PTCB Certified Pharmacy Technician (PTCE)MedicationsMedium
A pharmacy technician is preparing a non-sterile compound that requires the use of a Class A prescription balance. According to USP <1176> 'Prescription Balances and Volumetric Apparatus,' what is the minimum weighable quantity for a Class A balance with a sensitivity requirement of 6 mg and a maximum acceptable error of 5%?
- A120 mg
- B12 mg
- C6 mg
- D600 mg
Show answer & explanationAnswer & explanation
Correct answer: A. 120 mg
The minimum weighable quantity (MWQ) is calculated using the formula: MWQ = Sensitivity Requirement / Maximum Acceptable Error. So, MWQ = 6 mg / 0.05 = 120 mg.
Why the other options are wrong
- B. This would be the MWQ if the error was 50%, which is incorrect.
- C. This is the sensitivity requirement, not the MWQ.
- D. This is incorrect and would imply a much smaller acceptable error.
Minimum Weighable Quantity (MWQ)
The smallest amount of a substance that can be accurately weighed on a given balance, considering its sensitivity and an acceptable error percentage.
- Ensures accuracy in compounding
- Calculated using sensitivity and acceptable error
- Essential for potent substances
Memory trick: Mighty Weighing Quantities Ensure Accuracy.