablet gets 4.4 mg/kg. Both are within the safe and effective range, but the dose is not perfectly linear. This is why accurate weighing is critical, especially for dogs near the boundaries of a weight band. ## How to Use the Afoxolaner Dose Calculator The calculation is simple, but the clinical decision requires context. Here is the step-by-step process. ### Step 1: Obtain an Accurate Body Weight Weigh the dog on a calibrated scale. Do not use a bathroom scale while holding the dog and subtracting your own weight unless the scale is digital and accurate to 0.1 kg. For small breeds, an error of 0.5 kg can shift the dog into a different dose band. For giant breeds, an error of 5 kg can lead to underdosing. ### Step 2: Calculate the Target Dose The target dose is **2.5 mg/kg**. The formula is: **Body Weight (kg) × 2.5 mg/kg = Target Dose (mg)** Example: A 20 kg dog requires 20 × 2.5 = 50 mg of afoxolaner. The closest tablet is the 68 mg tablet (for dogs 10.1–25 kg), which provides 3.4 mg/kg. This is within the approved range. ### Step 3: Select the Appropriate Tablet Size Use the table above to select the tablet size. If the dog's weight falls on the boundary (e.g., exactly 10.0 kg), choose the lower weight band tablet (28 mg) to avoid overdosing, unless your veterinarian advises otherwise. ### Step 4: Verify the Dose for Giant Breeds For dogs over 50 kg, a single tablet is insufficient. You must combine tablets to reach the target dose. For example, a 60 kg dog requires 150 mg of afoxolaner (60 × 2.5). This can be achieved by administering one 136 mg tablet and one 28 mg tablet (total 164 mg, providing 2.73 mg/kg). Always have your veterinarian calculate the exact combination for giant breeds. ## Evidence-Based Efficacy of Afoxolaner The efficacy of afoxolaner at the 2.5 mg/kg dose is supported by multiple controlled studies. It is not merely a label claim; it is a reproducible clinical outcome. ### Flea and Tick Control A large European field study evaluated the efficacy of NexGard® Spectra® (afoxolaner + milbemycin oxime) against natural flea and tick infestations. The study demonstrated that the product, administered at the label dose of 2.5 mg/kg afoxolaner, provided significant reductions in parasite counts on Days 14 and 30 post-treatment [1]. The speed of kill is rapid, which is essential for reducing the transmission of vector-borne pathogens. ### Treatment of Myiasis Afoxolaner has shown remarkable efficacy beyond fleas and ticks. A 2024 study demonstrated that a single oral dose of 2.5 mg/kg afoxolaner was 100% larvicidal against *Dermatobia hominis* (the human bot fly) larvae in naturally infested dogs, with all larvae found dead within 24 hours [3]. Similarly, a 2026 field study confirmed that a single dose of afoxolaner was 94% effective against *Cordylobia anthropophaga* (tumbu fly) myiasis on Day 15 and 100% effective by Day 30 [4]. These studies highlight the molecule's systemic distribution and potent activity against tissue-dwelling arthropods. ### Off-Label Use in Exotic Species While this article focuses on dogs, it is worth noting that afoxolaner has been evaluated in other species. A 2025 study investigated the use of oral afoxolaner at 2.5 mg/kg in captive-bred lizards for the treatment of mite infestations (*Ophionyssus natricis*). The study reported efficacy, but this is off-label use and should only be performed under the direct guidance of a veterinarian experienced in exotic animal medicine [6]. Do not attempt to dose reptiles or other non-canine pets with NexGard®. ### Comparative Efficacy Afoxolaner is often compared to other isoxazolines, such as sarolaner (Simparica Trio®). While both are effective, they are distinct molecules. A 2026 study compared Simparica Trio® (sarolaner, moxidectin, pyrantel) with NexGard® Plus (afoxolaner, moxidectin, pyrantel) against a macrocyclic lactone-resistant *Dirofilaria immitis* isolate. Both products provided high efficacy (98.1% for NexGard Plus vs. 99.5% for Simparica Trio) against adult heartworms, but the study noted that the moxidectin dose in Simparica Trio was higher, which may be relevant in areas with resistant