Oral solution dosage calculation
There is a slight difference between oral solution dosage calculation and tablet dosage calculation.In oral solution, the weight of the drug is contained in a certain volume of solution.
Here is the difference:
Liquid or oral solution: 100 mg in 5 mL
Solid or tablets/capsules: 200 mg in 1 tablet
The dosage strength is still an important piece of information when doing calculation and this information can be found on the medication label.
Example #1:
Say the dosage strength is 250 mg per 5 mL and the bottle contains 2 FL Oz ( 2 fluid ounce) of oral solution. If the doctor orders 500 mg, how much oral solution will you give?
500 mg is twice as big as 250 mg, so the oral solution is also twice as big.
Since 500 mg = 250 × 2, the oral solution to give = 5 mL × 2 = 10 mL
You will give 10 mL of oral solution
Example #2:
Say the dosage strength is 50 mg per 2 mL and the bottle contains 3 FL Oz ( 2 fluid ounce) of oral solution . If the doctor orders 25 mg, how much oral solution will you give?
Since 25 mg =
50 mg
2
,the quantity to give should also be divided by 2
2 mL
2
= 1 mL
Therefore, give 1 mL of oral solution
Observation:
Quantity of liquid given in example #1 =
500 mg
250 mg
× 5 mL = 2 × 5 mL =10 mL
Quantity of liquid given in example #2 =
25 mg
50 mg
× 2 mL = 0.5 × 2 mL = 1 mL
You could try to keep in mind the above when doing calculation.
Example #3:
Say the dosage strength is 300 mg per 3 mL and the Bottle contains 3 Fl Oz of medication . If the doctor orders 0.6 g, how much liquid will you give?
Before you use the formula above, all units should be the same. Thus, convert 300 mg to g.
300 mg = 0.3 g
Quantity of liquid to give =
0.6 g
0.3 g
× 3 mL
Quantity of liquid to give =
6 g
3 g
× 3 mL = 2 × 3 mL = 6 mL