b. Method. The left, or IF, side of the equation should be the concentration of
the drug in stock. The right, or THEN, side of the equation should be the ratio solute
dose/solution dose, or ordinarily weight dose/volume dose.
c. Example 1. The labeled strength of a 30 ml vial of Meperidine (Demerol)
injection is 50 mg/ml. How many milliliters must be injected to provide a 75 mg dose?
IF 50 mg
50 X = 1 75
50X = 75
= 1.5 ml, answer
d. Example 2. A preparation of Morphine is labeled with a concentration of 30
mg/cc. How many milliliters must be injected to provide a 1/8 grain dose?
First, we must convert 1/8 grain to the metric system. Using a conversion
factor (1 gr = 60 mg), we calculate that 1/8 gr = 7.5 mg.
IF 30 mg THEN 7.5 mg
30 X = 7.5 1
X = 0.25
(Rounding off, X = 0.3 ml, answer)
1-21. ANTIBIOTIC DILUTIONS
a. Antibiotic drugs such as Penicillins, Streptomycin, and the Tetracyclines often
are manufactured and supplied to you in the form of a sterile powder in a vial which
must be reconstituted with sterile water for injection, normal saline solution, or other
suitable diluent (solvent) (Table 1-12). This presents special problems and
considerations not normally seen with prepared injection solutions. Specifically, you
must STOP and consider each of the following problems when handling antibiotics for