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).

Recall that the term percent means "parts per hundred" and is expressed in the

following manner:

# OF PARTS

100 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.

MD0802

2-12

Integrated Publishing, Inc. |