# Animal poisoning: signs, antidotes and first-line treatment

> A quick reference for the 15 poisonings most often seen in practice — including organophosphate / carbamate insecticides, anticoagulant rodenticide, urea / npn toxicity (ammonia poisoning) and nitrate / nitrite poisoning — with the clinical signs, the specific antidote and its dose where one exists, and first-line management. 10 of them have a specific antidote; the rest are managed supportively.

Source: https://vetmasterji.com/toxicology · Last reviewed: 2026-10-01

## Organophosphate / Carbamate insecticides

- **Species:** dogs, cats, cattle, goats and sheep
- **Typical source:** Crop sprays, dips, contaminated feed, malicious poisoning
- **Urgency:** Critical — treat immediately
- **Antidote:** Atropine sulfate
- **Antidote dose:** 0.2–0.5 mg/kg — ¼ IV, remainder SC/IM; repeat to effect (dry secretions). Add pralidoxime (2-PAM) 20 mg/kg slow IV for OPs if available.
- **Also known as:** malathion, chlorpyrifos, carbofuran, OP poisoning

Clinical signs: Hypersalivation (SLUDGE); Miosis; Muscle tremors → paralysis; Diarrhea, urination; Bradycardia; Dyspnea, pulmonary edema.

- Wash off dermal exposure with soap + water
- Do NOT atropinize to fixed dose — titrate to secretions
- Diazepam for seizures
- Avoid phenothiazines

## Anticoagulant rodenticide

- **Species:** dogs and cats
- **Typical source:** Rodent bait ingestion (direct or relay)
- **Urgency:** Urgent
- **Antidote:** Vitamin K1 (phytomenadione)
- **Antidote dose:** 2.5–5 mg/kg/day PO with fatty food, 2–4 weeks (second-generation agents need the full 4 wk); check PT 48 h after stopping.
- **Also known as:** bromadiolone, brodifacoum, warfarin, rat poison

Clinical signs: Lethargy, pallor; Hemorrhage: epistaxis, melena, hematomas; Dyspnea (hemothorax); Signs delayed 2–5 days post-ingestion.

- Emesis if <2–4 h since ingestion
- Activated charcoal 1–4 g/kg
- Whole blood / plasma if actively bleeding
- Avoid IM injections while coagulopathic

## Urea / NPN toxicity (ammonia poisoning)

- **Species:** cattle, buffalo, goats and sheep
- **Typical source:** Fertilizer access, over-supplemented urea feed, poorly mixed ration
- **Urgency:** Critical — treat immediately
- **Antidote:** Cold water + weak acid (vinegar) orally
- **Antidote dose:** 2–6 L of 5% acetic acid (vinegar) + 20–40 L cold water per adult cow via stomach tube; repeat as rumen pH rebounds.
- **Also known as:** non-protein nitrogen, fertilizer ingestion

Clinical signs: Onset 20–60 min; Muscle tremors, ear twitching; Frothy salivation, bloat; Ataxia → recumbency, bellowing; Convulsions, death in 1–2 h.

- Rumenotomy and rumen lavage in valuable animals
- IV isotonic saline + calcium borogluconate for tremors
- Treat herd-mates that shared the feed

## Nitrate / nitrite poisoning

- **Species:** cattle, buffalo, goats and sheep
- **Typical source:** Lush oat/sorghum/sudan fodder, drought-stressed crops, fertilizer runoff water
- **Urgency:** Critical — treat immediately
- **Antidote:** Methylene blue
- **Antidote dose:** 1–2% solution at 4–15 mg/kg slow IV; repeat in 20–30 min if needed (ruminants tolerate repeat dosing).
- **Also known as:** oat hay poisoning, nitrate accumulator plants

Clinical signs: Chocolate-brown mucous membranes and blood; Dyspnea, tachypnea; Weakness, ataxia; Abortion in survivors.

- Minimize stress/handling during crisis
- Remove suspect fodder from the whole herd
- Test remaining fodder before reintroduction

## Snake envenomation (viperine)

- **Species:** dogs, cattle, horses and goats
- **Typical source:** Field grazing, farm dogs — usually face/limb bites
- **Urgency:** Critical — treat immediately
- **Antidote:** Polyvalent anti-snake venom (ASV)
- **Antidote dose:** Species-appropriate polyvalent ASV IV per manufacturer; dose to venom load (not body weight) — pretreat for anaphylaxis risk.
- **Also known as:** russell viper, saw-scaled viper, snake bite

Clinical signs: Rapid painful swelling at bite site; Fang marks, oozing; Coagulopathy: prolonged clotting, hematuria; Hypotension, shock; Neuro signs if elapid (ptosis, paralysis).

