Doramectin: veterinary dose and monograph

At a glance

Drug class

Antiparasitic

Also known as

Dectomax

Species with doses

Dogs, Cats, Cattle, Pigs and Rabbits

General dose range

0.2 mg/kg SC single dose (repeat per parasite cycle) — check the species tables for the indication

Routes

SC, Topical, IM

Last reviewed

1 October 2026

Indications

• Bovine GI nematodes (Ostertagia, Cooperia, Haemonchus, etc.)
• Lungworm (Dictyocaulus)
• Cattle grubs (Hypoderma), sucking lice, mange mites (Psoroptes, Sarcoptes)
• Swine: GI nematodes, lice, mange (Sarcoptes)
• Sheep/goat GI nematodes (off-label in goats — adjust dose)

Doramectin 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.

Dogs

• Generalised demodicosis (extra-label): Papich 5e: 600 µg/kg once weekly SC or PO for 5–23 weeks. Plumb’s p.440: 600 µg/kg SC weekly (Hillier 2006) or PO daily (Merchant 2009) — change therapy if no improvement by 60 days. Spirocerca nodules 400 µg/kg SC. Toxic in ABCB1 (MDR1) mutant dogs — test first; informed consent. (600 µg/kg = 0.6 mg/kg.)

Cats

• Mites (incl. demodicosis) — extra-label: Papich 5e: mite infection 200–270 µg/kg once SC (0.1 mL of 1% solution per cat). Plumb’s p.440 (Hillier 2006): D. cati / D. gatoi 600 µg/kg SC once weekly. Informed consent. (200–600 µg/kg = 0.2–0.6 mg/kg.)

Cattle

• Endo/ectoparasites (injectable): Papich 5e and Plumb’s p.440 (Dectomax label): 0.2 mg/kg (1 mL/50 kg) SC or IM — SC in front of or behind the shoulder preferred (BQA). US label slaughter withdrawal 45 days; not for female dairy cattle 20 months or older or veal calves. Check the local label withdrawal.
• Endo/ectoparasites (pour-on): Papich 5e and Plumb’s p.440 (Dectomax Pour-On label): 0.5 mg/kg (1 mL per 10 kg) along the dorsal midline from withers to tailhead; US slaughter withdrawal 45 days.

Goats

• No reference dose for this species: Neither Papich 5e nor Plumb’s gives a doramectin dose for goats; the previous row extrapolated a higher dose with no source.

Sheep

• No reference dose for this species: Neither Papich 5e nor Plumb’s gives a doramectin dose for sheep (Plumb’s: FDA-approved for cattle and swine). Where a sheep label exists locally, follow that label and its withdrawal.

Pigs

• GI nematodes, mange, lice: Papich 5e and Plumb’s (Dectomax label): 300 µg/kg (0.3 mg/kg; 1 mL per 34 kg) IM in the neck, single injection. US label slaughter withdrawal 24 days.

Buffalo

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

• Endo/ectoparasites (injectable): Papich 5e and Plumb’s p.440 (Dectomax label): 0.2 mg/kg (1 mL/50 kg) SC or IM — SC in front of or behind the shoulder preferred (BQA). US label slaughter withdrawal 45 days; not for female dairy cattle 20 months or older or veal calves. Check the local label withdrawal.
• Endo/ectoparasites (pour-on): Papich 5e and Plumb’s p.440 (Dectomax Pour-On label): 0.5 mg/kg (1 mL per 10 kg) along the dorsal midline from withers to tailhead; US slaughter withdrawal 45 days.

Rabbits

• Psoroptes cuniculi (ear mites): Plumb’s p.440 (Kanbur 2008): 200 µg/kg IM once. (= 0.2 mg/kg.)

Contraindications

Not licensed for lactating dairy animals producing milk for human consumption (long residues). Avoid high/overdose exposure in MDR1-mutant dogs (Collies, Australian Shepherds — though doramectin is a cattle/pig drug, accidental ingestion is a risk). Do not use in species/withdrawal situations off-label without verifying residues.

Species-specific warnings

Dogs: Macrocyclic lactone — MDR1 (ABCB1-1Δ) breeds (Collie, Australian Shepherd, etc.) are exquisitely sensitive to overdose/accidental ingestion (coma, death). This is a livestock product; keep away from dogs.

Goats: Off-label in goats; requires a higher dose and has no established withdrawal — extend meat withdrawal conservatively.

Adverse effects

• Transient injection-site swelling/discomfort
• Neurotoxicity (ataxia, tremor, mydriasis, coma) only at gross overdose or in MDR1-deficient animals
• Environmental: toxic to dung beetles and aquatic invertebrates

Drug interactions

• Other P-glycoprotein substrates/inhibitors (e.g. spinosad, ketoconazole): increased CNS exposure / toxicity
• Concurrent GABA-ergic CNS depressants: potential additive CNS depression at high exposure
• No significant interaction at label doses in target food species

Pregnancy and lactation

Considered safe in pregnant cattle, sheep and pigs at label doses; widely used in breeding stock.

Monitoring

• Clinical efficacy / faecal egg count reduction
• Neurological status if overdose suspected or in at-risk breeds
• Strict meat/withdrawal compliance (35–56 days depending on form/species)
• Resistance surveillance (FECRT) — macrocyclic-lactone resistance is rising in small ruminants

Toxicity and overdose

Very wide margin in normal animals. Toxicity (mydriasis, drooling, ataxia, tremor, depression, blindness, coma) appears only at large overdoses or in MDR1 (ABCB1-1Δ) individuals. Environmental toxicity to dung-dwelling insects and aquatic invertebrates is a recognised concern with macrocyclic lactones.

Management: No specific antidote. Supportive/intensive care — IV fluids, thermoregulation, nursing; control seizures with benzodiazepines. Intravenous lipid emulsion (ILE) is used for severe macrocyclic-lactone neurotoxicity (lipophilic drug). Recovery may take days to weeks.

Clinical pearls

• Longer persistent activity than ivermectin — good for season-long parasite control in cattle
• Goats need a higher mg/kg than sheep (faster metabolism) and have no established withdrawal — use cautiously
• Not for lactating dairy cows producing human milk — residues are prolonged
• Rotate anthelmintic classes (don't rely on macrocyclic lactones alone) to slow resistance
• Dispose of dung/run-off responsibly — these drugs harm dung beetles and aquatic life

Mechanism of action

Binds glutamate-gated chloride channels (and to a lesser extent GABA-gated channels) in invertebrate nerve and muscle, causing sustained chloride influx, hyperpolarisation, paralysis and death of nematodes and arthropods. Mammals are spared because these channels are confined to the CNS behind the blood–brain barrier and P-glycoprotein normally pumps the drug out — the basis of MDR1 sensitivity.

Formulations and products

• Injectable 10 mg/mL (1 %)
• Pour-on 5 mg/mL (0.5 %)
• Dectomax injectable (Zoetis) — 10 mg/mL (1 %), SC/IM injection
• Dectomax Pour-On (Zoetis) — 5 mg/mL (0.5 %), Pour-on

Storage

Store 15–30 °C, protect from light; do not freeze. Pour-on: keep from frost. Dispose of containers away from waterways (aquatic toxicity).

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

• Dichlorvos (DDVP)
• Diclazuril
• Diethylcarbamazine (DEC)
• Diminazene Diaceturate
• Emodepside
• Eprinomectin
• Epsiprantel
• Febantel

Frequently asked questions