Imidocarb

Imidocarb is a carbanilide antiprotozoal used mainly against susceptible Babesia infections and equine piroplasmosis. Veterinary products commonly contain imidocarb dipropionate, with salt identity relevant to formulation strength. Its principal clinical applications are large-Babesia infection in dogs and selected piroplasm infections in horses; response differs substantially among parasite species.

Group

Antiprotozoal

Mechanism of Action

Imidocarb interferes with nucleic-acid metabolism and other essential processes in susceptible protozoa, although its complete mechanism remains unresolved. Inhibition of inositol entry or utilization in infected erythrocytes has been proposed to disrupt parasite survival and replication. These effects contribute to suppression or elimination of susceptible blood-stage organisms, with the outcome depending on the parasite species and regimen.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Babesiosis	6.6 mg/kg	IM, SC	Every 336 h	Up to 14 days; Dipropionate formulation. Two treatments only, 14 days apart.
Historical ehrlichiosis regimen	Reference only	IM		6.6 mg/kg, repeated once after 14 days. This historical reported guidance use is distinct from the labelled babesiosis indication; efficacy and salt basis require assessment.
Babesiosis	5–6.6 mg/kg	IM, SC	Every 336 h	Up to 14 days; Two treatments 14 days apart; distinct lower-range alternative to the labelled 6.6 mg/kg dose.
Babesiosis single treatment	7.5 mg/kg	IM, SC	Once
Hepatozoon canis infection	5 mg/kg	IM, SC	Every 336 h	Usually 1-2 treatments, continued until parasitaemia clears.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Historical tick-borne infection regimen	5 mg/kg	IM	Every 336 h	Up to 14 days; Imidocarb dipropionate; two treatments 14 days apart. Select an indication-specific regimen when the diagnosis is known.
Feline haemoplasmosis	5 mg/kg	IM, SC	Every 336 h	Alternative when doxycycline is not tolerated; continue until PCV is maintained.
Cytauxzoon felis infection	3–4 mg/kg	IM	Every 168 h	Two treatments 7 days apart; efficacy not proven. Requires intensive supportive care and consideration of anticholinergic pretreatment.
Cytauxzoon felis infection	5 mg/kg	IM	Every 336 h	Up to 14 days; Two treatments; efficacy remains uncertain.
Ehrlichial or anaplasma infection	5 mg/kg	IM	Every 336 h	Alternative to doxycycline; at least 2-4 treatments.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Piroplasmosis	Reference only	IM		Reported alternatives include 4.4 mg/kg once or 2.2 mg/kg at 24-48-hour intervals; the treatment-count wording for the latter is corrupted and must not be guessed. Salt basis is not explicit.
Babesia caballi clearance	Reference only	IM		4 mg/kg for four treatments 72 hours apart; salt basis is not explicit in the combined-salt monograph.
Piroplasmosis clinical treatment	2.2 mg/kg	IM	Once	Imidocarb dipropionate; suppression of clinical signs does not establish organism clearance.
Babesia caballi clearance	2 mg/kg	IM	Every 24 h	Up to 1 days; Two consecutive daily treatments.
Theileria equi clearance	4 mg/kg	IM	Every 72 h	Four treatments at 72-hour intervals; keep treatment count explicit.

Sheep

Use / stage	Dose	Route	Schedule	Instructions
Babesiosis	1.2 mg/kg	IM	Every 240–336 h	Initial treatment plus one repeat 10-14 days later.

Indications

Treatment of canine babesiosis caused by susceptible large Babesia species, including Babesia canis.
Treatment of equine piroplasmosis caused by Babesia caballi or Theileria equi within a parasite-specific protocol.
Treatment of selected canine Hepatozoon canis infections, often within a combination regimen.
Treatment of selected susceptible babesiosis in other domestic or exotic species where a supported regimen is available.

Contraindications

Intravenous administration
Avoid in donkeys and mules because of increased susceptibility.
Assess risk in pulmonary, renal or hepatic impairment.

Interactions

Cholinesterase-inhibiting drugs and pesticides can increase cholinergic toxicity.

Adverse effects

Injection pain, vomiting and transient liver enzyme increases
Salivation, bronchoconstriction, diarrhoea, sweating and colic
High-dose renal tubular and hepatic injury

Toxicity

Stop exposure and support respiration and circulation. Severe cholinergic signs may require atropine.

Preparations

Preparation	Form	Strength	Route
Imizol imidocarb dipropionate 120 mg/mL injection Do not administer IV. Labelled canine dose is based on imidocarb dipropionate.	Injection	120 mg / mL	IM, SC

Monitoring and Administration

Rotate injection sites. Hydrochloride is more irritating than dipropionate.

In horses, pretreatment described for cholinergic effects includes atropine 0.02 mg/kg IV or glycopyrrolate 0.0025 mg/kg IV; an antispasmodic alternative is also described.

Protect from light at room temperature. Safety in puppies and breeding, pregnant or lactating dogs is not established.

For severe canine ehrlichiosis, a historical combined course uses imidocarb 5 mg/kg SC once or twice 15 days apart with doxycycline 10 mg/kg/day for 28 days. Imidocarb alone did not clear experimental E. canis infection. A canine babesiosis combination gives imidocarb 6 mg/kg the day after diminazene 3.5 mg/kg; it is not an imidocarb-only regimen.