Milbemycin oxime: veterinary dose and monograph

At a glance

Drug class

Antiparasitic

Also known as

Interceptor, Milbemax

Species with doses

Dogs, Cats and Reptiles

General dose range

0.5–2 mg/kg PO monthly (prevention) — check the species tables for the indication

Routes

PO

Last reviewed

1 October 2026

Indications

• Heartworm prevention
• Intestinal nematodes (Toxocara, Ancylostoma, Trichuris)
• Generalised demodicosis (high daily dose, off-label)

Milbemycin oxime dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Heartworm / intestinal worm prevention: Papich 5e and Plumb’s p.840 (Interceptor label): minimum 0.5 mg/kg PO once monthly (label bands 0.5–0.99 mg/kg) for heartworm prophylaxis, hookworms, roundworms and whipworms, from 4 weeks of age and 2 lb. Microfilaricide after adulticide: the preventive dose, repeated in 2 weeks if needed.
• Generalised demodicosis: Papich 5e: 2 mg/kg q24h PO for 60–120 days, or 1 mg/kg/day until clinical cure then 3 mg/kg weekly until negative scrapings. Plumb’s p.840 (Merchant 2009): start 1 mg/kg/day, scrape at 30 days, increase to 2 mg/kg then 3 mg/kg/day if needed. Check for microfilariae first. ABCB1 (MDR1) mutant dogs can show neurotoxicity at 1–2.2 mg/kg/day.
• Sarcoptic mange / cheyletiellosis: Papich 5e: sarcoptic mange 2 mg/kg q7 days for 3–5 weeks; cheyletiellosis 2 mg/kg weekly. Plumb’s p.840 (White 2000): 2 mg/kg PO every 7 days for 3 doses, or scabies 0.75 mg/kg once daily for 30 days. Nasal mites: 1 mg/kg every 10 days for 3 treatments.

Cats

• Heartworm / worm prevention: Papich 5e and Plumb’s p.840 (Interceptor for Cats label): 2 mg/kg PO once monthly for heartworm prevention, hookworms and roundworms.
• Demodicosis: Papich 5e: cats with demodicosis 1–2 mg/kg q24h PO.

Reptiles

• Nematodes (incl. chelonians): Plumb’s p.840 (de la Navarre 2003): 0.5–1 mg/kg PO, repeated in 2 weeks and again if the faecal is still positive 14 days after the second dose. Appears safe in chelonians, unlike ivermectin.

Contraindications

Test for heartworm before starting in endemic regions (microfilaricidal — rapid kill can cause a reaction in heavily microfilaraemic dogs). Caution with high demodex doses in MDR1-mutant breeds.

Species-specific warnings

Dogs: High demodicosis doses can cause avermectin neurotoxicity in MDR1/ABCB1-mutant collies, Australian shepherds and related breeds — test or titrate cautiously.

Adverse effects

• Usually very well tolerated at preventive dose
• Transient lethargy / GI upset
• Microfilarial-kill reaction in heavily positive dogs

Drug interactions

• Avoid concurrent high-dose macrocyclic lactones in MDR1-mutant dogs
• Formulated with praziquantel (Milbemax) and other actives in combination products
• No major metabolic interactions at the preventive dose

Pregnancy and lactation

Considered safe at preventive doses in breeding, pregnant and lactating dogs; the high off-label demodicosis dose is less characterised — use clinical judgement.

Monitoring

• Heartworm antigen / microfilaria test before the first dose in endemic areas
• Skin scrapes to a negative endpoint when used for demodicosis
• Neurological signs in MDR1 breeds on high daily doses

Toxicity and overdose

Preventive doses have a wide margin. In heavily microfilaraemic dogs a rapid microfilarial kill can trigger a shock-like reaction. High doses in ABCB1/MDR1-mutant herding breeds can cause avermectin-type neurotoxicity (ataxia, tremor, coma).

Clinical pearls

• Always confirm heartworm-negative before the first dose in endemic areas to avoid a microfilarial reaction
• The same molecule jumps from monthly prevention to daily demodex therapy — very different dose and duration
• Milbemax adds praziquantel when tapeworm cover is also needed

Mechanism of action

Milbemycin (macrocyclic lactone). Activates parasite glutamate-gated chloride channels → paralysis and death of nematode larvae and adults and of microfilariae. Kills migrating L3/L4 Dirofilaria larvae for heartworm prevention and clears adult intestinal nematodes.

Formulations and products

• Interceptor 2.3–23 mg tablet (by bodyweight band)
• Milbemax (milbemycin + praziquantel) tablet
• Interceptor (Elanco) — 2.3 / 5.75 / 11.5 / 23 mg, Flavour tablet
• Milbemax (Elanco) — Milbemycin oxime + praziquantel, Film-coated tablet

Storage

Store at room temperature, dry.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other antiparasitics

• Lufenuron
• Mebendazole
• Meglumine Antimoniate
• Melarsomine
• Monensin
• Monepantel
• Morantel
• Moxidectin

Frequently asked questions