Dosage Calculations 1

Question 1

You are caring for a patient at home who must take magnesium hydroxide/aluminum hydroxide (Maalox) 30 mL PO. How will you instruct the patient to measure the dose using ordinary household measuring devices? Fill in the blanks. Record your answer to the nearest whole number.

Answer 1

2 tbsp

One tablespoon is equal to 15 mL.
Convert 30 mL to tablespoons by multiplying it by one tablespoon.
Then, divide 30 by 15 mL to get the final answer of 2 tbsp.

Question 2

The physician orders alprazolam (Xanax) 0.5 mg PO. You have on hand Xanax 0.25 mg tablets. How many tablet(s) will you give? Fill in the blanks.

Answer 2

2 tablets

Multiply 0.5 mg to 1 tablet (vehicle) to get 0.5 mg.
Then divide 0.5 mg with 0.25 units (drug on hand) to get 2 tablets.

Question 3

You need to administer 250 mg of erythromycin (Erythrocin) PO. You have on hand 0.5 g tablets. How many tablet(s) will you give? Fill in the blanks

Answer 3

0.5 Tablets

1 g is equal to 1000 mg.
Convert 250 mg to grams first by multiplying 250 mg to 1 g, then divide the answer by 1000 mg to get 0.25 g.
Then use the standard formula above.
Multiply 0.25 g (desired dose) to 1 tablet (vehicle) to get 0.25 g.
Finally, divide 0.25 g by 0.5 g (drug on hand) to get 0.5 g or ½ tablet.

Question 4

You have available lorazepam (Ativan) 0.5 mg tablets, and you need to administer 1 mg PO. How many tablet(s) will you administer? Fill in the blanks.

Answer 4

2 Tablets

Multiply 1 mg (desired dose) to 1 tablet (vehicle) to get 1 mg.
Then, divide 1 mg by 0.5 mg (drug on hand) to get 2 tablets.

Question 5

A patient with heart failure has a daily order for digoxin (Lanoxin) 0.25 mg PO. Digoxin 0.125 mg tablets are available. How many tablet(s) should you give? Fill in the blanks.

Answer 5

2 Tablets

Multiply 0.25 mg (desired dose) to 1 tablet (vehicle) to get 0.25 mg.
Divide 0.25 mg by 0.125 mg (drug on hand) to get 2 tablets.

Question 6

Your patient needs 2,000 mL of saline IV over 4 hours for severely deficient fluid volume. How many milliliters per hour will you set on a controller?

Answer 6

500 mL/hr

Divide 2000 mL (total volume) with 4 hours (number of hours to run) to get 500mL/hour.