Monepantel: veterinary dose and monograph

At a glance

Drug class

Antiparasitic

Also known as

Zolvix

Species with doses

Sheep

General dose range

2.5 mg/kg PO single dose (repeat per cycle) — check the species tables for the indication

Routes

PO

Last reviewed

1 October 2026

Indications

• Gastrointestinal nematodes of sheep — including benzimidazole/ML/levamisole-resistant strains (Haemonchus, Teladorsagia, Trichostrongylus, etc.)
• Quarantine ("knock-out") drench for incoming sheep to prevent importing resistant worms
• Refractory parasitism where other classes have failed

Monepantel 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.

Goats

• No reference dose for this species: Neither Papich 5e nor Plumb’s has a monepantel monograph, and the previous goat dose was an unsourced extrapolation.

Sheep

• GI nematodes (incl. multidrug-resistant): Label-sourced — neither Papich 5e nor Plumb’s has a monepantel monograph. Zolvix label: 2.5 mg/kg oral drench; follow the local label withdrawal; not for sheep producing milk for human consumption. Reserve for resistant worms / quarantine drenching.

Contraindications

Known hypersensitivity. Routine sole/over-use (preserve the novel class — resistance can develop). Observe meat/milk withdrawal. Off-label use in goats requires dose/withdrawal verification. Lambs below the label minimum age/weight.

Species-specific warnings

Goats: Off-label in goats — higher dose needed and withdrawal not established; extend meat/milk withdrawal conservatively.

Adverse effects

• Very well tolerated at label dose
• Wide safety margin
• No notable host toxicity reported at therapeutic use

Drug interactions

• No clinically important host drug interactions
• No cross-resistance with older anthelmintic classes (its key feature)

Pregnancy and lactation

Considered safe in breeding/pregnant sheep at label doses.

Monitoring

• Faecal egg count reduction test (confirm efficacy and detect emerging resistance)
• Quarantine-drench protocols for incoming stock
• Meat/milk withdrawal compliance
• Refugia/resistance-management practices to preserve the class

Toxicity and overdose

Very wide safety margin in sheep — no significant host toxicity at therapeutic or modestly supratherapeutic doses. The real "risk" is ecological/economic: over-reliance selects for monepantel resistance (already documented on some farms), eroding a last-line class.

Management: Supportive only; no specific antidote needed (wide margin).

Clinical pearls

• A NOVEL-class drench that kills multidrug-resistant sheep worms — invaluable where benzimidazole/ML/levamisole resistance has accumulated
• Use it strategically (quarantine "knock-out" drench, refractory cases) and with refugia/rotation — monepantel resistance has already emerged where overused
• Unique mode of action = no cross-resistance, but that advantage is finite — steward it
• Goats need a higher dose (faster metabolism) with conservative withdrawal

Mechanism of action

An amino-acetonitrile derivative that acts on a NEMATODE-SPECIFIC subunit of the nicotinic acetylcholine receptor (the DEG-3/MPTL-1 family, e.g. MPTL-1/ACR-23), causing sustained receptor activation, hypercontraction/paralysis and death of the worm. Because this target is distinct from those of all older anthelmintic classes, monepantel retains activity against nematodes resistant to benzimidazoles, macrocyclic lactones, imidazothiazoles (levamisole) and tetrahydropyrimidines (pyrantel).

Formulations and products

• Oral drench 25 mg/mL (2.5 %, Zolvix)
• Zolvix (Elanco) — 25 mg/mL (2.5 %) oral drench, Oral drench

Storage

Drench: 15–30 °C, protect from light; shake before use.

Before you use this dose

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.

Other antiparasitics

• Meglumine Antimoniate
• Melarsomine
• Milbemycin oxime
• Monensin
• Morantel
• Moxidectin
• Nicarbazin
• Niclosamide

Frequently asked questions