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Difficulty: HardPharmacological Therapies

An older adult client with a history of dysphagia and seizures receives scheduled medications via a percutaneous endoscopic gastrostomy (PEG) tube. The healthcare provider prescribes valproic acid syrup at a dosage of 15 mg/kg/day15\text{ mg/kg/day} divided into two equal doses. The client's current weight is 143 lb143\text{ lb}. The pharmacy supplies valproic acid syrup with a concentration of 250 mg/5 mL250\text{ mg}/5\text{ mL}.

How many mL\text{mL} should the practical nurse administer for one single dose? (Record the answer to the nearest tenth. Do not include units in your answer.)

Answer: 9.8 mL

Answer

9.8
The correct calculation requires sequential mathematical steps: converting weight to kilograms (143÷2.2=65 kg143 \div 2.2 = 65\text{ kg}), determining the total daily dose (65×15=975 mg65 \times 15 = 975\text{ mg}), dividing by two for a single dose (975÷2=487.5 mg975 \div 2 = 487.5\text{ mg}), calculating the required liquid volume (487.5×5250=9.75 mL487.5 \times \frac{5}{250} = 9.75\text{ mL}), and correctly rounding 9.759.75 to the nearest tenth to yield 9.89.8.

Step-by-Step Solution

1
Convert the client's weight from pounds (lb) to kilograms (kg).
143 lb÷2.2 lb/kg=65 kg143\text{ lb} \div 2.2\text{ lb/kg} = 65\text{ kg}
Weight-based medication dosages require the client's weight to be in kilograms.
2
Calculate the total daily dose in milligrams (mg).
65 kg×15 mg/kg/day=975 mg/day65\text{ kg} \times 15\text{ mg/kg/day} = 975\text{ mg/day}
The prescription specifies 15 mg15\text{ mg} per kilogram for the entire 24-hour period.
3
Calculate the amount for a single dose.
975 mg/day÷2 doses=487.5 mg/dose975\text{ mg/day} \div 2\text{ doses} = 487.5\text{ mg/dose}
The total daily amount must be divided into two equal doses as prescribed.
4
Calculate the volume (mL) to administer based on the pharmacy concentration.
487.5 mg250 mg×5 mL=1.95×5 mL=9.75 mL\frac{487.5\text{ mg}}{250\text{ mg}} \times 5\text{ mL} = 1.95 \times 5\text{ mL} = 9.75\text{ mL}
Dimensional analysis is used to convert the ordered dose in milligrams to the deliverable volume in milliliters.
5
Round the final answer to the nearest tenth.
9.75 mL→9.8 mL9.75\text{ mL} \rightarrow 9.8\text{ mL}
The question explicitly asks to record the answer to the nearest tenth. Because the hundredths digit is 5, round up.

Key Concept

Weight-based dosage calculation, unit conversion, and liquid medication administration via enteral tube.
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Topics

Pharmacological Therapies

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