From the wrong drug prescribed to the wrong dosage or administration schedule advised, dispensed, or administered, the impact of medication misadventures is a costly problem. Errors of these sorts occur because human beings are involved, and such errors can be prevented only by systems that make it difficult to do the wrong thing. This appendix provides a primer on the proper approach to the medication prescription and order process and a resource for practitioners in effectively providing pharmaceutical care for their patients.
THE MECH ANICS OF PRESCRIPTION ORDER WRITING
Early medicines were made up of multiple ingredients requiring complex preparation, and Latin was adopted as the standard language of the prescription to ensure understanding between physician and pharmacist and consistency in pharmaceutical composition. Latin no longer is the international language of medicine, but a number of commonly used abbreviations derive from old Latin usage. The symbol "Rx" is said to be an abbreviation for the Latin word recipere, meaning "take" or "take thus," as a direction to a pharmacist, preceding the physician's "recipe" for preparing a medication. The abbreviation "Sig" for the Latin Signatura, is used on the prescription to mark the directions for administration of the medication.
The prescription consists of the superscription, the inscription, the subscription, the signa, and the name and signature of the prescriber, all contained on a single form (Figure AI–1).
The prescription. The prescription must be carefully prepared to identify the patient and the medication to be dispensed, as well as the manner in which the drug is to be administered. Accuracy and legibility are essential. Use of abbreviations, particularly Latin, is discouraged, because it leads to dispensing errors. Inclusion of the therapeutic purpose in the subscription (e.g., "for control of blood pressure") can prevent errors in dispensing. For example, the use of losartan for the treatment of hypertension may require 100 mg/day (1.4 mg/kg/day), whereas treatment of congestive heart failure with this angiotensin II receptor antagonist generally should not exceed 50 mg/day. Including the therapeutic purpose of the prescription also can assist patients in organizing and understanding their medications. In addition, including the patient's weight on the prescription can be useful in avoiding dosing errors, particularly when drugs are administered to children.
The superscription includes the date the prescription order is written; the name, address, weight, and age of the patient; and the Rx (Take). The body of the prescription, or inscription, contains the name and amount or strength of the drug to be dispensed, or the name and strength of each ingredient to be compounded. The subscription is the instruction to the pharmacist, usually consisting of a short ...