Eprinomectin
4-epi-acetylamino-4-deoxy-avermectin B1
Also known as: Ivomec Eprinex · Broadline · NexGard Combo (contains eprinomectin) · MK-397 · 4-epi-acetylamino-4-deoxy-avermectin B1 · Eprinomectina · Eprinomectine
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Treatment and prevention of fleas, ticks, nematodes (including feline lungworm and Capillaria plica), and prevention of heartworm disease | Monthly application | topical | monthly | 1 month per application | 🌍 EU |
- Treatment and prevention of fleas, ticks, nematodes (including feline lungworm and Capillaria plica), and prevention of heartworm disease: Apply appropriate pipette size based on cat's body weight.
Small Mammals
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Ear mites (Psoroptes cuniculi) in rabbits | 5 mg/kg topically, twice at 14 day intervals | topical | twice at 14 day intervals | 2 treatments | 🌎 NA |
- Ear mites (Psoroptes cuniculi) in rabbits: One small study (6 subjects) showed partial response.
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Treatment of psoroptic (P. equi) mange | 500 micrograms/kg (0.5 mg/kg) topically once weekly for 4 treatments | topical | once weekly | 4 treatments | 🌎 NA |
- Treatment of psoroptic (P. equi) mange: Author's suggest getting informed consent before use.
Cattle
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Labeled indications (gastrointestinal roundworms, cattle grubs, lice, mange mites, horn flies, lungworms) | 1 mL per 10 kg (22 lb) body weight applied topically along backline in a narrow strip from the withers to the tailhead | topical | once | — | 🌎 NA |
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Eprinomectin is a highly effective avermectin antiparasitic agent primarily used as a topical pour-on solution in cattle. It provides broad-spectrum control against various internal and external parasites, including gastrointestinal roundworms, lungworms, cattle grubs, lice, mange mites, and horn flies.
- Key Advantage: When used as labeled in cattle, it requires zero milk or meat withdrawal times, making it highly convenient for dairy and beef operations.
- Off-label uses: It has shown efficacy in treating Psoroptic mange in horses and ear mites (Psoroptes cuniculi) in rabbits.
Clinical Pearl: As a macrocyclic lactone, it shares a similar safety profile to ivermectin but is specifically formulated for optimal topical absorption in ruminants.
Mechanism of action
Eprinomectin exerts its antiparasitic effect by binding selectively to glutamate-gated chloride ion channels found in invertebrate nerve and muscle cells.
- Mechanism: Binding → Increased cell membrane permeability to chloride ions → Hyperpolarization of the nerve/muscle cell → Paralysis and death of the parasite.
- It also enhances the release of gamma-aminobutyric acid (GABA) at presynaptic neurons, which acts as an inhibitory neurotransmitter, blocking post-synaptic stimulation.
- Safety: Mammals are generally unaffected because they lack glutamate-gated chloride channels, and macrocyclic lactones do not readily cross the mammalian blood-brain barrier (BBB) under normal conditions.
Safety & warnings
Contraindications
- Oral administration
- Intravenous administration
- Cats weighing < 0.6 kg
- Kittens < 7 weeks of age
- Dogs (not intended for use)
Adverse effects
- Ineffectiveness for parasite control (reported in FDA database)
- Anorexia
- Udder hypogalactia
- Mild clumping of the hair at the application site
Precautions
Warning: Do not administer orally or intravenously. Highly toxic to fish and aquatic organisms; dispose of containers properly.
Drug interactions
Potential interaction as both are P-glycoprotein substrates; none reported clinically
Potential interaction as both are P-glycoprotein substrates; none reported clinically
Potential interaction as both are P-glycoprotein substrates; none reported clinically
Potential interaction as both are P-glycoprotein substrates; none reported clinically
Potential interaction as both are P-glycoprotein substrates; none reported clinically
Theoretical potential for interaction due to shared P-glycoprotein efflux pump mechanisms, though none have been clinically reported.
Monitoring
- Clinical efficacy (parasite clearance)
- Adverse reactions (anorexia, milk production in dairy cattle)
- Efficacy of parasite control
- Application site reactions (hair clumping, alopecia, erythema)
Pharmacokinetics
Half-life
Absorption
Absorbed systemically following topical application in cats to provide endoparasitic efficacy.
Distribution
Widely distributed; avermectins generally concentrate in liver and adipose tissue.
Metabolism
Hepatic metabolism.
Elimination
Primarily excreted in feces.
Overdose
Calves given up to 5X dosage showed no signs of adverse effects. One subject (of 6) showed signs of mydriasis when given a 10X dose.
Available products
Formulations
- Topical (Pour-On) Solution: 5 mg/mL
- Topical spot-on solution: 4 mg/ml eprinomectin, fipronil, S-methoprene, and praziquantel (available in 2 pipette sizes)
Veterinary
- Eprinomectin Topical (Pour-On) Solution: 5 mg/mL (Ivomec Eprinex)
- Broadline spot-on solution for cats (UK/EU)
Regulatory status
Withdrawal times: cattle meat 15 days (pour-on) · cattle milk 0 days (pour-on)
Broadline is centrally authorized in the EU.
Classified as POM-V (Prescription Only Medicine - Veterinarian).
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store protected from light and kept at 86°F (30°C) or less. Storage up to 104°F (40°C) is permitted for a short period.
Client information
- Zero Withdrawal: When used as directed in cattle, there is no need to withhold milk or meat.
- Weather Resistant: Rainfall or weather conditions during or after application do not reduce the medication's effectiveness.
- Application Rules: Apply directly to the backline. Do not apply to areas covered with heavy mud or manure, as this can block absorption.
-
Environmental Warning: Eprinomectin is highly toxic to fish and aquatic organisms. Dispose of all empty containers properly (e.g., approved landfill or incineration) and never contaminate water sources.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.