# Ivermectin for Animals: Mechanism, Doses by Species & Brands

> Ivermectin is a macrocyclic lactone antiparasitic used against roundworms and external parasites such as mites, lice and ticks. In cattle it is given at 200 mcg/kg by subcutaneous injection; in dogs it…

- Source page: https://wevet.in/active-ingredients/ivermectin/
- Type: Active ingredient
- Publisher: WeVet
- Updated: 2026-11-02
- Medically reviewed by: Dr. Ravi Baraiya, B.V.Sc. (2026-11-02)
- Audience: veterinarians and veterinary students

Ivermectin is a macrocyclic lactone antiparasitic used against roundworms and external parasites such as mites, lice and ticks [1][3]. In cattle it is given at 200 mcg/kg by subcutaneous injection [3]; in dogs it is used at very low doses for heartworm prevention [4] and, extra-label, at much higher doses for mange [1].

- Class: Macrocyclic lactone (avermectin) antiparasitic
- Brands: Heartgard Plus, Hitek, Hitek F, Hitek Platinum, Ivomec, Neomec

## Dose by species

| Species | Use | Dose | Route | How often | Basis |
|---|---|---|---|---|---|
| Dogs | Heartworm prevention (with pyrantel, as Heartgard Plus) (Minimum dose on the label; given as whole chewables by weight band.) | 6 mcg/kg [4] | PO | Once a month | Label |
| Dogs | Sarcoptic mange (extra-label) (Contraindicated in avermectin-sensitive breeds at this dose.) | 200 mcg/kg [1] | PO or SC | 2–4 treatments, 2 weeks apart | Reference |
| Dogs | Generalized demodicosis (extra-label) (Increase the dose gradually and monitor closely. Contraindicated in Collies and Collie crosses; MDR1 (ABCB1) testing may be required.) | 300–600 mcg/kg [1] | PO | Once daily | Reference |
| Cattle | Internal and external parasites (Ivomec 1% label: 1 mL per 50 kg.) | 200 mcg/kg [3] | SC | Single dose | Label |
| Pigs | Internal and external parasites (Ivomec 1% label: 1 mL per 33 kg.) | 300 mcg/kg [3] | SC (neck) | Single dose | Label |

## Uses

- Cattle: gastrointestinal roundworms, lungworms, grubs, sucking lice and mange mites; swine: gastrointestinal roundworms, lungworms, lice and mange mites (Ivomec 1% injection label) [3].
- Dogs: prevention of heartworm disease at 6 mcg/kg once a month (Heartgard Plus label) [4].
- Dogs, extra-label: sarcoptic mange and generalized demodicosis [1].

## Mechanism of action

Macrocyclic lactones act by binding to glutamate-gated chloride channel receptors in nematode and arthropod nerve cells [2]. Compounds of the class bind selectively and with high affinity to glutamate-gated chloride ion channels in invertebrate nerve and muscle cells, resulting in paralysis and death of the parasite [3].

## Safety

- Ivermectin is contraindicated in Collies and Collie crosses at the doses used for demodicosis, and idiosyncratic toxicity may be seen in any breed [1].
- Testing for mutation in the MDR1 allele (ABCB1) may be required before starting ivermectin therapy for demodicosis [1].
- The cattle/swine injection should not be used in other animal species, as severe adverse reactions, including fatalities in dogs, may result [3].
- At the heartworm-prevention dose, Heartgard showed no signs of toxicity at 10 times the recommended dose (60 mcg/kg) in sensitive Collies [4].

## Withdrawal periods

- Cattle, meat: 35 days — Ivomec 1% injection (US label): do not treat cattle within 35 days of slaughter. [3]
- Cattle, milk: check pack — Ivomec 1% injection (US label): withdrawal in milk not established — do not use in female dairy cattle of breeding age. [3]
- Pigs, meat: 18 days — Ivomec 1% injection (US label): do not treat swine within 18 days of slaughter. [3]

## Frequently asked questions

### What is the ivermectin dose for dogs?

For heartworm prevention the labelled minimum is 6 mcg/kg once a month [4]. Extra-label, references give 200 mcg/kg PO or SC for sarcoptic mange (2–4 treatments 2 weeks apart) and 300–600 mcg/kg/day PO for generalized demodicosis, increased gradually [1].

### Is ivermectin safe for Collies?

At mange doses ivermectin is contraindicated in Collies and Collie crosses, toxicity may occur in any breed, and MDR1 (ABCB1) testing may be required [1].

### What is the ivermectin dose for cattle?

200 mcg/kg by subcutaneous injection, which is 1 mL per 50 kg of a 1% (10 mg/mL) injection [3].

## References

[1] Mange in Dogs and Cats — Merck Veterinary Manual — M. W. Dryden (reviewed 2023, updated May 2025) (2025). https://www.merckvetmanual.com/integumentary-system/mange/mange-in-dogs-and-cats
[2] Pharmacodynamics: Mechanisms of Anthelmintic Action in Animals — Merck Veterinary Manual — E. Claerebout & C. E. Lanusse (Apr 2025) (2025). https://www.merckvetmanual.com/pharmacology/anthelmintics/pharmacodynamics-mechanisms-of-anthelmintic-action-in-animals
[3] IVOMEC (ivermectin) injection, solution — label — DailyMed (US NLM) — FDA-approved label, Boehringer Ingelheim (2026). https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=84fe39b2-0423-479a-b81f-198e2fb4e826
[4] HEARTGARD PLUS (ivermectin and pyrantel pamoate) chewable — label — DailyMed (US NLM) — FDA-approved label, Boehringer Ingelheim (2026). https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=595a4883-6b37-4190-9579-a2c7ca4738eb

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Numbers in [brackets] cite the references above. For veterinary professionals. Information supports — never replaces — clinical judgement; always check the current product label and local regulations.
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