This section is from the book "Practical Materia Medica And Prescription Writing", by Oscar W. Bethea. Also available from Amazon: Practical Materia Medica and Prescription Writing.
The inscription is that part which contains the name of the drug or drugs ordered and the amount desired. It is usually best written in Latin.
Some inscriptions may be divided into the following parts:
Basis, or principal ingredient.
Adjuvant-that which aids the action of the principal ingredient.
Corrective-that which modifies some undesirable action of the other ingredients. Vehicle-that which facilitates the dispensing or administration of the other ingredients.
This is sometimes called the diluent or solvent and in the case of ointments is often called the base.
For example:
Chlorali Hydrati............................................. | 3iss |
Potassii Bromidi............................................. | 3iss |
Syr. Aurantii...................................................... | f3ij |
Aquae....................................................................... | q. s. |
M.
Here the hydrated chloral is the most active agent. The bromide aids the action of the basis. The syrup of orange modifies the unpleasant taste and tendency to nausea of the other agents. The water dissolves and dilutes.
It is often impossible to definitely classify the parts of an inscription. There may be more than one drug belonging to a class, as sodium bromide and potassium bromide may be ordered in equal amounts in the same prescription.
The same agent may act as a member of two or more classes, as in the following, where chloroform-water may be regarded as adjuvant, corrective, and vehicle at the same time:
Sodii Bromidi...................................................... | 3ij |
Aquae Chloroformi.......................................... | q. s. |
Of course, a large percentage of the prescriptions written only call for one or two items.
Each item and the character expressing its amount should be on one line except under circumstances as mentioned later.
In using unruled blanks, care should be exercised that the characters designating the quantity of an ingredient should be on a line with the name of the drug.
The total amounts of the ingredient should be specified in the inscription.
Sometimes a prescriber will specify the amount of each dose, and then order so many of such doses to be made. This practice is to be unqualifiedly condemned. It requires as much writing as the common method. It is so unusual that it may be overlooked or misunderstood by the pharmacist, and an educated physician should not throw the burden of making calculations on a drug clerk of unknown ability.
The following will illustrate:
Hydrarg. Chlor. Mitis............................................... | gr. j |
Sacchari Lactis............................................................ | gr. x |
M. ft. cht. mitte talis no. iij.
This was submitted to twenty registered pharmacists in one of our large cities, and five out of the twenty understood that the quantities as given were to be divided into three doses containing 1/3 of a grain of calomel to each dose.
It is better, for the sake of appearance and conformity to custom, to begin each word, forming a part of the name of an ingredient, with a capital letter, as:
Tinct. Opii Camph. Sodii Bromidi.
 
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