Chloroquine poisoning: ventricular fibrillation following 'trivial' overdose in a child

Chloroquine for SARS-CoV-2: Implications of Its Unique Pharmacokinetic and Safety Properties

Since in vitro studies and a preliminary clinical report suggested the efficacy of chloroquine for COVID-19-associated pneumonia, there is increasing interest in this old antimalarial drug. In this article, we discuss the pharmacokinetics and safety of chloroquine that should be considered in light of use in SARS-CoV-2 infections. Chloroquine is well absorbed and distributes extensively resulting in a large volume of distribution with an apparent and terminal half-life of 1.6 days and 2 weeks, respectively. Chloroquine is metabolized by cytochrome P450 and renal clearance is responsible for one third of total clearance. The lack of reliable information on target concentrations or doses for COVID-19 implies that for both adults and children, doses that proved effective and safe in malaria should be considered, such as 'loading doses' in adults (30 mg/kg over 48 h) and children (70 mg/kg over 5 days), which reported good tolerability. Here, plasma concentrations were < 2.5 μmol/L, which is associated with (minor) toxicity. While the influence of renal dysfunction, critical illness, or obesity seems small, in critically ill patients, reduced absorption may be anticipated. Clinical experience has shown that chloroquine has a narrow safety margin, as three times the adult therapeutic dosage for malaria can be lethal when given as a single dose. Although infrequent, poisoning in children is extremely dangerous where one to two tablets can potentially be fatal. In conclusion, the pharmacokinetic and safety properties of chloroquine suggest that chloroquine can be used safely for an acute virus infection, under corrected QT monitoring, but also that the safety margin is small, particularly in children.

Are 1–2 dangerous? Chloroquine and hydroxychloroquine exposure in toddlers

Ingestion of 1-2 tablets of chloroquine or hydroxylchloroquine is thought to predispose children under 6 years of age to serious morbidity and mortality. The actual risk to the toddler and appropriate guidelines for care remain unclear at a time when both medications are therapeutically utilized as anti-inflammatory agents in addition to their main use as anti-parasitics. A review of the literature and data from the American Association of Poison Control Centers reveals instances where exposure to as little as 1-2 tablets of chloroquine resulted in serious consequences. Based on these findings, ingestions of greater than 10 mg/kg of chloroquine base or unknown amounts require triage to the nearest health care facility for 4-6 h of observation. There is very limited data on pediatric hydroxychloroquine overdoses and no reports of toxicity from 1-2 pills, but given its similarity to chloroquine, it also should be considered potentially toxic at small doses. Thus, similar recommendations should be followed for triage after accidental hydroxychloroquine overdose.

Treatment of hydroxychloroquine overdose

Hydroxychloroquine overdoses are rarely reported with 7 previous cases found in the English medical literature. We report a case and review the literature. A 16-year-old girl ingested a handful of hydroxychloroquine 200mg, 30 minutes before presentation and presented with tachycardia (heart rate 110 beats/min), hypotension (systolic blood pressure 63 mm Hg), central nervous system depression, conduction defects (QRS = 0.14 msec), and hypokalemia (K = 2.1 meq/L). She was treated with fluid boluses and dopamine, oxygen, and potassium supplementation. Toxicologic tests confirmed the presence of hydroxychloroquine. The patient's hypotension resolved within 4.5 hours, serum potassium stabilized in 24 hours, and tachycardia gradually decreased over 3 days. Although hydroxychloroquine overdoses are very rare, life-threatening hypotension, conduction problems, and hypokalemia can occur within 30 minutes of ingestion. Symptoms are similar to chloroquine and treatment must be implemented quickly and should be modeled after experience with chloroquine overdoses. Treatment modalities need further study, but current recommendations are: (1) diazepam for seizures and sedation; (2) early intubation and mechanical ventilation; (3) epinephrine for treatment of vasodilation and myocardial depression; (4) potassium replacement with close monitoring of levels; (5) charcoal for gastrointestinal decontamination if ingestion occurred within an hour; (6) high dose diazepam for life-threatening symptoms, until more information becomes available. No value was found for serum alkalinization or extracorporeal methods of drug removal.

Disturbances of potassium homeostasis in poisoning

Unless renal function is impaired or rhabdomyolysis is severe, hyperkalemia is a relatively uncommon metabolic complication of poisoning. In contrast, marked hypokalemia is a more common problem and may have serious sequelae. Most potassium disturbances in acute poisoning are due to disruption of extra-renal control mechanisms, notably the activity of Na+/K+ ATPase and K+ channels. Hypokalemia occurs because of increased Na+/K+ ATPase activity (e.g. beta 2 agonist, theophylline or insulin poisoning), competitive blockade of K+ channels (e.g. barium or chloroquine poisoning), gastrointestinal losses and/or alkalosis. Hyperkalemia follows inhibition of Na+/K+ ATPase activity (e.g. by digoxin), increased uptake of potassium salts, disruption of intermediary metabolism (e.g. cyanide poisoning), activation of K+ channels (e.g. fluoride poisoning), and the presence of acidosis and rhabdomyolysis, particularly if the latter is complicated by renal failure. Hypokalemia results in generalized muscle weakness, paralytic ileus, ECG changes (flat or inverted T waves, prominent U waves, ST segment depression) and cardiac arrhythmias (atrial tachycardia +/- block, AV dissociation, VT, VF). Hyperkalemia is associated with abdominal pain, diarrhea, muscle pain and weakness, ECG changes (tall peaked T waves, ST segment depression, prolonged PR interval, QRS prolongation) and cardiac arrhythmias (VT, VF). Significant disturbances of potassium homeostasis are often unrecognized and may cause considerable morbidity and mortality. Prompt recognition and appropriate treatment of these disturbances could be life-saving.

The hazards of chloroquine self prescription in west Africa

We report a severe accidental chloroquine poisoning in a West African adult. This intoxication results from the widespread practice in Senegal of taking mild doses of chloroquine for a few days (i.e. 300 mg x 3 for 3 or 5 days) following the onset of any fever suspected of being a malaria attack. To our knowledge, this practice and this kind of poisoning have not been reported before. The present clinical case demonstrated that self-medication can be the cause of severe chloroquine poisoning responsible for arrhythmia (torsades de pointes). In this clinical case, no diazepam was administered. However, there were no further problems and the patient was discharged three days after admission to the intensive care unit.