Question

How many ml of non medicated, flavored syrup base must be added to 1 pint of ranitidine syrup, 15 mg/ml, to change its concentration to 5 mg/ml?

Answer 1

1 pint = 473 ml

Each ml contains 15 mg of medicine.

Total mg of 1 pint ranitidine syrup = 473 ml $\times$ 15 mg

                                                      = 7,095 mg

To get 5 mg in 1 ml of syrup divide total dose with required dose = 7,095 $\div$ 5

                                                       = 1419 ml (total solution to be in the container with 5 mg/ml)

The syrup already contains 1 pint of ranitidine = 473 ml

We must deduct ranitidine syrup from the total solution = 1419 - 473

                                                                                        = 946

To change the concentration of 1-pint ranitidine syrup of 15 mg /ml to 5 mg /ml we must add 946 ml of non medicated flavoured syrup.