Selphos poisoning

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Selphos aluminium phosphide poisoning management treatment 2024

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Selphos (Aluminium Phosphide) Poisoning

Selphos is one of several trade names for aluminium phosphide (AlP) tablets - others include Celphos, Alphos, Phostoxin, and Fumigran. It is infamous as "the agent of sure death" due to its extremely high mortality rate and the absence of a specific antidote.

Formulation

Gray-green tablets, each weighing 3 g, containing 56% active ingredient mixed with urea and ammonium carbonate
Each tablet liberates 1 g of phosphine gas (PH3)
Primarily used as a grain fumigant to destroy insects and rodents in stored grain

Mechanism of Toxicity

On contact with moisture (atmospheric humidity or gastric acid):

AlP + 3H2O → Al(OH)3 + PH3 (phosphine gas)

Phosphine is the actual toxic agent. It causes:

Mitochondrial dysfunction - inhibits cytochrome c oxidase (complex IV), blocking cellular respiration
Oxidative stress - generates reactive oxygen species, lipid peroxidation
Inhibits multiple enzyme systems including catalase and cholinesterase
Results in multi-organ failure: cardiovascular collapse is the principal cause of death

Fatal Dose and Period

Parameter	Value
Fatal dose	4-5 g (1-3 tablets)
Fatal period	12-36 hours

Signs and Symptoms

Gastrointestinal (early):

Nausea, vomiting, burning epigastric pain
Intense thirst and diarrhoea
Garlicky/fishy odour from breath (characteristic)

Cardiovascular:

Hypotension and shock
ECG abnormalities: sinus tachycardia, bradycardia, heart block
Arrhythmias
Myocardial damage, pericarditis, congestive cardiac failure

Respiratory:

Tightness in chest, dyspnoea
Severe pulmonary oedema (from inhaled phosphine)
Respiratory distress in terminal stages

Neurological/Metabolic:

Excitement and agitation (early)
Hypocalcaemia, tetany, convulsions, coma
Oliguria
Metabolic acidosis
Cold clammy skin

Terminal event: Death from cardiac failure

P C Dikshit Textbook of Forensic Medicine and Toxicology, p. 573-574
Parikh's Textbook of Medical Jurisprudence Forensic Medicine and Toxicology, p. 679

Diagnosis

Clinical:

History of ingestion / exposure
Characteristic garlicky odour

Chemical test (bedside):

Ask the patient to breathe on filter paper impregnated with 0.1 N silver nitrate for 5-10 minutes
Paper turns black if phosphine is present (silver nitrate is reduced to metallic silver)

Lab:

Serial blood phosphine levels
ABG (metabolic acidosis), serum electrolytes, ECG monitoring
Serum magnesium, calcium
Cardiac enzymes (myocardial damage)
NT-proBNP (predictive biomarker for mortality)

Management

There is NO specific antidote.

Immediate / Decontamination

Remove patient from source of exposure
Wash skin with soap and water (AlP can absorb through skin)
Healthcare workers must use full-face masks and gloves - do NOT perform mouth-to-mouth; phosphine off-gassing from vomit is hazardous
Gastric lavage with 3-5% sodium bicarbonate, 1% copper sulphate, 1% potassium permanganate, or mineral/coconut oil - these convert AlP to phosphate within 30 minutes
- Note: Some recent evidence questions routine gastric lavage since moisture contact during the procedure may accelerate phosphine generation
Oil-based decontamination (coconut oil) has shown benefit in some studies; a 2024 systematic review and meta-analysis supports oil-based gastric lavage

Supportive Treatment

Problem	Intervention
Arrhythmias	Magnesium sulphate 3 g IV bolus, then 6 g infusion over 24 h for 5-7 days
Hypocalcaemia/tetany	Intravenous calcium salts
Metabolic acidosis	Sodium bicarbonate 50 mEq q15 min until arterial HCO3 > 15 mmol/L
Hypotension	IV fluids (0.9% NaCl bolus); low-dose dopamine infusion
Pulmonary oedema	Corticosteroids; oxygen; positive pressure ventilation/intubation
Bronchospasm	Aerosol bronchodilators
Infection	Antibiotics
Oxidative stress	Antioxidants (N-acetylcysteine, glutathione, Vitamin E) - used adjunctively

Emerging/Investigated Therapies

Intravenous lipid emulsion (ILE) - shown benefit in case reports and a 2024 RCT (acts as lipid sink for lipophilic phosphine)
Glucose-insulin-potassium (GIK) infusion - pilot RCT showed some benefit for myocardial support
High-dose insulin therapy - under study (RCT published 2024)
Hyperbaric oxygen therapy - rare successful cases reported; limited evidence
Monitoring for 72 hours minimum; continuous cardiac monitoring mandatory

Medicolegal Aspects

Common method of suicide in rural India, especially in Haryana, Punjab, Uttar Pradesh, and Rajasthan
Used in dowry deaths (homicidal poisoning) in rural India - only a fragment of a tablet is sufficient
The resemblance of tablets to medicinal preparations makes accidental ingestion possible
Autopsy findings include congestion of all organs and frothy fluid in airways

Key Points to Remember

Phosphine is the actual toxin, not AlP itself
Garlicky/fishy breath odour is the clinical hallmark
No antidote exists - all treatment is supportive
Cardiac failure (cardiogenic shock) is the primary cause of death
Magnesium sulphate is the cornerstone drug for arrhythmias
Coconut/mineral oil lavage may reduce phosphine liberation in the stomach
High mortality even with aggressive ICU care

Recent evidence note: A 2025 review (PMID 41523401) specifically addresses neurological manifestations of AlP poisoning, an underappreciated aspect. A 2024 systematic review supports oil-based gastric decontamination. High-dose insulin and ILE are being studied in RCTs as adjuncts.

