A drug is prescribed 200 mg dose every 8 hours (q8h).as 2–20 mg/kg/day in ideal dose. A patient weighs 50 Lbs. What is the average dose per administration?

Appeared in: NORCET 10 Prelims-2026

Explanation

The first step is to convert the patient's weight from pounds (lbs) to kilograms (kg) by dividing by 2.2, which yields 22.73 kg.
Next, calculate the total safe daily dose range using the patient's weight in kg. The minimum is 2 mg/kg/day (45.46 mg/day) and the maximum is 20 mg/kg/day (454.6 mg/day).
The prescription is for every 8 hours (q8h), which means the drug is administered 3 times in a 24-hour period.
To find the safe range per administration, divide the daily dose range by 3. This gives a single-dose range of 15.15 mg to 151.53 mg.
Comparing this calculated range to the options, 20-200 mg is the only range that reasonably encompasses the safe dose per administration.

Option A: This range is significantly higher than the calculated safe dose range per administration (15.15–151.53 mg).
Option B: This range (40-460 mg) closely represents the total daily safe dose range (45.46–454.6 mg/day), not the dose per administration as requested in the question.
Option C: This range is also incorrect and does not align with the calculated safe dose per administration.

Visual 1: Flowchart: 'Steps for Safe Drug Dosage Calculation'. This visual would outline the process: 1. Convert patient weight to kg. 2. Calculate total daily dose range. 3. Determine doses per day. 4. Calculate dose per administration. 5. Compare with prescribed dose and options.

Clinical Relevance

Nursing practice connection: Use the key finding related to Drug Dosage Calculation to guide bedside assessment, documentation, and the next nursing action.
A core nursing responsibility is to ensure medication safety by verifying that any prescribed dose is within the safe range for the patient's weight. This is one of the 'five rights' of medication administration (right dose).
Nurses must act as a final safety check. If a calculation reveals a discrepancy, as in this case where the prescribed 200 mg dose exceeds the safe maximum of 151.53 mg, the nurse must hold the medication and clarify the order with the prescriber.
What if the ideal dose was 10-40 mg/kg/day? The safe range per administration would become 75.7 mg to 303 mg. In this scenario, the prescribed 200 mg dose would be considered safe.

How to Approach the Question

First, identify all the numerical values provided in the question: patient weight (50 lbs), prescribed dose (200 mg q8h), and ideal dose range (2-20 mg/kg/day).
Note the units. The weight is in pounds (lbs) but the dose is in mg per kilogram (kg). Your first calculation must be to convert lbs to kg.
Calculate the total daily safe dose range (minimum and maximum) using the patient's weight in kg.
Determine the number of doses administered per day based on the frequency (q8h means 3 times a day).
Calculate the safe dose range for a single administration by dividing the daily range by the number of doses.
Finally, compare your calculated per-dose range to the given options to find the best fit. Also, check if the prescribed dose falls within this safe range.

Concept Tested & Keywords

QrzFru1LKbn5VtKXnO4-xj

Practise the full NORCET 10 Prelims-2026

Attempt every question from this paper in a timed mock, then review the full solution for each one.