Dosage Calculations Pt.2 Pop Quiz

Diphenhydramine hydrochloride 25 mg orally every 6 hours, is prescribed for a child with an allergic reaction. The child weighs 25 kg. The safe pediatric dosage is 5 mg/kg/day. Which conclusion should the nurse infer?

• The dose is too low.
• The dose is too high.
• The dose is within the safe dosage range.
• There is not enough information to determine the safe dose.

Answer explanation

Use the formula for calculating a safe dosage range.
Safe dose parameter: 5 mg/kg/day × 25 kg = 125 mg/day
Dosage frequency: 25 mg × 4 doses (every 6 hours) = 100 mg/day
The dose is within the safe dosage range.

A pediatrician's prescription reads "ampicillin sodium 125 mg." The medication label reads that there are 1000 mg in 7.4 mL after reconstitution. The nurse prepares to draw up how many milliliters to administer 1 dose? (round to nearest tenths)

Answer explanation

Desired = 125mg
Available = 1000mg
Volume = 7.4

Use the 'Desired over Available' medication formula to calculate the correct dose: D/A x V

= 125mg/1000mg x 7.4mL = 0.925 ml (rounded to 0.9 ml)

The nurse has a prescription to infuse 1000 mL of 5% dextrose in lactated Ringer's solution at 80 mL per hour. The nurse time-tapes the intravenous (IV) bag with a start time of 0900. After making hourly marks on the time-tape, the nurse should note which completion time for the bag?

• 1530
• 1730
• 1930
• 2130

Answer explanation

At a rate of 80 mL/hr, the 1000-mL bag will be finished infusing in 12.5 hours. This brings the end time to 2130 using military time.

Convert the following: 1 cup = __ mL (enter numbers only)

Answer explanation

1 cup = 240mL

The primary health care provider prescribes 1000 mL of 0.45% NaCl to run over 8 hours. The drop (gtt) factor is 15 gtt/mL. The nurse plans to adjust the flow rate to how many gtt/min? Fill in the blank. Round your answer to the nearest whole number. (enter numbers only w/o units)

Answer explanation

The prescribed 1000 mL is to be infused over 8 hours. Follow the formula, and multiply 1000 mL by 15 (gtt factor). Then divide the result by 480 minutes (8 hours × 60 minutes). The infusion is to run at 31.2 or 31 gtt/min.

Total volume × Drop factor
–––––––––––––––––––––––––– = gtt/min
Time in minutes


1000 mL × 15 gtt
–––––––––––– = 31.2 gtt/min
480 minutes


= 31 gtt/min (rounded down)