Harrison based

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Selphos (Aluminium Phosphide) Poisoning - Harrison's 22E Perspective

Important clarification upfront

Harrison's Principles of Internal Medicine 22E does not have a dedicated section on aluminium phosphide / Selphos poisoning. The toxicology chapter (Chapter 470, "Poisoning and Drug Overdose") explicitly states that "Poisonings not covered in this chapter are discussed in specialized texts." AlP poisoning is not among its covered syndromes - it focuses on poisonings common in a Western context (acetaminophen, opioids, alcohol, carbon monoxide, etc.).

What Harrison's does provide is the general framework for managing any poisoning, which directly applies to Selphos. Here is how that framework maps onto AlP poisoning:

Harrison's General Framework Applied to Selphos Poisoning

1. Treatment Goals (Harrison's Table 470-3)

Harrison's defines five universal goals:

Goal	Application to Selphos
Support vital signs	Maintain BP, treat arrhythmias, ventilate
Prevent further absorption	GI decontamination (oil/bicarbonate lavage)
Enhance elimination	Supportive; no established extracorporeal method
Administer antidotes	None exist for AlP
Prevent re-exposure	Psychiatric referral (suicidal ingestion), regulatory notification

2. Supportive Care (Harrison's priority)

Harrison's emphasises this is the backbone of all poisoning management:

Airway protection - early intubation if respiratory distress or pulmonary oedema develops
Oxygenation/ventilation - oxygen for hypoxia; positive pressure ventilation for pulmonary oedema
Treatment of arrhythmias - magnesium sulphate is the agent of choice (IV 3 g bolus, then infusion)
Haemodynamic support - IV fluids, vasopressors (dopamine/noradrenaline) for refractory shock
Correction of metabolic derangements - sodium bicarbonate for metabolic acidosis; calcium for hypocalcaemia
Treatment of seizures - benzodiazepines
Prevention of secondary complications - ICU monitoring, treat infections

3. GI Decontamination (Harrison's principles)

Harrison's states decontamination should be selective, not routine, based on:

Time since ingestion (efficacy drops sharply after 1 hour)
Severity of expected toxicity
Risk of complications

For AlP specifically:

Activated charcoal - Harrison's preferred decontamination method generally, but its efficacy for AlP is uncertain (AlP is an inorganic compound; Harrison's notes that "charged chemicals and inorganic compounds are not well adsorbed by charcoal")
Gastric lavage - Harrison's reserves this for "life-threatening poisons not treatable by other means" - AlP qualifies. However, a unique concern with AlP is that adding moisture during lavage accelerates phosphine liberation; oil-based lavage (coconut oil/liquid paraffin) is preferred over water to avoid this
Skin decontamination - wash with soap and water (AlP is dermally absorbed)

4. Enhancement of Elimination

Harrison's lists: multiple-dose activated charcoal, urinary pH alteration, haemodialysis, haemoperfusion, CVVH, hyperbaric oxygen.

For AlP:

No extracorporeal method has proven effective for eliminating phosphine
Hyperbaric oxygen - listed by Harrison's as a modality; isolated case reports suggest benefit in AlP, though evidence remains very limited
Haemoperfusion/CVVH may assist multi-organ support, not phosphine elimination per se

5. Antidotes

Harrison's framework: "Neutralization by antibodies, chemical binding, metabolic antagonism, physiologic antagonism."

For AlP: No specific antidote exists. This is what makes Selphos poisoning so lethal. Agents used empirically include:

Magnesium sulphate (physiologic antagonism for arrhythmias)
N-acetylcysteine, glutathione (antioxidants - metabolic support)
Intravenous lipid emulsion (ILE) - emerging evidence; acts as a lipid sink
Glucose-insulin-potassium (GIK) - myocardial support
Sodium bicarbonate - metabolic antagonism of acidosis

6. Harrison's Global Considerations Note

Harrison's 22E (2025) specifically adds a Global Considerations note acknowledging that poisoning patterns differ globally - immigrants, travelers, and internet purchasing introduce agents uncommon in Western settings. AlP is a perfect example: it is the leading cause of pesticide suicide in South Asia and the Middle East but rarely encountered in North America/Europe.

Bottom Line

Harrison's does not address Selphos directly. For this topic, forensic medicine and toxicology texts (P.C. Dikshit, Parikh's) and emergency medicine references (Rosen's) are the authoritative sources. Harrison's framework for general poisoning management remains applicable and is consistent with what those texts recommend for AlP.

Harrison's Principles of Internal Medicine 22E, Chapter 470: Poisoning and Drug Overdose, pp. 3749-3758

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