Milbemycin
Milbemycin oxime is used for heartworm prevention, intestinal nematodes and selected mite infections; high-dose mange protocols have greater toxicity risks.
Group
Macrocyclic lactone antiparasitic
Mechanism of Action
Potentiates parasite glutamate-gated chloride channels, causing paralysis and death. Mammalian toxicity can occur when central nervous system exposure increases.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Heartworm and intestinal nematode prevention | 0.5 mg/kg | PO | Every 720 h | Every 30 days. |
| Demodicosis | 2 mg/kg | PO | Every 24 h | Up to 120 days; Do not use in: Macrocyclic-lactone sensitivity; Reported course 60-120 days; high-dose therapy requires tolerance and parasitological monitoring. |
| Demodicosis staged treatment — Initial | 1 mg/kg | PO | Every 24 h | Do not use in: Macrocyclic-lactone sensitivity; Continue until clinical cure before switching to the weekly stage. |
| Demodicosis staged treatment — Maintenance | 3 mg/kg | PO | Every 168 h | Do not use in: Macrocyclic-lactone sensitivity; After clinical cure; continue until parasitological cure with negative scrapings. |
| Sarcoptic mange | 2 mg/kg | PO | Every 168 h | Up to 35 days; Course 3-5 weeks. |
| Cheyletiellosis | 2 mg/kg | PO | Every 168 h | |
| Heartworm and intestinal nematode prevention | 0.5–0.99 mg/kg | PO | Every 720 h | Product-specific minimum age/weight and tablet selection apply. |
| Microfilariae after adulticide | 0.5 mg/kg | PO | About one month after melarsomine; a two-week repeat may be used before resuming monthly prevention. | |
| Sarcoptic mange | 0.75 mg/kg | PO | Every 24 h | Up to 30 days; Separate daily alternative. |
| Nasal-mite-associated rhinitis | 1 mg/kg | PO | Every 240 h | Three treatments at 10-day intervals. |
| Escalating Demodex treatment | Reference only | PO | Start 1 mg/kg/day; after 30 days with minimal improvement increase to 2 mg/kg/day, and after another 30 days consider 3 mg/kg/day or an alternative. ABCB1-mutant dogs can show toxicity at 1-2.2 mg/kg/day; maintain skin-scraping and neurologic monitoring. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Heartworm and intestinal nematode prevention | 2 mg/kg | PO | Every 720 h | Every 30 days. |
| Demodicosis | 1–2 mg/kg | PO | Every 24 h |
Reptiles
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Nematodes | Reference only | PO | 0.5-1 mg/kg, repeated after 2 weeks; fecal examination 14 days after the second treatment guides further doses. Chelonian tolerance is described, unlike ivermectin, but species assessment remains necessary. |
Indications
- Susceptible nematode and ectoparasite infections
- Heartworm prevention with specific small-animal products
Contraindications
- High-dose use in ABCB1-sensitive animals requires particular caution.
- Previous sensitivity to macrocyclic lactones
Interactions
- P-glycoprotein inhibitors, including azole antifungals and cyclosporine, can increase central nervous system exposure.
Adverse effects
- Hypersalivation, ataxia, visual disturbance and central depression
- Severe overdose may cause coma or death
Toxicity
Stop exposure and provide respiratory and neurologic support. Prevent further absorption when appropriate; lipid-emulsion treatment may be considered in severe lipophilic-drug intoxication.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Milbemycin oxime 2.3 mg tablet | Tablet | 2.3 mg / tablet | PO |
| Milbemycin oxime 5.75 mg tablet | Tablet | 5.75 mg / tablet | PO |
| Milbemycin oxime 11.5 mg tablet | Tablet | 11.5 mg / tablet | PO |
| Milbemycin oxime 23 mg tablet | Tablet | 23 mg / tablet | PO |
Monitoring and Administration
Establish heartworm status before preventive treatment and use fecal examinations or skin scrapings to assess other parasite responses.
Protect from light. Do not substitute concentrated livestock products for small-animal products without exact concentration and formulation assessment.
Isoxazolines are generally preferred over prolonged high-dose milbemycin for canine demodicosis.
High-dose demodicosis treatment may require months; assess skin scrapings rather than relying on clinical appearance alone.
The cited Interceptor label excludes puppies under 4 weeks or 2 lb and kittens under 6 weeks or 1.5 lb. These are presentation-specific historical minimums rather than universal limits for every milbemycin combination. Susceptible dogs should undergo ABCB1 assessment before high-dose treatment.