heartworm [2]. This study does not suggest that afoxolaner is inferior; it simply illustrates that product selection depends on the specific parasite spectrum and regional resistance patterns. ## Safety Profile and Adverse Effects Afoxolaner is generally well-tolerated in dogs. The most commonly reported adverse events in clinical trials and post-marketing surveillance are mild and transient. ### Common Adverse Events - Vomiting - Diarrhea (or diarrhoea) - Lethargy - Decreased appetite - Pruritus (itching) These signs are usually self-limiting and resolve within 24 to 48 hours. Administering the dose with food can reduce the likelihood of gastrointestinal upset. ### Neurological Concerns The isoxazoline class, including afoxolaner, has been associated with neurological adverse events in some dogs. These can include muscle tremors, ataxia (incoordination), and seizures. The United States Food and Drug Administration (FDA) has issued a class warning for isoxazolines. **Dogs with a history of seizures or neurological disorders should only receive afoxolaner under strict veterinary supervision.** The mechanism is related to the drug's action on GABA-gated channels, which, while selective for insects, can have off-target effects in mammals at high doses or in susceptible individuals. ### Contraindications - **Puppies:** NexGard® is approved for puppies 8 weeks of age and older, weighing at least 2 kg (4.4 lbs). - **Breeding Animals:** The safety of afoxolaner has not been fully established in breeding, pregnant, or lactating dogs. Use only when the potential benefit outweighs the risk, as determined by your veterinarian. - **Hypersensitivity:** Dogs with a known hypersensitivity to afoxolaner or any other ingredient in the product should not receive it. ## Pharmacology and Mechanism of Action Afoxolaner is a systemic insecticide and acaricide. After oral administration, it is absorbed into the bloodstream and distributed throughout the body. When a flea or tick bites the dog, it ingests a lethal dose of afoxolaner. ### Pharmacokinetics - **Onset of Action:** Afoxolaner begins killing fleas within 4 hours of administration, with peak efficacy within 24 hours. - **Duration:** A single dose provides persistent efficacy for at least 30 days, which is why monthly administration is recommended. - **Metabolism:** Afoxolaner is metabolized in the liver and excreted in the bile and feces. ### Spectrum of Activity Afoxolaner is effective against: - **Fleas:** *Ctenocephalides felis*, *Ctenocephalides canis* - **Ticks:** *Ixodes scapularis*, *Dermacentor variabilis*, *Rhipicephalus sanguineus*, *Amblyomma americanum* - **Mites:** *Sarcoptes scabiei*, *Demodex canis* (often used off-label for demodicosis) - **Lice:** *Heterodoxus spiniger* (chewing lice) [7] - **Myiasis-causing larvae:** *Dermatobia hominis*, *Cordylobia anthropophaga* [3][4] ## Regional Considerations for Flea and Tick Control The choice of ectoparasiticide should be guided by the regional prevalence of specific parasites and vector-borne diseases. ### North America In the United States and Canada, the primary tick vectors include the black-legged tick (*Ixodes scapularis*), the American dog tick (*Dermacentor variabilis*), and the Lone Star tick (*Amblyomma americanum*). These ticks transmit diseases such as Lyme disease, anaplasmosis, and ehrlichiosis. Monthly afoxolaner administration is a cornerstone of prevention, particularly in endemic areas. ### Europe In Europe, the castor bean tick (*Ixodes ricinus*) and the brown dog tick (*Rhipicephalus sanguineus*) are the most common species. The European Scientific Counsel for Companion Animal Parasites (ESCCAP) guidelines emphasize year-round protection. Afoxolaner is widely used across Europe, including in combination products like NexGard Spectra® [1][8]. ### Australia and New Zealand Australia has unique tick species, most notably the paralysis tick (*Ixodes holocyclus*), which can cause fatal ascending paralysis in dogs. The brown dog tick is also prevalent. While afoxolaner is effective against these ticks, the risk of tick paralysis requires rapid tick removal and veterinary