Oxfendazole
Oxfendazole is a **benzimidazole anthelmintic** primarily indicated for use in cattle to remove and control lungworms, roundworms (including inhibited forms of *Ostertagia ostertagi*), and tapeworms. - **Broad-spectrum activity**: Effective against a variety of pathogenic internal parasites. - **Extra-label use**: Frequently utilized in horses, sheep, goats, swine, and dogs. - **Clinical Pearl**: Oxfendazole is the active sulfoxide metabolite of fenbendazole. It offers improved gastrointestinal absorption compared to many other benzimidazoles, leading to higher plasma concentrations and longer resident times.
Mechanism: Oxfendazole exerts its antiparasitic effects by disrupting intracellular microtubular transport systems within the parasite. - Binds selectively to and damages **tubulin** → prevents tubulin polymerization → inhibits **microtubule** formation. - At higher concentrations, it disrupts metabolic pathways and inhibits key metabolic enzymes, including **malate dehydrogenase** and **fumarate reductase**, ultimately depleting the helminth's energy reserves and causing death.
Dosing by species
- For susceptible parasites · 5 mg/kg PO · PO · Single dose
- For susceptible parasites · 7.5 mg/kg PO · PO · Single dose
- For susceptible parasites · 4.5 mg/kg either PO or via intraruminal injection (22.5% only). May repeat in 4-6 weeks. Dose of the 9.06% suspension is 2.5 mL per 100 lb (50 kg) of body weight PO. Dose of the 22.5% suspension is 1 mL per 100 lb (50 kg) of body weight either PO or intraruminal injection. · PO/intraruminal · Single dose, may repeat in 4-6 weeks · See package label for specific directions if giving by intraruminal injection.
- For susceptible parasites · 10 mg/kg PO · PO · Single dose
- For susceptible parasites · 3-4.5 mg/kg PO · PO · Single dose
- For Oslerus osleri · 10 mg/kg PO once daily for 28 days. · PO · q24h · 28 days
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Female dairy cattle of breeding age
Adverse effects
- Hypersensitivity reactions (theoretically possible secondary to antigen release by dying parasites, particularly at high dosages)
Drug interactions
- Bromsalan flukicides (dibromsalan, tribromsalan) · Concurrent use is contraindicated; abortions in cattle and death in sheep have been reported after using these compounds together.
Monitoring
- Clinical efficacy (resolution of clinical signs, fecal egg counts)
Overdose
> **Safety Profile**: Oxfendazole has a wide margin of safety. Doses of 10 times those recommended elicited no adverse reactions in horses tested. It is highly unlikely that this compound would cause serious acute toxicity when given alone.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.