Hi,
Ideally, you should take an opinion from nearest GP before starting the medicine. If you are not able to access one, you can as well give the medicine at the rate of 40mg/kg body weight i.e. it comes to around 400mg 8th hourly. You can give 3/4 of the tab once in 8 hours which is a safe dosage. But I still recommend you to go for the house hold remedy, encourage him to drink plenty of warm water, warm salt water gargles. Also you can give pain killers (such as Acetaminophen) if any. See a doctor at the earliest.
Regards
OHNS2010
i'm pretty sure that's way too much for her size. have u tried everything else? gargling w/ salty warm water, throat drops? sprays? spoon full of honey?