intervention if clinical signs develop. Always consult local guidelines, as the Australian Veterinary Association (AVA) and state authorities may have specific recommendations for tick control in high-risk areas. ### Tropical Regions In Central and South America, the human bot fly (*Dermatobia hominis*) is a significant cause of furuncular myiasis in dogs. The 2024 study confirming afoxolaner's larvicidal efficacy is particularly relevant for veterinarians practicing in these regions [3]. ## Veterinary Examination and Diagnostics Before prescribing afoxolaner, a veterinarian will typically perform a thorough physical examination. This is not just to confirm the dog's weight, but to assess overall health and identify any contraindications. ### Key Diagnostic Steps 1. **Weight Measurement:** Accurate body weight is the single most important factor in dose calculation. 2. **Skin and Coat Examination:** To assess the severity of flea or tick infestation, check for signs of flea allergy dermatitis (FAD), and look for secondary skin infections. 3. **History:** The veterinarian will ask about the dog's medical history, including any history of seizures, liver disease, or drug reactions. 4. **Fecal Examination:** If [intestinal parasites](/knowledge/parasites/pet-parasites/intestinal-parasites-dogs-cats-identification-treatment) are suspected, a fecal flotation may be performed, as afoxolaner does not treat internal parasites (unless combined with other active ingredients). ## Evidence-Based Management and Prevention The use of afoxolaner should be part of a comprehensive parasite control program. ### Year-Round Prevention The Companion Animal Parasite Council (CAPC) recommends year-round administration of broad-spectrum parasiticides. This is because fleas can survive indoors during winter, and ticks can be active whenever temperatures are above freezing. Monthly administration of afoxolaner ensures continuous protection. ### Environmental Control While afoxolaner kills fleas on the dog, it does not kill flea eggs, larvae, or pupae in the environment. To eliminate an existing infestation, you must treat the environment. This includes: - Washing all pet bedding in hot water. - Vacuuming carpets, rugs, and upholstery thoroughly and disposing of the vacuum bag. - Using an environmental flea spray or fogger containing an insect growth regulator (IGR), such as pyriproxyfen or methoprene. ### Combination Products If your dog is also at risk for heartworm disease or intestinal parasites, your veterinarian may recommend a combination product. NexGard Spectra® (afoxolaner + milbemycin oxime) provides protection against fleas, ticks, heartworms, and intestinal parasites [1][9]. NexGard Plus® (afoxolaner + moxidectin + pyrantel) offers similar coverage [2]. The choice between these products depends on the specific parasite risks in your area and your dog's lifestyle. ## Unsafe Home Remedies and What to Avoid There are many dangerous home remedies for flea and tick control that should never be used on dogs. - **Garlic and Brewer's Yeast:** There is no scientific evidence that these are effective, and garlic can cause hemolytic anemia in dogs. - **Essential Oils:** Tea tree oil, eucalyptus, and other essential oils are toxic to dogs, especially when applied topically or ingested. - **Permethrin (Dog-Only Products):** While safe for dogs, permethrin is highly toxic to cats. Never use a dog-specific permethrin product on a [cat](/knowledge/veterinary-medicine/clinical-methods/cat). - **Dish Soap:** While it can kill fleas on contact, it does not provide residual protection and can strip the skin of natural oils, causing dryness and irritation. - **Human Flea Products:** Never use a flea product intended for humans on a dog. ## Prognosis and Expected Outcomes The prognosis for dogs treated with afoxolaner is excellent. In clinical trials, a single dose rapidly eliminates existing flea and tick infestations. For myiasis, the larvicidal effect is observed within 24 hours [3][4]. Clinical signs associated with infestations, such as pruritus and dermatitis, typically resolve within 1 to 2 weeks as the skin