Order for tylenol 3/4 tsp (120mg/5ml) is ordered. On hand is Tylenol 200mg/5ml. how many ml's will you give?

Question

Answer is 2.25mL.. how do you come up with it?

Answer 1

120/200 = .6, so .6 x 3/4 = .45
.45 tsp. You can look up conversion of this to ml

Answer 2

First find out how many mg of medicine you are administering

1 teaspoon = 5 ml

.75 (5 ml) (120 mg / 5ml) = 90 mg of Tylenol

since you want to give the same amount of medicine just at a different concentration then the new volume is:

90 mg of Tylenol (5 ml / 200 mg ) = 2.25 ml

remember to manipulate the given ratios so the units cancel.