Milbemycin oxyme is a macrocyclic lactone with a broad spectrum of activity that is used exclusively in dogs and cats, so far only for oral administration (tablets, chewables, etc).

It is effective against heartworms and numerous other roundworms and also against some mite species. However, it is ineffective against tapeworms and flukes and other external parasites. So far it is not used in livestock or horses, nor in crop protection.

However, resistance of heartworm microfilariae to ivermectin has been reported in the USA (particularly in the South), with cross-resistance to macrocyclic lactones, including milbemycin oxime.

The table below indicates some usual dosing recommendations for milbemycin oxime issued by manufacturers or documented in the scientific literature. They may not be approved in some countries.

Dosing recommendations for MILBEMYCIN OXIME
Warning!: Tolerance and safety margin in dogs with the MDR-1 mutation (e.g. Collies) sensitive to ivermectin are higher for milbemycin oxime than for ivermectin. Consequently the recommended dose can be admnistered to dogs with de MDR-1 mutation, however puppies are more sensitive. In sensitive dogs the recommended dose of 0.5 mg/kg should not be exceeded bacause the therapeutic margin is lower than in the non-sensite dogs.
Delivery Parasites Dose (against milbemycin-susceptible parasites)
Oral Toxocara canis, pupppies
0.5 mg/kg; first treatment at 2 weeks age, rep every 4 weeks until week 26
Oral Ancylostoma caninum 0.5 mg/kg, rep after 30 days if needed
Oral Dirofilaria immitis prevention 0.25 mg/kg monthly
Oral Dirofilaria immitis ≤2 months larvae
0.5 mg/kg, rep after 30 days if needed
Oral Dirofilaria immitis 3 months larvae
0.5 mg/kg monthly for 13 months
Oral Dirofilaria immitis 4 months larvae
0.5 mg/kg monthly for 14 months controls only ~50% of the parasites
Oral Trichuris vulpis 0.5 mg/kg
Oral Pneumonyssoides caninum 1 mg/kg, 3x with 10 days interval; or 0.5-1 mg/kg weekly for 3 weeks
Oral Sarcoptes scabiei 0.75 mg/kg/day for 30 days; or 2 mg/kg, 3x with 10 days interval
Oral Generalized demodicosis 1-2 mg/kg/day until 30 days following a negative skin scrapping (aver. duration 60-180 days); or 0.5-1 mg/kg 2×/day, until 30 days following a negative skin scrapping (aver. duration 90 days)
Delivery Parasite Dose (against milbemycin-susceptible parasites)
Oral Ancylostoma tubaeforme 2-4 mg/kg; at 2 mg/kg efficacy may be <90%
Oral  Toxocara cati 2-4 mg/kg; at 2 mg/kg efficacy may be <90%
Oral Dirofilaria immitis prevention 2-4 mg/kg monthly

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Dosing recommendations for antiparasitics depend on national regulations. National regulatory authorities determine whether a product is approved for a given indication, i.e. use on a particular host at a specific dose and against a specific parasite. Check the labels of the products available in your country for specific information on approved indications.

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