Selamectin
Selamectin is a topically administered macrocyclic lactone used mainly in dogs and cats. Its clinical spectrum includes heartworm prevention, fleas and selected mites, with intestinal nematode coverage in cats. Additional extra-label ectoparasite uses have been reported in companion and exotic animals. Combination products may broaden the spectrum through other active ingredients.
Group
Macrocyclic lactone antiparasitic
Mechanism of Action
Selamectin activates parasite glutamate-gated chloride channels, increasing chloride permeability and hyperpolarizing susceptible nerve and muscle cells. Impaired excitability disrupts movement and feeding and leads to paralysis and death. Activity against developing Dirofilaria immitis larvae supports heartworm prevention. Systemic and tissue exposure after topical administration contributes to its effects on susceptible ectoparasites and nematodes.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Heartworm prevention | 6–12 mg/kg | TOPICAL | Every 720 h | Do not use in: Dogs younger than 6 weeks; Every 30 days; preferred feline amount is 6 mg/kg. |
| Flea and ear-mite control | 6–12 mg/kg | TOPICAL | Every 720 h | Do not use in: Dogs younger than 6 weeks; Every 30 days; preferred feline amount is 6 mg/kg. |
| Sarcoptic mange | 6–12 mg/kg | TOPICAL | Every 720 h | Do not use in: Dogs younger than 6 weeks; Two applications 30 days apart. |
| Sarcoptic mange | 6–12 mg/kg | TOPICAL | Every 336–504 h | Do not use in: Dogs younger than 6 weeks; Alternative 2-3 week dermatology schedule. |
| Nasal mites | 6–24 mg/kg | TOPICAL | Every 336 h | Three treatments at 2-week intervals. |
| Cheyletiellosis | 6–12 mg/kg | TOPICAL | Every 336 h | Four treatments. |
| Biting lice | 6 mg/kg | TOPICAL | Once |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Heartworm prevention | 6–12 mg/kg | TOPICAL | Every 720 h | Do not use in: Cats younger than 8 weeks; Every 30 days; preferred feline amount is 6 mg/kg. |
| Flea and ear-mite control | 6–12 mg/kg | TOPICAL | Every 720 h | Do not use in: Cats younger than 8 weeks; Every 30 days; preferred feline amount is 6 mg/kg. |
| Flea and ear-mite control | 6 mg/kg | TOPICAL | Every 720 h | Do not use in: Cats younger than 8 weeks; Preferred feline amount. |
| Sarcoptic mange | 6–12 mg/kg | TOPICAL | Every 720 h | Do not use in: Cats younger than 8 weeks; Two applications 30 days apart. |
| Sarcoptic mange | 6–12 mg/kg | TOPICAL | Every 336–504 h | Do not use in: Cats younger than 8 weeks; Alternative 2-3 week dermatology schedule. |
| Biting lice | 6 mg/kg | TOPICAL | Once | |
| Notoedric mange | 6 mg/kg | TOPICAL | Once | |
| Hookworms or roundworms | 6 mg/kg | TOPICAL | Once |
Ferrets
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Heartworm prevention | 18 mg/kg | TOPICAL | Every 720 h |
Rabbits
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Ear mites | 6–18 mg/kg | TOPICAL | Repeat interval unspecified. |
Indications
- Prevention of heartworm disease in dogs and cats with an indicated product.
- Treatment and control of flea infestations and ear mites in dogs and cats.
- Treatment of sarcoptic mange and selected tick infestations in dogs where included in the product indication.
- Treatment and control of susceptible roundworms and hookworms in cats.
- Extra-label treatment of selected notoedric mange, cheyletiellosis, biting lice or canine nasal-mite infestations with a species-appropriate regimen.
Contraindications
- Dogs younger than 6 weeks
- Cats younger than 8 weeks
Adverse effects
- Local alopecia/inflammation, salivation, lethargy, nausea, tachypnea or tremor.
Toxicity
Accidental oral exposure can cause salivation, vomiting, lethargy or ataxia. Avermectin-sensitive patients can be more vulnerable to neurologic effects.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Selamectin spot-on 60 mg/mL | Other | 60 mg / mL | TOPICAL |
| Selamectin spot-on 120 mg/mL | Other | 120 mg / mL | TOPICAL |
Monitoring and Administration
Apply to skin and assess heartworm status. Use the appropriate species formulation and avoid ingestion.
In heavy canine tick infestation, a repeat 2 weeks after the first application is described. Ear-mite or sarcoptic treatment may be repeated at one month if necessary; prevention and one-time treatment schedules are not interchangeable.
Selamectin spot-on liquid is flammable; keep below 30 C away from ignition.