Pharmacy Practice for the CPhT: Understanding Roman Numerals

What is the additive rule for Roman numerals?

Add values when equal or smaller symbols follow larger symbols.

What is the subtractive rule for Roman numerals?

Subtract the smaller value from the larger value within a valid subtractive pair.

What are the six standard subtractive pairs?

IV, IX, XL, XC, CD, and CM.

Which symbols can I be subtracted from?

V and X.

Which symbols can X be subtracted from?

L and C.

Which symbols can C be subtracted from?

D and M.

How should a Roman numeral containing a subtractive pair be calculated?

Group the subtractive pair first, then add the remaining values.

What is I in Arabic numerals?

1.

What is II in Arabic numerals?

2.

What is III in Arabic numerals?

3.

What is IV in Arabic numerals?

4.

What is V in Arabic numerals?

5.

What is VI in Arabic numerals?

6.

What is VII in Arabic numerals?

7.

What is VIII in Arabic numerals?

8.

What is IX in Arabic numerals?

9.

What is X in Arabic numerals?

10.

What is XI in Arabic numerals?

11.

What is XII in Arabic numerals?

12.

What is XIII in Arabic numerals?

13.

What is XIV in Arabic numerals?

14.

What is XV in Arabic numerals?

15.

What is XVI in Arabic numerals?

16.

What is XVII in Arabic numerals?

17.

What is XVIII in Arabic numerals?

18.

What is XIX in Arabic numerals?

19.

What is XX in Arabic numerals?

20.

What is XXI in Arabic numerals?

21.

What is XXII in Arabic numerals?

22.

What is XXIII in Arabic numerals?

23.

What is XXIV in Arabic numerals?

24.

What is XXV in Arabic numerals?

25.

What is XXVI in Arabic numerals?

26.

What is XXVII in Arabic numerals?

27.

What is XXVIII in Arabic numerals?

28.

What is XXIX in Arabic numerals?

29.

What is XXX in Arabic numerals?

30.

What is XXXI in Arabic numerals?

31.

What is XXXII in Arabic numerals?

32.

What is XXXIII in Arabic numerals?

33.

What is XXXIV in Arabic numerals?

34.

What is XXXV in Arabic numerals?

35.

What is XXXVI in Arabic numerals?

36.

What is XXXVII in Arabic numerals?

37.

What is XXXVIII in Arabic numerals?

38.

What is XXXIX in Arabic numerals?

39.

What is XL in Arabic numerals?

40.

What is L in Arabic numerals?

50.

What is XC in Arabic numerals?

90.

What is C in Arabic numerals?

100.

What is CD in Arabic numerals?

400.

What is D in Arabic numerals?

500.

What is CM in Arabic numerals?

900.

What is M in Arabic numerals?

1,000.

How is 49 correctly written in Roman numerals?

XLIX, not IL.

What does “Take II tablets” mean?

Take 2 tablets.

What does “Take V mL” mean?

Take 5 mL.

What does “Take I–II tablets” mean?

Take 1–2 tablets.

What does “Dispense XXX tablets” mean?

Dispense 30 tablets.

What does “Dispense XV capsules” mean?

Dispense 15 capsules.

Which numeral system should be used when writing medication doses and concentrations?

Arabic numerals.

Why should Roman numerals be avoided when writing medication doses?

They can be confused with letters or other numbers and contribute to medication errors.

What should a technician do if prescription notation is unclear?

Refer it to the pharmacist for clarification rather than guessing.

What does a concentration of 5 mg/5 mL mean?

There are 5 milligrams of medication in every 5 milliliters of product.