A physician orders a medication to be administered to a patient in a dose of 200mg twice daily (BD). The pharmacy provides tablets of the medication, with each tablet containing 0.1g of the active ingredient?

Appeared in: NORCET 6 Prelims -2024

Explanation

The first critical step is to ensure both the ordered dose and the available dose are in the same unit. The order is in milligrams (mg) and the tablets are in grams (g).
Using the standard conversion factor where 1 gram equals 1000 milligrams, the available tablet strength is converted: 0.1 g is equivalent to 100 mg.
The drug calculation formula (Dose Ordered / Dose on Hand) is then applied.
Calculation: 200 mg (ordered) divided by 100 mg (on hand per tablet) equals 2.
Therefore, the nurse must administer 2 tablets to deliver the correct 200 mg dose.

Option A: Administering 1 tablet would only provide 100 mg of the medication, which is half of the prescribed 200 mg dose. This would lead to under-dosing and potential therapeutic failure.
Option C: Administering 3 tablets would result in a total dose of 300 mg (3 x 100 mg), which is 100 mg more than the prescribed dose. This constitutes a medication error and an overdose.
Option D: Administering 4 tablets would deliver 400 mg of the medication, double the prescribed dose. This is a significant overdose and a serious medication error that could harm the patient.

Visual 1: Infographic - A simple chart showing the conversion between grams (g) and milligrams (mg) with the key fact '1 g = 1000 mg' highlighted.
Visual 2: Flowchart - A step-by-step flowchart illustrating the drug calculation process: 1. Identify Ordered Dose. 2. Identify Available Dose. 3. Check Units (Convert if necessary). 4. Apply Formula. 5. Calculate Final Answer.

Clinical Relevance

Nursing practice connection: Use the key finding related to Drug Dosage Calculation and Unit Conversion to guide bedside assessment, documentation, and the next nursing action.
Accurate drug calculation is a fundamental competency for nurses and a cornerstone of safe medication administration. Errors can lead to significant patient harm, from therapeutic failure (under-dosing) to toxicity (over-dosing).
Nurses should always perform the 'Triple Check' before administering any medication: 1. When retrieving the medication from storage. 2. When preparing the medication. 3. At the patient's bedside before administration.
What if the available tablets were 0.2 g each? In that case, 0.2 g equals 200 mg. The calculation would be (200 mg / 200 mg) = 1 tablet. This shows how a change in the available stock strength directly impacts the calculation.

How to Approach the Question

Step 1: Identify the 'Dose Ordered' from the question, which is 200 mg.
Step 2: Identify the 'Dose on Hand' or available strength, which is 0.1 g per tablet.
Step 3: Compare the units of the ordered dose (mg) and the available dose (g). Recognize they are different and a conversion is required before any calculation.
Step 4: Convert the available dose to the same unit as the ordered dose. Recall or look up that 1 g = 1000 mg. Calculate: 0.1 g * 1000 = 100 mg.
Step 5: Apply the standard formula for solid medications: (Dose Ordered / Dose on Hand) = Number of Tablets.
Step 6: Substitute the values into the formula: (200 mg / 100 mg) = 2 tablets. Select the option that matches this result.

Concept Tested & Keywords

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Practise the full NORCET 6 Prelims -2024

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