Imidocarb
**Imidocarb dipropionate** is a diamidine antiprotozoal agent primarily used in veterinary medicine to treat tick-borne protozoal infections. **Key Clinical Applications:** - **Babesiosis**: Highly effective against *Babesia canis* in dogs, as well as *Babesia* species in horses and sheep. - **Cytauxzoonosis**: Used in cats for *Cytauxzoon felis* infections, often as part of a comprehensive treatment protocol. - **Other Uses**: Sometimes utilized as an alternative or adjunct treatment for *Ehrlichia canis*, *Hepatozoon canis*, and feline hemotropic mycoplasmas (e.g., *Mycoplasma haemofelis*). *Clinical Pearl*: While highly effective for *B. canis*, it is generally less effective against *B. gibsoni*. It does not clear the encysted stage of *Hepatozoon americanum*.
Mechanism: Imidocarb acts by directly targeting the **nucleic acids** of susceptible protozoal organisms. - It binds to and intercalates with **DNA** โ causing the double helix to unwind and denature. - This structural damage โ **inhibits cellular repair and replication** โ leading to parasite death. - *Mechanistic Note*: As a diamidine derivative, it may also interfere with polyamine synthesis and function, further disrupting the parasite's metabolic pathways.
Dosing by species
- Cytauxzoon felis ยท 3-4 mg/kg ยท IM ยท repeated 7 days after initial dose ยท Efficacy not proven. Cholinergic effects can be mitigated by pre-treating with atropine. Must also give supportive therapy (IV fluids, prophylactic heparin, nutritional/nursing care, analgesia, and potentially transfusion).
- Cytauxzoon felis ยท 5 mg/kg ยท IM ยท once and then 14 days later
- Feline hemoplasmosis (Mycoplasma haemofelis, M. haemominutum) ยท 5 mg/kg ยท IM, SC ยท every 14 days ยท until able to maintain a normal PCV ยท Alternative for cats intolerant of doxycycline.
- Feline clinical ehrlichiosis or anaplasmosis ยท 5 mg/kg ยท IM ยท every 14 days ยท for at least 2-4 treatments ยท Alternative to doxycycline.
- Treatment of large babesial species infection ยท 2.5 mg/kg ยท IM ยท once ยท 1 dose ยท Dose based on imidocarb dipropionate. Can improve clinical signs. Alternative agents are preferable for smaller species (e.g., B. felis).
- Babesiosis ยท 1.2 mg/kg ยท IM ยท repeat in 10-14 days
- Equine piroplasmosis (Babesia caballi; Babesia equi) ยท 2.2 mg/kg ยท IM ยท once ยท Will generally allow clinical signs to subside.
- Equine piroplasmosis (Babesia caballi) ยท 2 mg/kg ยท IM ยท once a day ยท for 2 days ยท To eliminate B. caballi.
Routes of administration
Contraindications
- Intravenous (IV) administration
- Patients exposed to cholinesterase-inhibiting drugs
- Patients exposed to pesticides or certain chemicals
Adverse effects
- Pain and inflammation at the injection site (rarely ulceration)
- Salivation/drooling
- Nasal drip/discharge
- Vomiting (usually brief)
- Panting
- Diarrhea
- Restlessness
- Lacrimation and sweating (horses)
- Severe renal tubular or hepatic necrosis (rare)
- Salivation (drooling)
- Vomiting
- Injection site inflammation (mild to severe, potential ulceration)
- Anaphylactoid reactions (reported in cattle)
Drug interactions
- Cholinesterase-inhibiting drugs (e.g., pyridostigmine) ยท Increased risk of severe cholinergic toxicity; concurrent use is contraindicated.
- Pesticides and chemicals ยท May exacerbate cholinergic adverse effects and toxicity.
- Anticholinesterases ยท Increased risk of severe cholinergic toxicity ยท major
Monitoring
- Clinical efficacy (resolution of parasitemia and clinical signs)
- Adverse effect profile (cholinergic signs, injection site reactions)
- Creatine kinase (CK) levels (may be significantly increased post-IM injection)
- Liver and kidney function (especially in cases of suspected overdose or pre-existing disease)
- Resolution of clinical signs of babesiosis (fever, anemia, lethargy)
- Blood smears or PCR to confirm parasite clearance
- Injection site for signs of inflammation, necrosis, or ulceration
- Immediate post-injection monitoring for cholinergic crisis
Overdose
**Acute Toxicity & Overdose Signs:** - **Dogs**: At 1.5X the labeled dose (9.9 mg/kg), dogs exhibited signs of liver injury (mildly elevated liver enzymes), pain/swelling at the injection site, and vomiting. - **General Overdose/Chronic Toxicity**: Presents primarily with severe **cholinergic signs** (vomiting, weakness, lethargy, excessive salivation) or adverse changes in liver, kidney, lung, or intestinal function. - **Horses**: The reported LD-50 is 16 mg/kg. **Treatment:** - **Atropine** or other antimuscarinics may be highly useful to treat the cholinergic signs associated with imidocarb toxicity. - Provide symptomatic and supportive care for organ dysfunction.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.