heals. ## Limitations and When to Contact a Veterinarian This article provides general guidelines, but it cannot predict how an individual dog will respond to therapy. Breed-level information cannot predict the occurrence of rare adverse events like seizures. The dose calculator is a tool, not a diagnostic instrument. **Contact your veterinarian immediately if you observe any of the following after administering afoxolaner:** - **Seizures, tremors, or ataxia (wobbliness)** - **Vomiting or diarrhea (diarrhoea) lasting more than 24 hours** - **Lethargy or extreme weakness** - **Facial swelling or hives (signs of an allergic reaction)** - **Difficulty breathing** If you are unsure about the correct dose, or if your dog falls outside the standard weight bands (e.g., under 2 kg or over 50 kg), do not guess. Contact your veterinarian for a specific dosing plan. ## Frequently Asked Questions ### 1. What is the exact dose of NexGard for my dog? The target dose is 2.5 mg of afoxolaner per kilogram of body weight. You must weigh your dog and select the tablet size that corresponds to your dog's weight band, as shown in the table above. ### 2. Can I give my dog two NexGard tablets if he weighs more than 50 kg? Yes, for dogs over 50 kg, a combination of tablets is required to achieve the target dose. For example, a 60 kg dog might receive one 136 mg tablet and one 28 mg tablet. You should have your veterinarian calculate the exact combination to ensure safety and efficacy. ### 3. What happens if I give my dog too much NexGard? Overdosing can increase the risk of adverse effects, particularly neurological signs like tremors and seizures. If you suspect an overdose, contact your veterinarian or a pet poison control center immediately. ### 4. What happens if I give my dog too little NexGard? Underdosing may result in incomplete efficacy, allowing fleas and ticks to survive. This can lead to continued infestation and an increased risk of vector-borne disease transmission. Always use the correct weight band. ### 5. Can I give NexGard to my puppy? NexGard is approved for puppies 8 weeks of age and older, weighing at least 2 kg (4.4 lbs). Do not give it to younger or smaller puppies. ### 6. Can I give NexGard to my cat? No. NexGard is specifically formulated and approved for dogs only. Do not administer it to cats, as the safety profile is different. ### 7. Does NexGard treat ear mites? Afoxolaner is not labeled for the treatment of ear mites (*Otodectes cynotis*), though it may have some off-label efficacy. Your veterinarian can recommend an appropriate product for ear mite treatment. ### 8. How quickly does NexGard start working? NexGard begins killing fleas within 4 hours of administration and is highly effective within 24 hours. It provides persistent protection for a full 30 days. ## Sources [1] [Efficacy of a novel oral chewable tablet containing sarolaner, moxidectin and pyrantel (Simparica Trio™) against natural flea and tick infestations on dogs presented as veterinary patients in Europe.](https://pubmed.ncbi.nlm.nih.gov/32113486/) [2] [Comparative efficacy of six monthly doses of Simparica Trio® (sarolaner, moxidectin, and pyrantel chewable tablets) versus NexGard® Plus (afoxolaner, moxidectin, and pyrantel chewable tablets) against a macrocyclic lactone-resistant Dirofilaria immitis isolate in dogs](https://www.semanticscholar.org/paper/9d065d26c86e64617d90fc9057f0b1e90ffed56a) [3] [Efficacy of Afoxolaner (NexGard®) in the treatment of furuncular myiasis caused by Dermatobia hominis fly (Diptera: Cuterebridae) in naturally infested dogs.](https://www.semanticscholar.org/paper/462f3007a186246c6f3b57b0a1511b59f3a2a4f4) [4] [Efficacy of afoxolaner (NexGard®) for the treatment of myiasis caused by the zoonotic tumbu fly, Cordylobia anthropophaga, in domestic dogs under field conditions.](https://www.semanticscholar.org/paper/87fbd933c437bfb5beb070ac7c7465f200accf2d) [5] [Description of a clinical decision support tool with integrated dose calculator for paediatrics](https://www.semanticscholar.org/paper/daa81bc80591f5d14df54d98420378f44a47a884) [6] [Efficacy and safety of afoxolaner (NexGard®) in a