EDIT: this source [0] seems to confirm that it is indeed milligrams, but I don't understand how any of this jives with what I found earlier from the FDA on therapeutic index and overdosing.

[0]: https://docs.google.com/document/d/e/2PACX-1vTi-g18ftNZUMRAj...

See the original comment with my findings from the FDA below, however.

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I don't think it's a mistake. 600mg per day is 14x the recommended dosage for malarial suppression with cholorquine.

Per the FDA, the dosage is 300mg of chloroquine per week for malarial suppression:

> Adult Dose: 500 mg (=300 mg base) on exactly the same day of each week.

For children:

> The weekly suppressive dosage is 5 mg calculated as base, per kg of body weight, but should not exceed the adult dose regardless of weight.

Source: https://www.accessdata.fda.gov/drugsatfda_docs/label/2013/00...

Additionally, it seems that it is incredibly easy to fatally overdose on this:

> Chloroquine is very rapidly and completely absorbed after ingestion. Toxic doses of chloroquine can be fatal. As little as 1 g may be fatal in children. Toxic symptoms can occur within minutes. These consist of headache, drowsiness, visual disturbances, nausea and vomiting, cardiovascular collapse, shock and convulsions followed by sudden and early respiratory and cardiac arrest. Hypokalemia has been observed with arrhythmias in cases of intoxication. The electrocardiogram may reveal atrial standstill, nodal rhythm, prolonged intraventricular conduction time, and progressive bradycardia leading to ventricular fibrillation and/or arrest. Cases of extrapyramidal disorders have also been reported in the context of chloroquine overdose (see WARNINGS and ADVERSE REACTIONS)

See also this paper about known cases of overdose in kids: https://pediatrics.aappublications.org/content/27/1/95.long?...

Note that is for all for cholorquine base, not chloroquine phosphate which is ~60% choloroquine.