Doramectin
25-cyclohexyl-5-O-demethyl-25-de(1-methylpropyl)avermectin A1a
Also known as: Dectomax · UK-67994
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
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Treatment of generalized demodicosis | 600 micrograms/kg | PO | once daily | Until 60 days without improvement | 🌎 NA |
| Treatment of generalized demodicosis | 600 micrograms/kg (0.6 mg/kg) | SC | once per week | — | 🌎 NA |
| Treatment of benign nodules secondary to S. lupi | 400 micrograms/kg | SC | once at two week intervals | once | 🌎 NA |
- Treatment of generalized demodicosis: Extra-label. If improvement is not seen after 60 days, an alternative therapy should be used.
- Treatment of generalized demodicosis: Extra-label. Get informed consent from owner.
- Treatment of benign nodules secondary to S. lupi: May use milbemycin in MDR-1 sensitive breeds.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Feline demodicosis (D. cati, D. gatoi) | 600 micrograms/kg (0.6 mg/kg) | SC | once per week | — | 🌎 NA |
- Feline demodicosis (D. cati, D. gatoi): Extra-label. Get informed consent from owner. Alternative treatments include Lime sulfur dips or amitraz.
Small Mammals
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| P. cuniculi infestations (Rabbits) | 200 micrograms/kg | IM | once | once | 🌎 NA |
Cattle
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Labeled indications (Injectable) | 200 micrograms/kg (1 mL per 110 lb. body weight) | SC/IM | once | — | 🌎 NA |
| Labeled indications (Pour-on) | 500 micrograms/kg (1 mL per 22 lb. body weight) | topical | once | — | 🌎 NA |
- Labeled indications (Injectable): Beef Quality Assurance guidelines recommend SC administration as the preferred route.
- Labeled indications (Pour-on): Administer topically along the mid-line of the back in a narrow strip between the withers and tailhead.
Swine
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Labeled indications | 300 micrograms/kg (1 mL per 75 lb. body weight) | IM | once | — | 🌎 NA |
- Labeled indications: Intramuscular injections should be administered into the muscular region of the neck.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Doramectin is a macrocyclic lactone belonging to the avermectin class of antiparasitic agents.
- Food Animal Use: FDA-approved as an injectable and topical pour-on for cattle and swine to treat a wide variety of gastrointestinal nematodes, lungworms, eyeworms, grubs, lice, and mange mites.
- Companion Animal Use: Used extra-label in dogs and cats primarily for the treatment of generalized demodicosis and spirocercosis.
Clinical Pearl: While highly effective, its use in small animals is strictly off-label and carries a risk of severe neurotoxicity, particularly in herding breeds with the MDR1 (ABCB1) mutation.
Mechanism of action
Doramectin exerts its antiparasitic effect by binding to glutamate-gated chloride channels found in invertebrate nerve and muscle cells.
- Mechanism: Binding → increases membrane permeability to chloride ions → cellular hyperpolarization → flaccid paralysis and death of the parasite.
- It also enhances the release of gamma-aminobutyric acid (GABA) at presynaptic neurons, further inhibiting nerve transmission.
- Mammalian Safety: Mammals lack glutamate-gated chloride channels, and avermectins typically do not cross the intact mammalian blood-brain barrier (where GABA receptors reside) due to the P-glycoprotein efflux pump. Toxicity occurs when this pump is deficient (e.g., MDR1 mutation) or overwhelmed by massive overdoses.
Safety & warnings
Contraindications
- Dogs with MDR1-allele mutations (relative/absolute depending on dose)
- Female dairy cattle 20 months of age or older
- Calves to be processed for veal
Adverse effects
- Injection site blemishes (IM administration)
- Pupil dilation (mydriasis) in dogs
- Lethargy
- Blindness
- Coma (especially in MDR1-mutant dogs)
Precautions
The manufacturer warns against use in unapproved species due to potential severe adverse reactions (including fatalities in dogs). Extreme caution or avoidance is recommended in herding breeds susceptible to the MDR1 (ABCB1) mutation (e.g., Collies, Australian Shepherds, Shelties, Long-haired Whippets) due to a significantly higher risk for severe neurotoxicity.
Monitoring
- Clinical efficacy (resolution of parasites/lesions)
- Signs of neurotoxicity in off-label species (dogs/cats)
Pharmacokinetics
Absorption
Bioavailability is, for practical purposes, equal with SC and IM injections in cattle. After SC injection, time to peak plasma concentration in cattle is about 5 days.
Distribution
Does not readily cross the blood-brain barrier where mammalian GABA receptors occur.
Overdose
In field trials, no toxic signs were seen in cattle given up to 25X the recommended dose. In breeding animals (bulls, and cows in early and late pregnancy), a dose 3 times the recommended dose had no effect on breeding performance.
Available products
Formulations
- Injectable solution
- Topical pour-on solution
Veterinary
- Doramectin Injectable Solution: 10 mg/mL in 100 mL, 250 mL, and 500 mL multi-dose vials (Dectomax)
- Doramectin Pour-On Solution: 5 mg/mL in 250 mL, 1 L, 2.5 L and 5 L multidose containers (Dectomax Pour-On)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
The injectable solution should be stored below 86°F (30°C). The topical pour-on solution should be stored below 30°C (86°F) and protected from light.
Client information
- Administration: Read and follow all labeled instructions carefully. If using off-label for a dog or cat, ensure you understand the risks discussed by your veterinarian.
- Toxicity Warning: Watch closely for signs of toxicity in dogs and cats, such as dilated pupils, extreme lethargy, stumbling, blindness, or unresponsiveness. Contact your vet immediately if these occur.
- Food Animal Withdrawals:
- Cattle: Must not be slaughtered for human consumption within 35-45 days of treatment (check specific product label).
- Swine: Should not be slaughtered for human consumption within 24 days of treatment.
- Restrictions: Not for use in female dairy cattle 20 months of age or older. Should not be used in calves to be processed for veal. A withdrawal period has not been established in preruminating calves.
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.