The doctor wants to give a dose of amoxicillin 200 mg bid to a 4 year old female. you have amoxicillin 250 mg/5 ml in 100 ml bottles. what would the dose be in ml?

To compute for the volume, we must multiply the desired dose (200 mg) of the drug to the reciprocal of the concentration of the preparation (200 mg/5mL).

The computation is as follows:




Therefore the dose of Amoxicillin in this case is 4 mL twice a day or BID. 

Amoxicillin is an antibiotic from the penicillin family. Patients that have been prescribed amoxicillin should respect the dosage:
In this case, we have 100ml of amoxicillin in a concentration of 250mg/5ml, and the patient needs 200mg her treatment, so you should do a cross multiplication:
250mg ==> 5ml
200mg ==> x
X = 200*5 / 250 = 4ml