METHODS USED TO PREPARE EMULSIONS
Emulsions are infrequently prepared in the pharmacy. Thus, this subcourse will
not provide detailed instructions for the preparation of emulsions. You should be aware
that several methods exist for the preparation of this dosage form. The two methods
most frequently used are the continental method and the bottle method.
a. Continental Method (4-2-1 Method). This is the most commonly used
method for the preparation of emulsions. The common name, the 4-2-1 Method,
describes the ratio of fixed oil, water, and acacia used to prepare the basic emulsion.
For specific information on this method, see Remington's Pharmaceutical Sciences.
b. Bottle Method. This method is used to prepare small quantities of volatile oil
emulsions. In this method, two parts of oil, two parts of water, and one part of
powdered acacia is used. As the name implies, the basic emulsion is prepared in a
bottle by vigorously shaking the components. Again, for specific information about this
method, consult Remington's Pharmaceutical Sciences.
ADDITION OF OTHER INGREDIENTS TO EMULSIONS
Any number of different medicinals may be incorporated into the emulsion. It
would be impossible to go into any detail in the exact procedure to take for each
substance in specific situations. The following general information can be adapted to
a. Water-soluble ingredients are dissolved in water and added after the
formation of the primary emulsion.
b. Oil-soluble ingredients are dissolved in the oil before emulsification.
c. Insoluble ingredients should be finely powdered and triturated into the product
just before it is brought up to final volume.
d. It is best to add syrups and glycerin directly to the formed primary emulsion.
They should not be added in large quantities.
e. Alcoholic solutions, electrolytes, and other materials which are likely to cause
the emulsion to crack must be diluted to as weak a concentration as possible and added
to the product just before it is brought up to its final volume.