6/24 Memorization

rounding, within- and cross-system conversions, Si prefixes, unit abbreviations, apothecary symbols, roman numerals, compounding instructions, dosage forms, routes, frequency, frequency modifiers and misc. abbrev., indications, units of concentration

are conversions between systems accurate?

not accurate

are conversions within systems accurate?

accurate

golden rule #1

Only change systems when necessary

golden rule #2

Use a conversion appropriate to the scale of the quantity being converted. If possible, use a

direct conversion

golden rule #3

You must use leading zeroes, but do NOT use trailing zeroes. Even if you are asked to give an answer to a certain number of decimal places, if the last digit would be zero, it still must be dropped!

leading zeros

zeros that appear to the left of the first non-zero digit in a number

trailing zeros

zero digits that appear at the end of a number after the last non-zero digit

writing ratios

Ratio strength should be written as a ratio of active ingredient to whole product, simplified to

least whole numbers and separated by a colon.

how to measure tbsp/tps

Write teaspoonful or tablespoonful rather than teaspoon or tablespoon

final answer rounding

If you round intermediate steps you must round to at least one decimal place more than

your final answer, but do not double round

rounding to increments not a multiple of 10

answer will be the multiple of the stated increment that is CLOSEST to the

value being rounded (ex: 1.6mL rounded to 1.5mL, not 1.75mL)

rule of rounding for days

• IF asks how many days (weeks, etc.) a prescription will last the patient, round down; prescription will run out during partial day if rounded up.

• IF asks how long a medication must be given in order to reach a specified total dose, round up; patient will not have reached the target at the beginning of the partial day

rounding rule for drops

round to nearest whole drop

rounding for Discrete dispensing units (tablets or capsules, bottles, jars, IV bags)

• IF the question asks how many will be required to compound a prescription, or the number to be dispensed, round up; patient should receive a full unit for effective treatment.

• If the question asks how many units a prescription will make, ROUND DOWN –

  the partially completed unit will not be dispensed.

infusion pump setting rounding

Round to the nearest 0.1 mL/h unless instructed otherwise.

Freezing point depressions and sodium chloride gram equivalents rounding

If possible, do not round these values. If rounding is necessary, keep at least 3

decimal places.

specific gravity/density rounding

Keep at least 3 decimal places unless instructed otherwise.

density of water

1g/mL

“microdrop
infusion set

60 gtt/mL

normal adult BSA (body surface area)

1.73 m²

density

mass/volume

specific gravity

specific volume

1 nanogram (ng) 

0.001 mcg

1 microgram (mcg or μg) 

1000ng = 0.001mg

1 milligram (mg)

1000μg = 0.001g

1 gram (g)

1000 mg = 0.001 kg

1 kilogram (kg)

1000 g

1 lb in gr

7000

1 lb in oz

16

1 microliter (mcL or µL)

0.001 mL

1 milliliter (mL)

1000 mcL = 0.001 L

1 cc

1 mL

100mL

1 deciliter (dL) = 0.1 L

1 Liter (L)

1000 mL = 10 dL

1 tablespoonful (T)

3 teaspoonsful (tsp)

1 fl oz

2 tablespoonsful (T) = 1/8 cup (c)

1 cup [c]

8 fl oz

1 pint (pt)

2 c = 16 fl oz

1 quart

2 pt = 4 c = 32 fl oz

1 gallon (gal)

4 qt = 8 pt = 16 c = 128 fl oz

1 nanometer (nm)

0.001 µm

1 micrometer (µm)

1 micron = 1000 nm = 0.001 mm

1 millimeter (mm)

1000 µm = 0.001 m

1 centimeter (cm)

10 mm = 0.01 m

1 decimeter (dm)

10 cm = 0.1 m

1 meter (m)

100 cm = 1000 mm = 0.001 km

1 kilometer (km)

1000 m

1 foot (ft or ')

12 inches (in or ")

1 yard (yd)

3 ft

gr i (1 grain) (cross)

65 mg

1 oz (cross)

28.4g

1 lb (cross)

454g

1 kg (cross)

2.2 lb

1 tsp (cross)

5 mL

1 tbsp (cross)

15 mL

1 fl oz (cross)

29.57 mL

1 c (cross)

240 mL

1 pt (cross)

473 mL

1 qt (cross)

946 mL

1 gal (cross)

3785 mL (most accurate)

1 in (cross)

2.54 cm ≈ 25.4 mm

nano (n)

10^-9 (or 0.000000001)

micro (mc OR μ)

10^-6 (or 0.000001)

milli (m)

10^-3 (or 0.001)

centi [c]

10^-2 (or 0.01)

deci (d)

10^-1 (or 0.1)

kilo (k)

10^3 (or 1,000)

mega (M)

10^6 (or 1,000,000)

giga (G)

10^9 (or 1,000,000,000)

U, IU

unit, International Unit

gr (non abbrev.)

grain

lb (non abbrev.)

(Avoirdupois) pound

minim

♏︎,︎ smallest unit of volume

scruple

℈

dram or fluid dram

ʒ (or dr)

ounce or fluid ounce

℥ (bottles)

apothecary pound

℔

forty in roman numerals

XL

fifty in roman numerals

L

sixty in roman numerals

LX

ninety in roman numerals

XC

one hundred in roman numerals

C

five hundred in roman numerals

D

one thousand in roman numerals

M

building roman numerals

List numerals in descending order of size until the sum equals the number to be expressed.

• Exception: A smaller numeral preceding a larger numeral indicates that the smaller value should be subtracted from the larger.

aa (comp)

of each

ad

up to (meaning to fill to the stated quantity)

aq (aq pur; aq dest) 

water (purified water; distilled water)

dtd

give of such doses

div

divide

et

and

ft

make

M (compounding)

make

qs

enough; sufficient quantity

cap or caps

capsule(s)

chart

powder paper

gtt

drops

inh

inhalation

IVBP

IV piggyback (a small IV bag, often hung with, or “piggybacked” onto, a larger-volume IV infusion)