Amitraz

Amitraz is a formamidine ectoparasiticide with activity against susceptible mites and ticks. A principal veterinary use is topical treatment of canine demodicosis by dip or sponge-on application. Its clinical role has declined with availability of other effective acaricides, including oral isoxazolines.

Amitraz is a parasite neuroactive drug used in species- and formulation-specific topical products. Its mammalian pharmacology includes adrenergic activity, which is distinct from its effects on parasite neurotransmission.

Group

Topical acaricide

Mechanism of Action

Amitraz and active metabolites act at arthropod octopamine receptors and can inhibit monoamine oxidase. Octopamine is important in parasite neural and muscular signaling; disruption of this signaling interferes with movement, feeding and other functions needed for survival. These actions produce acaricidal activity against susceptible mites and ticks.

In mammals, an important action is alpha-2 adrenergic receptor stimulation. Reduced norepinephrine release and altered central autonomic signaling can produce sedation, bradycardia, hypothermia and changes in gastrointestinal function. Suppression of insulin release contributes to hyperglycemia after significant exposure.

Selective acaricidal activity reflects differences between arthropod amine-signaling pathways and mammalian receptor responses. Mammalian alpha-2 receptor activation remains possible after absorption, and systemic effects increase with exposure.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Demodectic mange	Reference only	TOPICAL	Every 336 h	Dilute 10.6 mL of the 19.9% concentrate in 7.5 L water to approximately 0.025%; apply 3–6 treatments. Concentration-based dipping is not a body-weight dose.
Refractory demodectic mange	Reference only	TOPICAL		Reported concentrations are 0.025%, 0.05% or 0.1%, applied once or twice weekly. Extreme refractory courses used 0.125% on half the body one day and the other half the next, alternating daily for 4 weeks to 5 months; adverse effects increase with concentration.

Indications

Topical treatment of canine demodicosis caused by Demodex mites.
Management of generalized canine demodicosis as part of a plan addressing concurrent skin disease.
Control of susceptible ticks and other mites in species- and formulation-specific applications.

Contraindications

Do not administer systemically.
Higher topical concentrations carry greater adverse-effect risk.

Interactions

Do not combine with monoamine oxidase inhibitors such as selegiline.
Do not combine with other alpha2 agonists.

Adverse effects

Sedation, pruritus, polyuria and polydipsia.
Bradycardia, hypotension, heart block, hypothermia and hyperglycemia.
Seizures are uncommon.

Toxicity

Alpha2-related effects may be reversed with yohimbine or atipamezole.

Preparations

Preparation	Form	Strength	Route
Amitraz 19.9% dip concentrate 10.6 mL concentrate presentation; dilute before use.	Other	199 mg / mL	TOPICAL

Monitoring and Administration

Assess response with serial skin scrapings. Start with the standard dilution rather than refractory-case concentrations.

Store concentrate tightly sealed, protected from light, at room temperature.