Fenbendazole dosage for a medium breed
22–77 lb (10–35 kg)
The short answer
For a dog weighing 22–77 lb (10–35 kg), the dose of Fenbendazole reported in the literature is 50 mg/kg per day (three days on, four days off), given 3 consecutive days weekly, over 4-12+ weeks. It is studied in this weight class primarily for investigational oncology adjunct. These figures are reported as published and are not recommendations — the dose for an individual dog must be set by a veterinarian who has examined the animal.
Worked examples at specific weights
Calculated from the reported range of 50–50 mg per kg of body weight.
| Body weight | Calculated dose range | Frequency |
|---|---|---|
| 15 kg (33 lb) | 750 mg | 3 consecutive days weekly |
| 23 kg (51 lb) | 1150 mg | 3 consecutive days weekly |
| 30 kg (66 lb) | 1500 mg | 3 consecutive days weekly |
For an exact figure at your dog's weight, use the dose calculator.
Typical breeds in this weight class
Beagle, Border Collie, Australian Shepherd, Bulldog, Cocker Spaniel and similarly sized dogs generally fall within 22–77 lb (10–35 kg). Weigh your dog rather than estimating — dosing is calculated per kilogram and an estimate that is out by a few kilos changes the figure materially, particularly at the smaller end.
Before dosing at all
⚠ Bone marrow suppression with extended dosing
Pancytopenia and bone marrow hypoplasia are documented in dogs given fenbendazole — in published case reports rather than a systematic series. A Doberman developed pancytopenia twelve days into treatment and recovered within about two weeks of stopping the drug, and a 2025 case reported the same picture with febantel, which the body metabolises to fenbendazole. Both dogs recovered on discontinuation. The reaction appears uncommon but is real, and it is the reason protocols use three-on / four-off cycling with regular CBC monitoring. Pale gums, lethargy, or appetite loss warrant immediate veterinary attention.
⚠ Do not combine with vincristine or paclitaxel
Both agents act on the same microtubule apparatus as fenbendazole — vincristine by destabilising it, paclitaxel by stabilising it. The target is shared either way, and concurrent use risks additive toxicity. Any dog on conventional chemotherapy needs its oncologist involved before fenbendazole is added.
Common questions
How much Fenbendazole for a medium breed?+
For a dog in the 22–77 lb (10–35 kg) range, the reported dose is 50 mg/kg per day (three days on, four days off), given 3 consecutive days weekly, typically for 4-12+ weeks. At a representative weight of 23 kg (about 51 lb), that works out to roughly 1150 mg per dose. These figures are reported from the source literature and are not recommendations.
How often should a medium breed be given Fenbendazole?+
3 consecutive days weekly is the reported frequency, over a course of 4-12+ weeks. See the cycling guide for how breaks are structured.
Is Fenbendazole safe for a medium breed?+
Fenbendazole at its labelled three-day deworming dose is one of the safest drugs in veterinary medicine, which is exactly why the extended oncology schedules get discussed so casually — and why that framing is misleading. Published canine case reports document pancytopenia and bone marrow hypoplasia during fenbendazole therapy, both resolving after the drug was withdrawn, and hepatic injury has been reported in humans self-administering it. Those reports are individual cases rather than a controlled series, so the true frequency is unknown — which is an argument for the monitoring, not against it. The three-on / four-off cycling and the monthly CBC exist specifically to manage that risk. It also must not be combined with vincristine or paclitaxel.
References
- 1.Dogra N, Kumar A, Mukhopadhyay T Fenbendazole acts as a moderate microtubule destabilizing agent and causes cancer cell death by modulating multiple cellular pathways. Scientific Reports, 2018. PMID 30093705
- 2.Duan Q, Liu Y, Rockwell S Fenbendazole as a potential anticancer drug. Anticancer Research, 2013. PMID 23393324
- 3.Nguyen J, Chong CR Oral Fenbendazole for Cancer Therapy in Humans and Animals. Anticancer Research, 2024. PMID 39197912
- 4.Jung H, Lee J, Kim Y, et al. Fenbendazole Exhibits Differential Anticancer Effects In Vitro and In Vivo in Models of Mouse Lymphoma. Current Issues in Molecular Biology, 2023. PMID 37998737
- 5.Pan T, et al. Fenbendazole induces pyroptosis in breast cancer cells through HK2/caspase-3/GSDME signaling. Frontiers in Pharmacology, 2025. PMID 40756987
- 6.CANINE STUDYGary AT, Kerl ME, Wiedmeyer CE, et al. Bone marrow hypoplasia associated with fenbendazole administration in a dog. Journal of the American Animal Hospital Association, 2004. PMID 15131104
- 7.CANINE STUDYPetronzio A, Carabetta D, Koid A Bone marrow toxicity associated with febantel administration in a dog: Case Report. Frontiers in Veterinary Science, 2025. PMID 40260210
Other weight classes: Fenbendazole for a small / toy breed, Fenbendazole for a large / giant breed.
Educational information — not veterinary medical advice
Everything on this page is compiled from published peer-reviewed literature for educational and research purposes. It does not establish a veterinarian-client-patient relationship (VCPR) and is not a substitute for veterinary examination and diagnosis. Most compounds described here are investigational or used off-label and are not FDA-approved for these purposes in dogs. Extralabel drug use in animals requires a valid VCPR and the direct supervision of a licensed veterinarian under AMDUCA (21 U.S.C. §360b). Dosing figures are reported as they appear in the source literature and are not recommendations.