I looked it up and it says 5 to 10 milligrams per pound 12 to 24 hours so I'm guessing it's 5 mg per pound every 12 hours or 10 mg per pound every 24 hours. But either way it goes by weight not age.
how much does your kitten weigh? was this prescription not given by a Vet? I am not sure you should be giving a young kitten such a strong antibiotic...yes it is 5mg per lb....but does the kitten even weight a full pound? I doubt it at 12 weeks old.
this is a systemic penicillin and has potential to produce serious even fatal allergic reactions...please consult a Vet before giving any medications to a cat esp a kitten..
i have a 3 month old cat who weight about 2 and a half pounds so unless the cat is way underweight they will be more than a pound. in fact if they weight under 1.5lbs they are underweight