A doctor order 3 types of medicines for a 2 years old baby includes methotrexate 100 mg , Hydroxyzine 50 mg , paracetamol 150 mg to give OD. All medicines available in 100 mg/1 ml injection. Calculate the total required dose of for the patient?

Appeared in: NORCET 3 - 2022 (Shift-2)

Explanation

The core task is to calculate the volume in mL for three separate medication orders and then sum them.
The universal formula used is Volume = Dose Ordered / Concentration.
For Methotrexate: 100 mg / (100 mg/mL) = 1.0 mL.
For Hydroxyzine: 50 mg / (100 mg/mL) = 0.5 mL.
For Paracetamol: 150 mg / (100 mg/mL) = 1.5 mL.
The total volume is the sum of the individual volumes: 1.0 + 0.5 + 1.5 = 3.0 mL.

Option A: This value (2.0 mL) would be incorrect. It might result from a calculation error, such as miscalculating the paracetamol dose as 0.5 mL instead of 1.5 mL (1.0 + 0.5 + 0.5 = 2.0).
Option B: This value (2.5 mL) is incorrect. It could be the result of adding the volumes incorrectly or miscalculating one of the drug volumes, for example, calculating paracetamol as 1.0 mL (1.0 + 0.5 + 1.0 = 2.5).
Option C: This value (1.5 mL) is incorrect. This is the volume for paracetamol alone and does not account for the other two medications.

Visual 1: Infographic: 'The 5 Rights of Medication Administration' to emphasize the importance of the 'Right Dose'.
Visual 2: Flowchart: 'Steps for Calculating and Administering Liquid Medications' showing the process from order to administration, including the verification step.

Clinical Relevance

Nursing practice connection: Use the key finding related to Medication Dosage Calculation (Total Volume) to guide bedside assessment, documentation, and the next nursing action.
A nurse's primary duty is to act as a patient advocate and safety net. This includes critically evaluating all medication orders for appropriateness and safety.
The doses of Methotrexate and Hydroxyzine in this scenario are extremely high for a 2-year-old and represent a potentially fatal medication error. Such an order must be questioned immediately.
What if the order was written correctly but transcribed incorrectly? Always perform an independent check. If a nurse had administered these doses, they would be held professionally and legally responsible for the resulting harm, despite it being a doctor's order.

How to Approach the Question

First, identify what the question is asking for: the 'total required dose' in mL.
Next, break down the problem into smaller parts. Note the three different medications and their ordered doses.
Identify the 'dose on hand' or concentration, which is 100 mg/mL for all medications.
Use the standard formula (Volume = Dose Ordered / Concentration) to calculate the volume for each of the three medications separately.
Finally, add the three calculated volumes together to find the total volume.
As a final safety check, critically assess if the calculated dose seems reasonable for the patient, although in an exam context, the mathematical answer is what is being tested.

Concept Tested & Keywords

Concept Tested: Medication Dosage Calculation (Total Volume)
Stem keywords: methotrexate, hydroxyzine, paracetamol, dose calculation, total required dose, 2 years old
Lead-in keywords: Calculate
Clinical cues: Patient is a 2-year-old child, which requires careful dose verification.
Clinical cues: Multiple medications are ordered, requiring calculation for each and then summation.

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Practise the full NORCET 3 - 2022 (Shift-2)

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