Management of Rat Poison (Rodenticide) Poisoning

Classification of Common Rodenticides

1. Anticoagulant Rodenticides (Most Common)

Mechanism

Clinical Features

• Bleeding diathesis: hematuria, epistaxis, GI bleeding, oral mucosal bleeding, hemoptysis
• Symptoms are delayed 2-5 days after ingestion (time to deplete clotting factors)
• Severely elevated INR (mean INR ~15 in brodifacoum poisoning)
• Deaths from internal hemorrhage reported

Diagnosis

• Prothrombin time (PT) / INR - key test; check at 48 hours post-ingestion if agent withheld
• PTT, CBC (anemia, thrombocytopenia)
• Confirmatory: serum LAAR levels by HPLC (detects brodifacoum, difenacoum, bromadiolone)
• Chest/abdominal X-ray if hemorrhage suspected

Management

• Induce emesis (in animals; in humans - consider gastric lavage or activated charcoal only if early and clinician judgment supports it)
• Activated charcoal 1-2 g/kg PO as aqueous slurry, repeat q 4-8 hours without cathartic

• This is the TRUE antidote - only Vitamin K1 (phytonadione) is effective; Vitamin K3 (menadione) is NOT acceptable and can cause hemolysis
• Takes at least 6 hours after dosing to regenerate clotting factors
• Subcutaneous route: phytonadione 10-25 mg, repeat every 6-12 hours until oral therapy can start
• Oral dosing for warfarin poisoning: typically 2-4 weeks
• For LAARs (brodifacoum): median treatment duration 140 days, up to 730 days - due to fat solubility and high volume of distribution
• No consensus on exact dosing; titrate to PT/INR and bleeding symptoms
• Discontinue when PT/INR normalizes off treatment

• 4-factor prothrombin complex concentrate (4F-PCC) - first-line for major bleeding requiring rapid INR correction
• Fresh frozen plasma (FFP) - alternative if PCC unavailable
• IV Vitamin K1 (not IM - risk of hematoma; IV given slowly to avoid anaphylaxis)
• Packed red blood cells for significant anemia
• IV fluid resuscitation

• Serial PT/INR every 6-12 hours until stable
• Check PT 2-3 days after completing treatment to confirm success
• Monitor PCV and coagulation profile regularly during treatment
• Goldman-Cecil Medicine, Table 96-6 (Antidotes and Indications)
• Henry's Clinical Diagnosis and Management by Laboratory Methods (Brodifacoum/LAAR section)

2. Zinc Phosphide / Aluminum Phosphide

Mechanism

Clinical Features

• Onset within hours
• GI: nausea, vomiting, severe abdominal pain, diarrhea
• CNS: headache, dizziness, altered consciousness, seizures
• Cardiovascular: hypotension, arrhythmias, shock
• Pulmonary: pulmonary edema, ARDS
• Hepatic and renal failure
• Characteristic smell: garlic/fishy odor from phosphine gas

Management

• No specific antidote available
• Gastric lavage with potassium permanganate 1:10,000 or sodium bicarbonate (to alkalinize stomach and reduce phosphine liberation)
• Oral coconut oil or liquid paraffin to coat the stomach (reduce PH3 release)
• Avoid oils and fats orally in the acute phase - actually may increase absorption; use is debated
• Supportive care: IV fluids, vasopressors for shock, mechanical ventilation for respiratory failure
• Antioxidants being studied (N-acetylcysteine, magnesium sulfate, coconut oil)
• Treat metabolic acidosis, cardiac arrhythmias, seizures symptomatically
• Staff should take precautions (mask/ventilation) - exhaled phosphine is toxic to caregivers

3. Bromethalin (Neurotoxic Rodenticide)

Mechanism

Clinical Features

• Two forms: high dose - acute tremors, seizures, hyperthermia, death; low dose - ascending paralysis over days
• Onset: 4-36 hours after ingestion

Management

• No specific antidote
• Decontamination: emesis, activated charcoal (multiple doses)
• Treat cerebral edema: mannitol, dexamethasone
• Anticonvulsants for seizures
• Supportive intensive care

4. Cholecalciferol (Vitamin D3 Analogue)

Mechanism

Clinical Features

• Polyuria, polydipsia, vomiting, weakness
• Renal failure, cardiac arrhythmias, seizures

Management

• No direct antidote
• IV fluids (0.9% NaCl) - cornerstone; promotes calciuresis
• Furosemide (loop diuretic) - increases calcium excretion
• Calcitonin - lowers calcium rapidly
• Corticosteroids (prednisolone) - reduce intestinal calcium absorption, increase renal excretion
• Bisphosphonates (pamidronate) in severe cases
• Restrict dietary calcium and vitamin D
• Dialysis in severe refractory hypercalcemia with renal failure

5. Strychnine

Mechanism

Clinical Features

• Severe painful muscle spasms, opisthotonos, risus sardonicus
• Hyperthermia from muscular activity
• Rhabdomyolysis, renal failure
• Death from respiratory muscle failure

Management

• No specific antidote
• Benzodiazepines (diazepam, midazolam) - first-line for muscle rigidity and seizures
• Barbiturates or propofol infusion for refractory spasms
• Neuromuscular blockade + mechanical ventilation in severe cases
• Cool the patient (hyperthermia)
• Supportive care; minimize stimulation (dark, quiet room)

General Principles (All Rodenticides)

1. Identify the poison - read the label, call poison control (national hotlines available)
2. Decontamination within the first 1-4 hours: gastric lavage or activated charcoal if ingestion confirmed and airway protected
3. Stabilize the patient - airway, breathing, circulation first
4. Specific antidote where available (Vitamin K1 for anticoagulants)
5. ICU monitoring for severe cases
6. Poison control consultation strongly recommended

Recent literature note: A 2025 retrospective review (PMID: 40974629) of 88 anticoagulant rodenticide poisoning cases highlighted forensic implications and the importance of HPLC-based toxicological confirmation. A 2025 review on zinc phosphide toxicity (PMID: 41768810) discussed proposed therapeutic approaches including antioxidant therapies, though no definitive antidote has emerged.

Should This Case Be Registered as an MLC?

YES - This case MUST be registered as an MLC.

Reasons This IS an MLC

1. "Alleged" History of Fall

• Type, size, site, shape of injuries
• Whether the injuries are consistent with a fall from stairs (accidental), OR whether any injuries suggest assault/foul play
• Age of injuries (fresh vs. old)

2. Alcohol Intoxication

• Was the "fall" truly accidental, or was it a result of being assaulted while intoxicated?
• Was there an altercation?
• Could this be a case of foul play disguised as an accident?

3. Injury with Unconfirmed/Suspicious Circumstances

• Domestic violence / assault (especially if the patient is not giving history freely)
• Homicidal attempt made to look accidental
• Injury under influence that may have legal implications later

4. Potential for Grievous Hurt

What You Must Do as the Medical Officer

Key Principle to Remember

The decision to make a case an MLC rests solely with the attending Medical Officer - NOT with the patient or relatives. No one can pressure you to avoid registering it as an MLC. The word "alleged" in the history already signals that the circumstances are unconfirmed.

Regarding "PREMLC" / Police Report

• You do not wait for police to arrive before treating the patient
• Intimate police after initiating treatment
• Police intimation can be verbal (phone) initially, followed by written communication
• If the case is received from police (police case), acknowledge receipt and file accordingly
• If brought directly by public (private case), you are responsible for informing police