training and knowledge is required than can be given here.
It is the intent of this section to familiarize you with the basics of compounding, in order that you may understand and fully appreciate the complexities involved in bringing the correct medication, properly prepared, to the patient.
ETHICS OF COMPOUNDING
Since the patient is of prime importance when compounding medicines, the corpsman must be a person of integrity, skill, and knowledge. Accuracy, both in kind and amount is of utmost importance, as is cleanliness and orderliness, to ensure the proper manufacture of medicinal substances.
Pharmaceutical compounding is not an area for shortcuts or substitution, nor is there room for dishonest or haphazard attitudes.
PHARMACEUTICAL PROCESSES
In order to understand the principles of compounding, we must first be familiar with some of the physical processes involved.
Comminution
Comminution is the process of physical reduction of a substance to fine particle size, which makes the substance or drug easier to dissolve and compound.
The processes for comminution are cutting, grating, grinding, pulverizing, trituration, and levitation. The first four terms are self-explanatory and are employed primarily on animal and vegetable drugs from which we wish to extract active principles.
TRITURATION—This is a process of reducing a solid to a very fine powder by grinding in a mortar and pestle, which will be described in detail later in this chapter. LEVITATION—Solids can be ground to even finer subdivision by adding a small amount of liquid to make a paste and triturating further. This process is ideal for ointments, creams, and lotions.
Processes of Separation
A important phase of compounding medicines is that of separating solids from liquids by various means. The main purpose is to purify the liquid, but the process is also employed to obtain certain desirable solids from liquids.
DECANTATION—Probably the simplest method of separating solids from liquids is the process of recantation, which merely means letting the solids settle to the bottom of the container and pouring off the liquid by gently tilting the container.
COLATION—When the solids in a liquid are fairly large, a simple method of separation is passing the mixture through a strainer, cheesecloth, or muslin, allowing the fluid to pass through and retaining the solids.
FILTRATION—This is the process of separating a solid from a liquid with the purpose of obtaining the liquid in a clear transparent state, devoid of impurities. The liquid, called the filtrate, is passed through a porous barrier called the filter. The filtering medium may be paper, paper pulp, asbestos, cotton, felt, sand, or other suitable material.
In pharmacy, we have commercial filter paper readily available for this purpose, and in large installation, mechanical filtering machines filter large quantities in a fraction of the time otherwise required.
CENTRIFUGATION—Solids are separated from liquids by the centrifugal force or rotation.
PRECIPITATION—In this method, solids are formed from previously clear solutions by either physical or chemical means and then separated by filtration or other previously mentioned means.
HEAT
Heat is a very important tool in compounding and must be thoroughly understood.
Heat is a form of energy and is measured in degrees. Two common scales of temperature are in use today, Fahrenheit, based on the freezing point of water as 32° and the boiling point as 212°; and Celsius (centigrade) with the freezing point of water as 0° and the boiling point as 100°. The Celsius scale is now used in almost all temperature determinations, such as scientific work, the weather, etc. Unless otherwise specified, all temperatures given in the USP-NF and Remington’s Pharmaceutical Sciences are Celsius.
Thermometers are instruments for measuring the intensities of heat. Most of these instruments are based on the expansion of liquids and vary only in the purpose for which they were intended.