- Immobilize patient, keep bite below heart level
- NO tourniquets, incision, or suction
- IV fluids for shock
- Fresh whole blood if coagulopathic
- Tetanus prophylaxis

## Chocolate (theobromine/caffeine)

- **Species:** dogs
- **Typical source:** Dark chocolate, cocoa powder, baking chocolate (dose scales with cocoa %)
- **Urgency:** Urgent
- **Antidote:** No specific antidote — supportive care

Clinical signs: Vomiting, diarrhea (2–4 h); Restlessness, panting; Tachycardia, arrhythmias; Tremors, seizures at high dose.

- Emesis if <2 h (apomorphine 0.03 mg/kg IV)
- Activated charcoal, repeat q4–6h (enterohepatic recycling)
- IV fluids; beta-blocker (propranolol 0.02–0.06 mg/kg slow IV) for tachyarrhythmia
- Diazepam/methocarbamol for tremors

## Paracetamol (acetaminophen)

- **Species:** cats and dogs
- **Typical source:** Well-meaning owner medication — cats are exquisitely sensitive (any dose is toxic)
- **Urgency:** Critical — treat immediately
- **Antidote:** N-acetylcysteine (NAC)
- **Antidote dose:** 140 mg/kg PO/IV loading, then 70 mg/kg q6h × 7 doses. Adjunct: ascorbic acid 30 mg/kg + SAMe.
- **Also known as:** acetaminophen, crocin

Clinical signs: Cats: methemoglobinemia — brown MM, dyspnea, facial/paw edema; Dogs: hepatic necrosis — icterus, vomiting (>100 mg/kg); Chocolate-colored blood.

- Never give paracetamol to cats — client education
- Oxygen for methemoglobinemia
- Hepatoprotectants + IV fluids

## Ivermectin toxicosis

- **Species:** dogs
- **Typical source:** Livestock-strength ivermectin dosed to herding breeds (Collie, Aussie — MDR1 mutation), or massive overdose
- **Urgency:** Urgent
- **Antidote:** IV lipid emulsion (ILE) 20%
- **Antidote dose:** 1.5 mL/kg IV bolus, then 0.25 mL/kg/min CRI for 30–60 min; repeat once if signs persist.
- **Also known as:** macrocyclic lactone, MDR1 breeds

Clinical signs: Mydriasis, apparent blindness; Ataxia, hypersalivation; Depression → coma; Tremors, bradycardia.

- Supportive nursing — recovery can take days
- Recumbent care: turning, eye lube, bladder management
- Avoid further P-gp substrate drugs

## Zinc phosphide (rodenticide)

- **Species:** dogs, cats and cattle
- **Typical source:** Grain-based rodent baits — releases phosphine gas in the acidic stomach
- **Urgency:** Critical — treat immediately
- **Antidote:** No specific antidote — supportive care
- **Also known as:** phosphine, rat cake

Clinical signs: Vomiting (garlic/rotten-fish odor); Abdominal pain, bloat; Dyspnea, pulmonary edema; Seizures, shock, hepatic failure.

- VENTILATE — vomitus off-gasses phosphine (protect staff, treat outdoors/windows open)
- Antacid (aluminium hydroxide) to slow gas release
- Gastric lavage with 5% sodium bicarbonate
- IV fluids + aggressive supportive care

## Oleander / cardiac glycoside plants

- **Species:** cattle, goats, sheep, horses and dogs
- **Typical source:** Garden clippings fed to livestock, browsing ornamental hedges
- **Urgency:** Critical — treat immediately
- **Antidote:** Digoxin-specific Fab fragments (rarely available in field)
- **Also known as:** kaner, nerium

Clinical signs: Vomiting/colic, bloody diarrhea; Bradycardia or tachyarrhythmias, AV block; Weakness, cold extremities; Sudden death.

- Activated charcoal 1–4 g/kg, repeat q6–8h
- Rumenotomy in valuable ruminants with large ingestion
- Atropine for bradyarrhythmia; lidocaine for ventricular tachyarrhythmia (dogs)
- Avoid calcium-containing fluids

## Lantana camara poisoning

- **Species:** cattle, goats and sheep
- **Typical source:** Browsing lantana scrub during fodder scarcity
- **Urgency:** Moderate
- **Antidote:** No specific antidote — supportive care

Clinical signs: Photosensitization — swollen, peeling muzzle/udder skin; Icterus; Anorexia, ruminal stasis, constipation; Dark urine.

- Remove from source + shade housing (UV avoidance)
- Activated charcoal 2 g/kg reduces hepatotoxin absorption early
- IV fluids + rumen transfaunation
- Treat secondary skin infection

## Lead poisoning

- **Species:** cattle, dogs and birds
- **Typical source:** Discarded batteries, old paint, sump oil — calves are notorious
- **Urgency:** Urgent
- **Antidote:** Calcium disodium EDTA
- **Antidote dose:** 75 mg/kg/day slow IV divided BID–TID × 3–5 days; repeat after 2-day rest if needed. Add thiamine 2–4 mg/kg IM (cattle).
- **Also known as:** battery, paint

Clinical signs: CNS: blindness, head pressing, circling; Bellowing, convulsions (cattle); GI: colic, anorexia; Chronic: weight loss, anemia with basophilic stippling.

