Ampicillin is prescribed by the doctor to a client is 150 mcg and tablets available in 0.1mg. How much tablets should be given to the patient?

Appeared in: NIMHANS Nursing Officer - 2019

Explanation

The core task is a drug dosage calculation that requires unit conversion before applying the standard formula.
First, convert the available tablet strength from milligrams (mg) to micrograms (mcg) to match the prescribed dose unit. The conversion factor is 1 mg = 1000 mcg.
The available tablet strength is 0.1 mg, which is equivalent to 0.1 × 1000 = 100 mcg.
Next, use the dosage calculation formula: (Desired Dose / Stock Dose) × Quantity.
The calculation is (150 mcg / 100 mcg) × 1 tablet, which equals 1.5 tablets.

Option B: Administering 1 tablet would only provide 100 mcg of the medication, which is less than the prescribed 150 mcg. This would result in underdosing the patient.
Option C: Administering 3 tablets would provide 300 mcg (3 × 100 mcg), which is double the prescribed dose. This is a significant medication error and could lead to overdose and toxicity.
Option D: Administering 2 tablets would provide 200 mcg (2 × 100 mcg), which is an overdose compared to the prescribed 150 mcg. This could result from a calculation error or incorrect rounding.

Clinical Relevance

Nursing practice connection: Use the key finding related to Drug Dosage Calculation to guide bedside assessment, documentation, and the next nursing action.
Accurate drug calculation is a fundamental nursing responsibility to ensure patient safety and prevent medication errors, which can lead to underdosing (ineffective treatment) or overdosing (toxicity).
Nurses must always adhere to the 'Six Rights of Medication Administration': Right Patient, Right Drug, Right Dose, Right Route, Right Time, and Right Documentation.
What if? If the tablet was not scored (i.e., could not be accurately split in half), the nurse should not attempt to break it. Instead, the nurse must contact the pharmacy to see if a different strength or liquid formulation is available, or consult the prescriber for an alternative order.

How to Approach the Question

First, identify the key information provided: the prescribed or desired dose (150 mcg) and the available or stock dose (0.1 mg per tablet).
Recognize that the units of measurement are different (mcg and mg). To perform the calculation, you must convert them to a single, consistent unit.
Recall the conversion factor: 1 mg = 1000 mcg. Convert the available dose to mcg: 0.1 mg × 1000 = 100 mcg per tablet.
Apply the standard dosage calculation formula: (Desired Dose / Stock Dose) × Quantity.
Substitute the values into the formula: (150 mcg / 100 mcg) × 1 tablet.
Calculate the result, which is 1.5 tablets, and select the corresponding option.

Concept Tested & Keywords

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E6 Pharmacology Nurses Shanbhag 3e pp. 51-53, 52-54

E6 Nursing Fundamentals Potter Perry 12e Part 3 p. 142-144

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