Hydroxychloroquine has a narrow therapeutic range. Toxicity can occur when intake exceeds this range, especially with significant overdoses.
Clinical features of acute toxicity:
(1) acute cardiovascular toxicity, with cardiac dysrhythmias (widened QRS interval, ventricular tachycardia, atrioventricular block, sodium and potassium channel blockade)
(2) hypotension with cardiovascular collapse
(3) hypoxia
(4) seizures
(5) delirium
(6) hallucinations
(7) ataxia
(8) nausea and vomiting
(9) diarrhea
Laboratory findings:
(1) hypokalemia
(2) hypoglycemia
(3) thrombocytopenia
(4) abnormal liver function tests (toxic hepatitis)
(5) hemolytic anemia in G6PD deficient patients
Complications:
(1) nephropathy
(2) myopathy
(3) retinopathy
(4) vestibulopathy
(5) cardiomyopathy
(6) agranulocytosis
