A 7 year old child is brought to the emergency with seizures and drowsiness. The child had been receiving some drugs for fever for the past two days. Child is found to be cyanosed with an oxygen saturation of 40% and unresponsive to oxygen therapy. Blood gas analysis reveals a normal PaO2. Which drug intake may have caused the above condition ?
Chloroquine Toxicity Mechanism
The child presents with severe cyanosis and hypoxia (Oxygen Saturation of 40%) that is unresponsive to oxygen therapy, alongside a normal arterial oxygen partial pressure (PaO2). This clinical picture is characteristic of methemoglobinemia.
Methemoglobinemia Explained
- Methemoglobinemia occurs when the iron in hemoglobin is oxidized from the ferrous (Fe2+) state to the ferric (Fe3+) state.
- This ferric iron cannot bind oxygen, impairing oxygen transport from the lungs to the tissues, despite adequate oxygen levels in the blood (normal PaO2).
- The cyanosis and symptoms like seizures and drowsiness result from severe tissue hypoxia. Oxygen therapy is ineffective because the problem lies with the hemoglobin's ability to carry oxygen, not the oxygen supply in the lungs.
Drug-Induced Methemoglobinemia
Several drugs can induce methemoglobinemia. Among the options provided:
- Chloroquine is known to sometimes cause methemoglobinemia as a side effect.
- Amoxycillin-Clavulanic acid is an antibiotic.
- Paracetamol (Acetaminophen) overdose primarily causes liver toxicity.
- Mefenamic acid is a non-steroidal anti-inflammatory drug (NSAID).
Given the specific symptoms, particularly the normal PaO2 with severe cyanosis unresponsive to oxygen, Chloroquine is the most likely causative agent among the choices, leading to methemoglobinemia.
Important Questions from Drug Overdose
- A 22-year-old lady presented with complaint of chronic daily headache. She has prior history of migraine but increasingly unrelieved with analgesics. She has history of using Sumatriptan almost daily since the last three weeks. What is the most likely diagnosis?
Consider the following statements regarding paracetamol toxicity :
1. Toxicity is caused by an intermediate reactive metabolite that binds covalently to cellular proteins causing cell death.
2. Antidotes for paracetamol act by replenishing hepatic glutathione and should be administered to all patients with acute poisoning.
3. Intravenous acetyl cysteine is a highly efficacious antidote if administered within 8 hours of the overdose.
4. Methionine may be used as an alternative antidote but it is less effective than acetyl cysteine.
Which of the statements given above are correct?
- Which one of the following is a specific antidote for opiate overdose ?
- Which one of the following is the most appropriate treatment of overdose of aspirin ingestion ?
