Section II. PERCENTAGE PREPARATIONS
Many of the prescriptions received in the pharmacy have the amounts of active
ingredients expressed as percentage strengths as opposed to a weight or volume which
can be measured. The physician knows that each active ingredient, when given in a
certain percentage strength, gives the desired therapeutic effect. Instead of the
physician calculating the amount of each ingredient needed for the prescription, he will
simply indicate the percentage strength desired for each ingredient and expect the
pharmacy to calculate the amount of each ingredient based on its percentage strength.
There are no percentage weights for a torsion balance or percentage graduations on a
graduate. The percentage values on a prescription must be changed to amounts which
can be weighed (grams) or to amounts which can be measured (milliliters).
2-5. TYPES OF PERCENT
Recall that the term percent means "parts per hundred" and is expressed in the
# OF PARTS
a. W/W percent or Weight/Weight percent is defined as the number of grams in
100 grams of a solid preparation.
(1) Example #1 A 5 percent (w/w) boric acid ointment would contain 5 grams
of boric acid in each 100 grams of boric acid ointment.
(2) Example #2:A 3 percent (w/w) vioform powder would contain 3grams of
vioform in every 100 grams of the vioform powder.
b. W/V of Weight/Volume percent is defined as the number of grams in 100
milliliters of solution.
(1) Example #1:A 10 percent (w/v) potassium chloride (KCL) elixir would
contain 10 grams of potassium chloride in every 100 milliliters of KC1 elixir.
(2) Example #2:A 1/2 percent (w/v) phenobarbital elixir would contain 1/2
gram of phenobarbital in every 100 milliliters of phenobarbital elixir.
c. V/V percent or Volume/Volume percent is defined as the number of milliliters
in every 100 ml of solution.
(1) Example #1:A 70% (v/v) alcoholic solution would contain 70 milliliters of
alcohol in every 100 ml of solution.