Phosphine gas is produced in poisoning with which rodenticides?

• A. Hydrogen
• B. Phosphine
• C. Methane
• D. Ammonia

Answer: (B)

Phosphine gas is produced when rodenticides containing metal phosphides, such as aluminum phosphide or zinc phosphide, come into contact with moisture or gastric acid. The reaction liberates phosphine (PH3): AlP + 3 HCl → PH3 + AlCl3 and Zn3P2 + 6 HCl → 3 ZnCl2 + 2 PH3. This gas is highly toxic because it disrupts mitochondrial respiration by inhibiting cytochrome c oxidase, causing cellular hypoxia, metabolic acidosis, and often rapid cardiovascular collapse and pulmonary edema. Clinically, patients may have gastrointestinal symptoms, dyspnea, hypotension, and sometimes a garlic-like odor (though odor is not reliable). There is no specific antidote; management is supportive, focusing on stabilization and treating shock and respiratory failure.