collection of captive-bred lizards for the treatment and control of mite infestation](https://www.semanticscholar.org/paper/043f2a3ba29a6693f5ba1d8cb6b038006bc6d2c3) [7] [Efficacy of oral afoxolaner (NexGard®) against natural infestations with Heterodoxus spiniger (Phthiraptera: Boopiidae) in dogs under field conditions.](https://www.semanticscholar.org/paper/b27e729e5cc78d4455d4b36e206d4513bf669091) [8] [Field study to investigate the effectiveness and safety of a novel orally administered combination drug product containing milbemycin oxime and lotilaner (Credelio(®) Plus) against natural flea and tick infestations on dogs presented as veterinary patients in Europe.](https://pubmed.ncbi.nlm.nih.gov/34088338/) [9] [Evaluation of the efficacy of monthly oral administration of afoxolaner plus milbemycin oxime (NexGard Spectra(®), Merial) in the prevention of adult Spirocerca lupi establishment in experimentally infected dogs.](https://pubmed.ncbi.nlm.nih.gov/27514901/) [10] [Weight-based Levothyroxine Dose Calculator for Hypothyroidism in Adults](https://www.semanticscholar.org/paper/8cda053181c5044ea5d5fddec7381b516edeb5e1) [11] [Implementing a Clinician-Built High-Dose Antipsychotic Therapy (HDAT) Calculator and Tracker: A Quality Improvement Project to Optimise HDAT Monitoring and Safe Prescribing](https://www.semanticscholar.org/paper/63456dedd8be8534804ddfa558883d712cfe30e0) [12] [Individualized vancomycin dosing in infants: prospective evaluation of an online dose calculator.](https://www.semanticscholar.org/paper/7542720e8500a0654cfee2349cb1119a4f250f29) [13] [Standardizing Research Methods for Opioid Dose Comparison: The NIH HEAL Initiative Morphine Milligram Equivalent Calculator](https://www.semanticscholar.org/paper/b7078219e6fdc4437bb9a0e887bc2adbbc0dad65) [14] [Controlling intraoperative hyperglycemia in the cardiac surgical patient using the computerized electronic insulin dose calculator](https://www.semanticscholar.org/paper/718a74fc3d880f916a3b4329ffceb4dcf19d3477) [15] [OptimAAPP, a smartphone insulin dose calculator for carbohydrate, fat, and protein: A cross‐over, randomised controlled trial in adolescents and adults with type 1 diabetes using multiple daily injection therapy](https://www.semanticscholar.org/paper/90e867495bd923989cef4f537b6a3e09fa10bafa) [16] [Verification of the utility of the gonadotropin starting dose calculator in progestin‐primed ovarian stimulation: A comparison of empirical and calculated controlled ovarian stimulation](https://www.semanticscholar.org/paper/90725ff968b3a34fa5ba592ced36dff7c066e50e) [17] [NCIRF: an organ dose calculator for patients undergoing radiography and fluoroscopy](https://www.semanticscholar.org/paper/ded16db765f89ae744d0f132f38776fd7e72e803) [18] [The gonadotropins starting dose calculator, which can be adjusted the target number of oocytes and stimulation duration days to achieve individualized controlled ovarian stimulation in Japanese patients](https://www.semanticscholar.org/paper/13548a13740c1eacd3ce3a9e6a80654b0887218b) [19] [P-693 Retrospective evaluation of the effect of the implementation of the DIVINE dose-calculator in daily practice on ovarian hyperstimulation treatment risk and live birth rate](https://www.semanticscholar.org/paper/72455215b9fe6ac1c7b1e11c9117196dc7bbb0cd) [20] [Evaluation of organ and effective doses using anthropomorphic phantom: A comparison between experimental measurement and a commercial dose calculator.](https://www.semanticscholar.org/paper/fd2857d8f01c1f6a972052f5010ee821a63154d6)

## Related Clinical & Scientific Guides * [Drontal Plus Dewormer: Broad-Spectrum Dose Guide by Weight](/knowledge/veterinary-medicine/calculators-clinical-tools/drontal-plus-dewormer-broad-spectrum-dose-guide-by-weight) * [Panacur Fenbendazole Dewormer: Dog Fecal Parasite Treatment Schedule](/knowledge/veterinary-medicine/calculators-clinical-tools/panacur-fenbendazole-dewormer-dog-fecal-parasite-treatment-schedule) * [Prednisolone for Cats: Feline Safe Steroid Dose and Autoimmune](/knowledge/veterinary-medicine/calculators-clinical-tools/prednisolone-for-cats-feline-safe-steroid-dose-and-autoimmune)