- Remove source from paddock
- Magnesium sulfate PO precipitates lead in gut
- Seizure control with diazepam/barbiturate
- Food-safety: treated livestock carry residue — advise on withholding

## Ethylene glycol (antifreeze/coolant)

- **Species:** dogs and cats
- **Typical source:** Radiator coolant puddles — sweet taste attracts dogs and cats
- **Urgency:** Critical — treat immediately
- **Antidote:** Ethanol 20% (or fomepizole where available)
- **Antidote dose:** Ethanol 20%: dogs 5.5 mL/kg IV q4h × 5 then q6h × 4; cats 5 mL/kg q6h × 5 then q8h × 4. Must start <8–12 h post-ingestion.

Clinical signs: Stage 1 (0–12 h): "drunken" ataxia, PU/PD, vomiting; Stage 2 (12–24 h): apparent recovery, tachypnea; Stage 3 (24–72 h): oliguric renal failure, oral ulcers; Calcium oxalate crystalluria.

- Time-critical — treat on suspicion
- IV fluid diuresis + bicarbonate for acidosis
- Once anuric, only dialysis helps — grave prognosis

## Permethrin toxicosis (cats)

- **Species:** cats
- **Typical source:** Canine spot-on flea products applied to cats or close contact with treated dogs
- **Urgency:** Critical — treat immediately
- **Antidote:** No specific antidote — supportive care
- **Also known as:** pyrethroid, dog spot-on applied to cat

Clinical signs: Severe muscle tremors, twitching; Hyperesthesia, ear flicking; Seizures; Hyperthermia from tremor.

- Methocarbamol 55–220 mg/kg IV to effect — drug of choice for tremors
- Bathe with lukewarm water + dish soap once stable (NOT hot/cold)
- IV lipid emulsion 20% (1.5 mL/kg bolus then CRI) speeds recovery
- Treat hyperthermia; good prognosis with 24–72 h support

## Aflatoxicosis (moldy feed)

- **Species:** cattle, dogs, birds and pigs
- **Typical source:** Moldy maize/groundnut cake, poorly stored monsoon feed
- **Urgency:** Moderate
- **Antidote:** No specific antidote — supportive care

Clinical signs: Chronic: ill-thrift, drop in yield, rough coat; Icterus, hepatomegaly; Acute high dose: hemorrhage, hepatic encephalopathy; Milk residue risk (M1) in dairy animals.

- Replace the entire suspect feed lot
- Hepatoprotectants: SAMe, silymarin; vitamin K1 if bleeding
- High-quality protein diet during recovery
- Advise milk testing / withholding for dairy herds

## Note

> **Caution:** An assist for emergency triage, not a substitute for a poison-control consultation where one is available. Doses must be checked against the patient and the product.

## Frequently asked questions

### What is the antidote for organophosphate / carbamate insecticides poisoning?

Atropine sulfate. 0.2–0.5 mg/kg — ¼ IV, remainder SC/IM; repeat to effect (dry secretions). Add pralidoxime (2-PAM) 20 mg/kg slow IV for OPs if available. Alongside it: wash off dermal exposure with soap + water; do not atropinize to fixed dose — titrate to secretions.

### What is the antidote for anticoagulant rodenticide poisoning?

Vitamin K1 (phytomenadione). 2.5–5 mg/kg/day PO with fatty food, 2–4 weeks (second-generation agents need the full 4 wk); check PT 48 h after stopping. Alongside it: emesis if <2–4 h since ingestion; activated charcoal 1–4 g/kg.

### What is the antidote for urea / npn toxicity (ammonia poisoning) poisoning?

Cold water + weak acid (vinegar) orally. 2–6 L of 5% acetic acid (vinegar) + 20–40 L cold water per adult cow via stomach tube; repeat as rumen pH rebounds. Alongside it: rumenotomy and rumen lavage in valuable animals; iv isotonic saline + calcium borogluconate for tremors.

### What is the antidote for nitrate / nitrite poisoning poisoning?

Methylene blue. 1–2% solution at 4–15 mg/kg slow IV; repeat in 20–30 min if needed (ruminants tolerate repeat dosing). Alongside it: minimize stress/handling during crisis; remove suspect fodder from the whole herd.

### What is the antidote for snake envenomation (viperine) poisoning?

Polyvalent anti-snake venom (ASV). Species-appropriate polyvalent ASV IV per manufacturer; dose to venom load (not body weight) — pretreat for anaphylaxis risk. Alongside it: immobilize patient, keep bite below heart level; no tourniquets, incision, or suction.

## Sources

- Merck Veterinary Manual, 11th edition — Toxicology
- Plumb's Veterinary Drug Handbook

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