Vetdrugs 2.0Afoxolaner is an orally administered isoxazoline ectoparasiticide used in dogs to kill susceptible fleas, ticks and mites. Systemic exposure allows parasites to encounter the drug while feeding on the treated animal. It is used for continuing flea and tick control and in supported treatment regimens for canine demodicosis and sarcoptic mange.
Afoxolaner is a systemic parasite neurotoxicant with flea, tick and mite activity. The spectrum and duration of protection vary with the parasite and product. Combination preparations contain additional active ingredients with their own pharmacologic actions.
Group
Isoxazoline ectoparasiticide
Mechanism of Action
Afoxolaner inhibits arthropod ligand-gated chloride channels, particularly channels activated by gamma-aminobutyric acid (GABA). These channels normally allow inhibitory chloride currents that restrain neural activity. Blocking them disrupts inhibitory neurotransmission and causes uncontrolled excitation, paralysis and death of susceptible insects and acarines.
After oral absorption, afoxolaner is available systemically, and feeding parasites are exposed through the host. This explains why it can control ectoparasites without being applied directly to each parasite and why killing after exposure is different from preventing attachment or biting.
Arthropod channels are more sensitive than mammalian channels, providing selective toxicity. That selectivity does not mean mammalian neurologic effects are impossible: isoxazoline-associated tremors, ataxia and seizures have been reported in dogs. Parasite death also does not guarantee that every vector-borne infection will be prevented.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Flea and tick control | 2.7–7 mg/kg | PO | Alternative established weight-band exposure range. Give whole chews monthly using the corresponding product weight table; do not divide tablets. | |
| Demodicosis | 2.7–7 mg/kg | PO | Whole weight-band chews monthly until two negative skin scrapings one month apart; address underlying disease. Do not use a twice-weekly schedule. | |
| Sarcoptic mange | 2.7–7 mg/kg | PO | Whole weight-band chews monthly for two consecutive months, followed by clinical and skin-scraping reassessment. | |
| Flea and tick control | 2.5 mg/kg | PO | Distinct minimum-exposure description for a monthly product label, not an exact dose to be divided from any chew. It does not replace the saved 2.7–7 mg/kg whole-product weight-band presentations. The supplied text also describes twice-weekly use for Demodex without a separate complete product-specific protocol; do not infer a new weight-band schedule. |
Indications
- Treatment and prevention of adult flea infestations in dogs, including Ctenocephalides felis, to reduce flea burden and subsequent environmental contamination.
- Treatment and control of susceptible tick infestations in dogs, with coverage dependent on the tick species and product.
- Treatment of canine demodicosis caused by Demodex mites.
- Treatment of canine sarcoptic mange using supported regimens.
- Flea elimination as part of the management of flea-associated dermatitis in dogs.
Contraindications
- Use cautiously in dogs with seizures or other neurologic disorders.
- Safety in pregnant, lactating or breeding dogs is not established for the single-ingredient chews described here.
- Do not extrapolate these canine regimens to cats or food-producing animals.
- Young or very small puppies require product-specific eligibility assessment; the 2.5 mg/kg minimum-dose label applies from 8 weeks and 4 lb body weight.
Interactions
- No clinically important interactions were identified with common concomitant treatments in the cited product field studies.
Adverse effects
- Vomiting, diarrhea, anorexia, lethargy or pruritus.
- Tremors, ataxia or seizures, including in dogs without a prior neurologic history.
Toxicity
Overexposure can be associated with gastrointestinal or neurologic signs. There is no specific antidote described; manage clinical signs and review the amount consumed, particularly after accidental access to multiple chews.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| NexGard 11.3 mg Chewables Single-ingredient afoxolaner chew. Select whole chews using this presentation's weight-band table; combination NexGard products are different formulations. Whole tablets only; dog 2–4 kg: 1 tablet. | Tablet | 11.3 mg / tablet | PO |
| NexGard 28.3 mg Chewables Single-ingredient afoxolaner chew. Select whole chews using this presentation's weight-band table; combination NexGard products are different formulations. Whole tablets only; dog >4–10 kg: 1 tablet. | Tablet | 28.3 mg / tablet | PO |
| NexGard 68 mg Chewables Single-ingredient afoxolaner chew. Select whole chews using this presentation's weight-band table; combination NexGard products are different formulations. Whole tablets only; dog >10–25 kg: 1 tablet. | Tablet | 68 mg / tablet | PO |
| NexGard 136 mg Chewables Single-ingredient afoxolaner chew. Select whole chews using this presentation's weight-band table; combination NexGard products are different formulations. Whole tablets only; dog >25–50 kg: 1 tablet. | Tablet | 136 mg / tablet | PO |
Monitoring and Administration
Monthly treatment is used for flea and tick control and for selected mite infestations.
Some single-ingredient chew labels specify a minimum exposure of 2.5 mg/kg; others use a 2.7-7 mg/kg weight-band range. Select whole chews with the table for the exact presentation rather than treating a minimum as an exact dose.
Keep chewables in their original manufacturer packaging, protected from light at room temperature.
Administer the whole chew for the exact product weight band and confirm it is consumed. Do not use information for a different strength or combination product to reconstruct a dose for the single-active preparation.