# Eprinomectin: veterinary dose and monograph

> Eprinomectin is a veterinary antiparasitic. Avermectin (macrocyclic lactone) endectocide whose standout feature is ZERO MILK WITHHOLDING in dairy cattle — the only broad endectocide that can be used in lactating dairy cows without discarding milk. Indications include bovine GI nematodes (Ostertagia, Cooperia, Haemonchus, etc.); lungworm (Dictyocaulus); mites (mange), lice, cattle grubs, horn flies. This monograph lists 8 reference doses for cats, cattle, horses, goats and sheep, each with route, frequency and source, plus meat and milk withdrawal periods for food animals.

Source: https://vetmasterji.com/drugs/eprinomectin · Last reviewed: 2026-10-01

## At a glance

- **Drug class:** Antiparasitic
- **Also known as:** Eprinex, LongRange, Eprecis
- **Species with doses:** Cats, Cattle, Horses, Goats and Sheep
- **General dose range:** 0.5 mg/kg Topical single dose (repeat per cycle) — check the species tables for the indication
- **Routes:** Topical, SC
- **Last reviewed:** 1 October 2026

## Indications

- Bovine GI nematodes (Ostertagia, Cooperia, Haemonchus, etc.)
- Lungworm (Dictyocaulus)
- Mites (mange), lice, cattle grubs, horn flies
- Parasite control in LACTATING dairy cattle (zero milk withdrawal)

## Eprinomectin dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

### Cats

*Eprinomectin doses for cats*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Heartworm prevention / worms (with praziquantel, topical) | 0.5 mg/kg | Topical | monthly | — |

- Heartworm prevention / worms (with praziquantel, topical): Papich 5e: 0.5 mg/kg eprinomectin with 10 mg/kg praziquantel applied to the skin. Use the combination product’s weight bands.

### Cattle

*Eprinomectin doses for cattle*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Endo/ectoparasites (pour-on) | 0.5 mg/kg | Topical | single application | — | no slaughter withdrawal / no milk discard |
| Extended-release control (LongRange injectable) | 1 mg/kg | SC | single dose (season-long) | — | 48d slaughter |

- Endo/ectoparasites (pour-on): Papich 5e and Plumb’s p.476 (Eprinex label): 0.5 mg/kg (1 mL/10 kg) along the backline from withers to tailhead, beef and dairy cattle. US label: no meat or milk withdrawal. Check the local label.
- Extended-release control (LongRange injectable): Papich 5e: 1 mg/kg SC (extended-release injection). US label slaughter withdrawal 48 days; not for female dairy cattle 20 months or older or veal calves.

### Horses

*Eprinomectin doses for horses*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Psoroptic mange (P. equi) | 0.5 mg/kg | Topical | once weekly × 4 | — |

- Psoroptic mange (P. equi): Plumb’s p.476 (Ural 2008): 0.5 mg/kg topically once weekly for 4 treatments; obtain informed consent. Papich 5e: doses for horses otherwise not established.

### Goats

*Eprinomectin doses for goats*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| GI / pulmonary nematodes — injection | 0.2–0.4 mg/kg | SC | single dose | — | Withdrawal NOT established — treat as extra-label |
| GI / pulmonary nematodes — pour-on | 1 mg/kg | Topical | single application | — | Withdrawal NOT established — treat as extra-label |

- GI / pulmonary nematodes — injection: Plumb’s 10e p.469 (extra-label): GI nematodes in NON-LACTATING goats 0.2–0.4 mg/kg SC; GI and pulmonary nematodes in sheep and goats 0.2 mg/kg SC. Papich 5e gives no goat dose. No goat withdrawal is printed — obtain a FARAD estimate.
- GI / pulmonary nematodes — pour-on: Plumb’s 10e p.469 (extra-label): 1 mg/kg topically in a narrow strip from the withers to the tailhead. This dose may be SUBOPTIMAL in goats because topical bioavailability is low and variable. Obtain a FARAD withdrawal.

### Sheep

*Eprinomectin doses for sheep*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| GI / pulmonary nematodes — injection | 0.2 mg/kg | SC | single dose | — | Withdrawal NOT established — treat as extra-label |
| GI / pulmonary nematodes — pour-on | 1 mg/kg | Topical | single application | — | Withdrawal NOT established — treat as extra-label |

- GI / pulmonary nematodes — injection: Plumb’s 10e p.469 (extra-label): GI and pulmonary nematodes in sheep and goats 0.2 mg/kg SC. Papich 5e gives no sheep dose. No sheep withdrawal is printed — obtain a FARAD estimate.
- GI / pulmonary nematodes — pour-on: Plumb’s 10e p.469 (extra-label): 1 mg/kg topically in a narrow strip from the withers to the tailhead. Obtain a FARAD withdrawal.

### Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

*Eprinomectin doses for buffalo*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Endo/ectoparasites (pour-on) | 0.5 mg/kg | Topical | single application | — | no slaughter withdrawal / no milk discard |
| Extended-release control (LongRange injectable) | 1 mg/kg | SC | single dose (season-long) | — | 48d slaughter |

- Endo/ectoparasites (pour-on): Papich 5e and Plumb’s p.476 (Eprinex label): 0.5 mg/kg (1 mL/10 kg) along the backline from withers to tailhead, beef and dairy cattle. US label: no meat or milk withdrawal. Check the local label.
- Extended-release control (LongRange injectable): Papich 5e: 1 mg/kg SC (extended-release injection). US label slaughter withdrawal 48 days; not for female dairy cattle 20 months or older or veal calves.

