Dichlorvos
2,2-dichlorovinyl dimethyl phosphate (DDVP)
Also known as: Atgard · Ravap E.C. · Vapona No Pest Strip · DDVP · 2,2-dichlorovinyl dimethyl phosphate · NSC-6738 · OMS-14 · SD-1750
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
Small Mammals
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Ectoparasite control | Hang 5 cm of a dichlorvos strip (e.g., Vapona No Pest Strip) 6 inches above cage for 24 hours, twice weekly for 3 weeks; OR hang in room for 24 hours once a week for 6 weeks; OR a 1 inch square laid on cage for 24 hours once a week for 6 weeks | Environmental | Twice weekly or once weekly | 3 to 6 weeks | 🌎 NA |
- Ectoparasite control: For Mice, Rats, Gerbils, Hamsters, Guinea pigs, Chinchillas
Swine
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Internal parasites (Ascaris, Trichuris, Ascarops strongylina, Oesophagostomum spp.) | Specific amounts of feed per packet are dependent on pig weight. See the label for specific recommendations. | PO | Once | Single treatment | 🌎 NA |
- Internal parasites (Ascaris, Trichuris, Ascarops strongylina, Oesophagostomum spp.): Administered by adding to feed (crumble-type or dry meal).
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Dichlorvos (often abbreviated as DDVP) is a highly volatile organophosphate compound historically used as a broad-spectrum anthelmintic and ectoparasiticide.
- Veterinary Use: Primarily utilized as an oral dewormer in swine (targeting roundworms, whipworms, and nodular worms) and as an environmental ectoparasiticide (e.g., 'No Pest Strips') for small mammals and premise fly control.
- Historical Context: While it was once available for internal use in dogs, cats, and horses, it has been entirely replaced in these species by newer, safer, and more effective anthelmintics (such as macrocyclic lactones and benzimidazoles).
Clinical Pearl: Because dichlorvos is highly volatile, it is uniquely suited for use in resin strips that slowly release the chemical into the air to control flying insects and ectoparasites in enclosed spaces.
Mechanism of action
Dichlorvos acts by phosphorylating and inhibiting the enzyme acetylcholinesterase (AChE).
- AChE Inhibition → Prevents the breakdown of the neurotransmitter acetylcholine (ACh).
- ACh Accumulation → Continuous overstimulation of nicotinic and muscarinic receptors at the neuromuscular junction and autonomic synapses.
- In susceptible parasites, this sustained depolarization leads to spastic paralysis and subsequent death.
Pharmacological Note: Organophosphate binding to AChE can become irreversible over time through a process called "aging." Prompt treatment of toxicity is required before aging occurs.
Safety & warnings
Contraindications
- Concurrent use of other cholinesterase-inhibiting drugs, pesticides, or chemicals
- Allowing fowl access to medicated feed or manure from treated animals
Adverse effects
- Vomiting
- Tremors
- Bradycardia
- Respiratory distress
- Hyperexcitability
- Salivation
- Diarrhea
Precautions
Avoid contact with the skin and keep strictly out of reach of children. Unused medication or medicated feed should be buried 18 inches below the ground and covered so that it is unavailable to any other animal. Do not use within a few days of any other cholinesterase-inhibiting drug, pesticide, or chemical.
Drug interactions
May potentiate organophosphate toxicity; should not be given within one month of worming with an organophosphate.
Additive cholinesterase inhibition; avoid concurrent use.
Has anticholinesterase activity; avoid concurrent use with organophosphates.
Can inhibit cholinesterase; avoid concurrent use.
Adverse effects could be intensified if used concomitantly.
Prolonged neuromuscular blockade; do not use depolarizing muscle relaxants for at least 48 hours after organophosphate administration.
Monitoring
- Efficacy (resolution of parasite burden)
- Signs of organophosphate toxicity (SLUDDE signs, tremors, respiratory distress)
Overdose
Toxicity Warning: Organophosphate overdosage causes severe cholinergic crisis, classically remembered by the acronym SLUDDE (Salivation, Lacrimation, Urination, Defecation, Dyspnea, Emesis).
Clinical Signs of Toxicity:
- Vomiting, diarrhea, and hypersalivation.
- Muscle tremors, hyperexcitability, and seizures.
- Bradycardia and severe respiratory distress (bronchoconstriction and increased secretions).
Treatment & Antidotes:
- Atropine: Acts as a muscarinic receptor antagonist to control life-threatening bradycardia, bronchoconstriction, and excessive secretions.
- Pralidoxime (2-PAM): An AChE reactivator that can reverse neuromuscular blockade (tremors/weakness) if administered before the enzyme-toxin complex "ages."
- Avoid: Succinylcholine, theophylline, aminophylline, reserpine, or respiratory depressant drugs (e.g., narcotics, phenothiazines).
- Human Exposure: If ingested by a human, immediately contact a poison control center, physician, or hospital emergency room.
Available products
Formulations
- Feed additive (crumble-type or dry meal)
- Premise spray/liquid
- Resin strips (e.g., No Pest Strip)
Veterinary
- Atgard C (Dichlorvos Feed Additive)
- Atgard Swine Wormer (Dichlorvos Feed Additive)
- Ravap E.C. (Dichlorvos with Tetrachlorvinphos Premise and Topical Insecticide)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store Atgard swine wormer at less than 80°F (26.6°C). Dichlorvos feed additives should not be stored at temperatures below freezing. Dichlorvos is sensitive to hydrolysis and will degrade if exposed to moisture or oxidizing agents.
Client information
Safety First
- Keep out of reach of children and pets. Organophosphates are highly toxic if ingested or absorbed inappropriately.
- Handling of dichlorvos liquid preparations (e.g., premise sprays) must be done with extreme care. Wear gloves, avoid skin contact, and strictly follow all label directions.
For Swine Owners
- When using the oral dewormer pellets, you may notice the non-digestible pellets passing in the animals' feces. This is completely normal and does not mean the medication failed to work.
- Do not allow poultry or wild birds access to the medicated feed or the manure from treated animals.
- Bury any unused medicated feed at least 18 inches underground to prevent accidental poisoning of other animals.
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.