Ondansetron - what is the youngest age that should be allowed to take 8mg pill?

Little information is available about dosage in pediatric patients 4 years of age or younger
"For pediatric patients 4 through 11 years of age, the dosage is one 4 mg ondansetron orally disintegrating tablet given 3 times a day. The first dose should be administered 30 minutes before the start of emetogenic chemotherapy, with subsequent doses 4 and 8 hours after the first dose. One 4 mg ondansetron orally disintegrating tablet should be administered 3 times a day (every 8 hours) for 1 to 2 days after completion of chemotherapy."
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