## Contraindications

Off-label species without dose verification. Accidental exposure of MDR1-mutant dogs (this is a cattle product). Environmental release near waterways (aquatic toxicity). Observe meat withdrawal (milk: zero for the licensed pour-on). Known hypersensitivity.

## Species-specific warnings

> **Caution:** Dogs: A cattle macrocyclic lactone — MDR1 (ABCB1-1Δ) breeds are highly sensitive to accidental ingestion. Keep away from dogs.

## Adverse effects

- Transient local reaction at pour-on/injection site
- Neurotoxicity only at gross overdose or in MDR1-deficient animals
- Environmental toxicity to dung beetles and aquatic invertebrates

## Drug interactions

- P-glycoprotein inhibitors: increased CNS exposure/toxicity risk
- Concurrent CNS depressants: additive at high exposure
- No significant interaction at label doses in cattle

## Pregnancy and lactation

Safe in pregnant/lactating cattle at label doses — indeed it is the endectocide of choice for milking dairy cows.

## Monitoring

- Clinical efficacy / faecal egg count reduction
- Meat withdrawal compliance (milk zero for licensed pour-on)
- Resistance surveillance (FECRT)
- Neurological status only if overdose suspected

## Toxicity and overdose

Very wide margin; toxicity (mydriasis, ataxia, tremor, depression, coma) only at gross overdose or in MDR1-deficient animals. Environmental toxicity to dung fauna/aquatic invertebrates is a class concern.

Management: No specific antidote. Supportive/intensive care; benzodiazepines for seizures; intravenous lipid emulsion for severe macrocyclic-lactone neurotoxicity. Recovery may take days–weeks.

## Clinical pearls

- THE endectocide for milking dairy cows — zero milk withholding is its defining advantage
- Pour-on for routine deworming; LongRange injectable for season-long control (but longer meat withdrawal)
- Same macrocyclic-lactone cautions: MDR1 dogs (keep away), dung beetle/aquatic toxicity, and rotate classes to slow resistance
- Goats clear it fast and have no established withdrawal — dose and withhold conservatively

## Mechanism of action

Binds glutamate-gated chloride channels (and GABA channels) in nematode and arthropod neuromuscular tissue, causing chloride influx, hyperpolarisation, paralysis and death. Mammals are spared (channels behind the blood–brain barrier; P-glycoprotein efflux). It was specifically selected/formulated for very low milk partitioning, which underlies the zero milk-withhold claim.

## Formulations and products

- Pour-on 5 mg/mL (0.5 %)
- Injectable 20 mg/mL (extended-release, LongRange)
- Eprinex Pour-On (Boehringer Ingelheim (Merial)) — 5 mg/mL (0.5 %), Pour-on
- LongRange (Boehringer Ingelheim) — 20 mg/mL extended-release, SC injection

## Storage

Store 15–30 °C, protect from light/frost. Keep away from waterways (aquatic toxicity).

## Before you use this dose

> **Caution:** Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

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## Frequently asked questions

### What is the dose of Eprinomectin for cats?

Reference doses for Eprinomectin in cats: 0.5 mg/kg Topical monthly (Heartworm prevention / worms (with praziquantel, topical)). Confirm against the label and the patient before use.

### What is the dose of Eprinomectin for cattle?

Reference doses for Eprinomectin in cattle: 0.5 mg/kg Topical single application (Endo/ectoparasites (pour-on)); 1 mg/kg SC single dose (season-long) (Extended-release control (LongRange injectable)). Confirm against the label and the patient before use.

### What is the dose of Eprinomectin for horses?

Reference doses for Eprinomectin in horses: 0.5 mg/kg Topical once weekly × 4 (Psoroptic mange (P. equi)). Confirm against the label and the patient before use.

### What is the withdrawal period for Eprinomectin?

Cattle, Topical (Endo/ectoparasites (pour-on)): no slaughter withdrawal / no milk discard; Cattle, SC (Extended-release control (LongRange injectable)): 48d slaughter; Goats, SC (GI / pulmonary nematodes — injection): Withdrawal NOT established — treat as extra-label; Goats, Topical (GI / pulmonary nematodes — pour-on): Withdrawal NOT established — treat as extra-label; Sheep, SC (GI / pulmonary nematodes — injection): Withdrawal NOT established — treat as extra-label; Sheep, Topical (GI / pulmonary nematodes — pour-on): Withdrawal NOT established — treat as extra-label. Follow the product label and national regulations where they differ.

### When should Eprinomectin not be used?

Off-label species without dose verification. Accidental exposure of MDR1-mutant dogs (this is a cattle product). Environmental release near waterways (aquatic toxicity). Observe meat withdrawal (milk: zero for the licensed pour-on). Known hypersensitivity.

### What are the side effects of Eprinomectin in animals?

Transient local reaction at pour-on/injection site; Neurotoxicity only at gross overdose or in MDR1-deficient animals; Environmental toxicity to dung beetles and aquatic invertebrates.

## Sources

- Plumb's Veterinary Drug Handbook
- Merck Veterinary Manual, 11th edition
- Papich, Papich Handbook of Veterinary Drugs, 5th edition

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VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.