PTCE - Medications - Section 1.7

Apply drug stability requirements for oral suspensions, insulins, reconstitutables, injectables, and vaccinations. (Calculation-based.)

Apply drug stability requirements - including beyond-use dates, reconstitution instructions, and refrigeration windows - to oral suspensions, reconstitutables, injectables, insulins, and vaccines. Calculate or determine when a preparation has exceeded its stability limit and must be discarded.

Drug stabilityReconstitutionBeyond-use dateInsulin stability

Practice question for this objective

Free sampleMedicationsmedium

A technician reconstitutes a dry amoxicillin suspension on 4 June. The manufacturer label states the product is stable for 14 days when stored in the refrigerator after mixing. The dispensing software prompts the technician to apply the shorter of the manufacturer stability period or any pharmacy default. No shorter pharmacy default applies. What beyond-use date should the technician place on the label?

  • A18 June Correct
  • B11 June
  • C4 December
  • D19 June
Calculate a reconstituted suspension beyond-use date by adding the manufacturer stability period to the reconstitution date. Reconstituting a dry suspension begins the stability clock, so the beyond-use date is the reconstitution date plus the manufacturer stated number of days; 4 June plus 14 days lands on 18 June.

Why A is correct: Counting 14 days from the 4 June reconstitution date gives 18 June, matching the manufacturer stability period that governs reconstituted suspensions.

Why B is wrong: This applies a 7-day period, which is a common default for some reconstituted products but contradicts the 14-day figure stated on this label.

Why C is wrong: A 6-month dating reflects the dry powder shelf life before mixing, not the much shorter stability of the reconstituted liquid.

Why D is wrong: This counts 14 days but starts from the day after reconstitution, adding an extra day beyond the manufacturer period.

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