The Pharmaceutics and Compounding Laboratory
Prescriptions and Medication Orders

Preparation of Prescription Medications

Accurate preparation and dosing are achieved only through systematic adherence to a given series of steps. Errors which occur at any step in this process will result in reduced accuracy of dosing to the patient. These steps include:

  1. Identify the required elements of a prescription.
  2. Review and interpretation (translation) of the prescription.
  3. Calculations of measurable quantities of all components.
  4. Accurate weight/measurement of all components.
  5. Use of appropriate compounding techniques to convert individual components into a finished product.
  6. Proper packaging and labeling of the product.
  7. Delivery of the correct, completed product to the correct patient with adequate instructions for administration.

Reviewing, interpreting and labeling the presciption involves a "language" that must be learned and utilized. Part of that language includes abbreviations. The health-care professions use an estimated 10,000 abbreviations. There are no guidelines about which abbreviations can be used in written orders, although many institutions have developed some criteria. The pharmacist typically encounters a variety of abbreviations. These might be grouped in the following categories:

  • Latin Terms
    Traditionally prescriptions are written in Latin. In recent years physicians have tended to write their prescriptions in English or with very abbreviated Latin instructions. A brief list of terms is available, but the best way to understand the terms is to practice interpreting prescriptions.
  • Drug Name Abbreviations
  • Medical Abbreviations

Many abbreviations are used in only a limited geographical area or institutional setting, so care must be taken when interpreting any abbreviation. For example, the abbreviation T.I.W. can be interpreted as "three times a week" or "twice a week." D/C can be interpreted as "Drug Information Center", "discharge", or "discontinue." HS could mean "at bedtime" or "half-strength."

Frequently the physician omits the "fl" or "f" which should precede the unit sign when liquid measure is intended. The pharmacist must determine whether a volume or weight measurement is intended. Pertinent rules for making such a decision are as follows:

  • If the ingredient is a liquid in a liquid preparation, then the quantity is a volume.
  • If the ingredient is a solid, then the quantity is a weight.
  • In an ointment or other solid preparation, the quantities are always by weight, unless otherwise specified.

Other translation problems come from misreading quantities. You should always remember that quantities may be expressed in metric or apothecary units, and occasionally a prescription will contain both. It is essential that you translate these units into the proper, measurable amounts.

Many other translation problems come from misreading the actual drug or ingredient name. Many drugs appear similar when written or sound alike when spoken. An extensive list of common look-alike, sound-alike drugs is provided.