PTCE - Order Entry and Processing - Section 4.1

Apply formulas, calculations, ratios, proportions, conversions, Sig codes, abbreviations, medical terminology, and symbols to determine days supply, quantity, dose, concentration, and dilutions. (Calculation-based.)

Apply pharmacy calculations - including ratio-proportion, concentration and dilution formulas, and metric unit conversions - to determine days supply, dose, and dispensing quantity. Interpret Sig codes, Latin abbreviations, Roman numerals, and medical symbols accurately to enter and verify orders.

Sig codeDays supply calculationConcentration calculationRoman numerals

Practice question for this objective

Free sampleOrder Entry and Processinghard

A handwritten prescription for a controlled medicine specifies the quantity in Roman numerals as tablets quantity xxiv, with the directions i tab po q6h prn pain. The technician must enter both the dispensed quantity and the maximum days supply if the patient uses every dose. Which entry is correct?

  • AQuantity 26 tablets, maximum days supply 6 days, reading the numeral as twenty plus six and using four doses each day.
  • BQuantity 24 tablets, maximum days supply 4 days, treating q6h as six doses spread across each twenty-four hour period.
  • CQuantity 16 tablets, maximum days supply 4 days, reading xxiv as fourteen plus two and dividing by four doses daily.
  • DQuantity 24 tablets, maximum days supply 6 days, taking one tablet every six hours as up to four doses per day. Correct
Interpret a Roman numeral quantity and a q6h prn Sig to derive dispensed quantity and the maximum days supply at full use. The numeral xxiv decodes as twenty plus four, giving 24 tablets, and q6h means a dose every six hours or four doses per twenty-four hours, so the longest the supply lasts at maximum use is 24 divided by 4, which is 6 days.

Why A is wrong: The days supply logic is sound, but xxiv is 24, not 26; misreading iv as 6 instead of 4 inflates the dispensed quantity by two tablets.

Why B is wrong: The quantity is read correctly, but q6h means every six hours, which is four doses a day, not six, so dividing 24 by 6 understates the days supply.

Why C is wrong: This both misreads the numeral and miscounts, since xxiv is 24 not 16; the q6h to four doses step is right but applied to the wrong quantity.

Why D is correct: Roman numeral xxiv is 24, q6h prn allows up to four doses daily, and 24 tablets divided by 4 per day gives a maximum of 6 days supply when every dose is taken.

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