Things You'Ll Use Every Day In Pharmacy

Things You’ll Use Every Day

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nyone going into the practice of pharmacy will recognize that there is
a lot of memorization involved. Memorization of basic conversions
will be your first step toward mastery of pharmaceutical calculations. By
the end of this lesson, you will be ready to move on to problems where
you will use these facts to solve problems that arise in daily practice.

MeasurementSystems
You may have already encountered the four kinds of measurement systems
used in the world of pharmacy: the metric, apothecaries’, avoirdupois, and
“common” systems.
Metric System
You are probably familiar with metric measurements already. In pharmacy,
you will be dealing with metric measurements of length/height, volume,
and weight. These measurements will be the meter (m), liter (L), andgram
(g), respectively.
It is likely that you know the prefixes that represent multiples or
fractions of these measurements. However, in case you are a bit rusty,
here are the ones you will likely encounter in clinical practice. Be sure
you know all of these.
Abbreviation: Meaning

Example

kilo (k): one thousand

kilogram (kg): drug dosing commonly needs the patient’s
weight in kg

deci (d):one-tenth

deciliter (dL): some drug concentrations are reported as g/dL

centi (c): one-hundredth

centimeter (cm): patient’s height often has to be converted from
inches to cm

milli (m): one-thousandth

milliliter (mL): most injectable drug amounts are in mL

micro (mc or µ): onemillionth

microgram (µg or mcg): some drugs have low serum
concentrations, e.g., µg/L

nano (n): one-billionth

nanogram(ng): some drugs have very low serum
concentrations, e.g., ng/L

pico (p): one-trillionth

picogram (pg): a few drugs have barely detectable
concentrations, e.g., pg/L

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THINGS YOU’LL USE EVERY DAY

Apothecaries’ System
As you can guess from the name, this system was used by the old time
apothecaries—forerunners to today’s pharmacists and pharmacy technicians. In this system, one troy poundwas made up of 5760 grains. The
troy (apothecary) pound was divided into 12 ounces, each of these
ounces (symbol: z) into eight drams (originally spelled “drachm”; symbol: d), each dram into three scruples, and each scruple into 20 grains.
There was also a fluid measure in this system. Here one gallon was
divided into four quarts, each quart into two pints, each pint into 16
fluidounces, eachfluidounce into eight fluidrams, and each fluidram
into 60 minims. Although this may seem overwhelming, you will
nonetheless recognize some of the volume components if you cook.
Here are some relationships involving measures of this system.

Fluid Measures
1 fluidram (fd)
1 fluidounce (fz)
16 fluidounces
32 fluidounces
4 quarts

=
=
=
=
=

60 minims
8 fluidrams
1 pint
1 quart
1 gallon

=
=
=
=

1scruple (X)
3 scruples
=
8 drams
=
12 ounces
=

=

480 minims

=
=

2 pints
8 pints

Solid Measures
20 grains (gr)
60 grains
480 grains
5760 grains

1 dram (d)
1 ounce (z)
1 pound

Avoirdupois System
This system is Roman in origin, has a French name, and was adopted by
the English as a standard for weights in commerce. An avoirdupois (pronounced ah-vwor-doo-pwuh’) pound is divided into 16avoirdupois
ounces. One avoirdupois ounce is made of 437.5 grains.
You will notice that the number of ounces in a pound is different in
this system, compared to the apothecaries’ system, as is the number of
grains (7000 grains per pound in the avoirdupois system versus 5760
grains per pound in the apothecaries’ system). The common measure
between the two systems is the grain, such that a grain in theavoirdupois
system has the same weight as a grain in the apothecaries’ system.
Here’s all you really need to remember: 437.5 grains = 1 ounce
(oz) and 16 ounces = 1 pound (lb). Notice how the avoirdupois
definition of 16 ounces/pound is used in the American system. This is
also the grain definition used in the grain:ounce conversion in pharmacy
practice.
Please double check this with your calculator....