The Use of Prescription Abbreviations: A Brief History
Latin once served a greater role on prescriptions when they were first written in the 1400s. Spread widely by Roman soldiers and traders, Latin was the main language of western Europe for hundreds of years. It was unlikely to change, because it was a "dead" language, and it was unlikely to be misinterpreted, because it was exact in its meaning. Patients who didn't know Latin probably didn't have the slightest idea what they were taking.
Today, the only part of a prescription where Latin still appears is in the directions for taking the drug. This use has become a kind of medical shorthand between doctors and pharmacists. Some of these abbreviated terms have the potential to cause medication errors because they look so similar in handwriting, so their use is slowly on the decline.
The Origins of Using "Rx" for "Prescription"
Where does the "Rx" for "prescription" come from? Its origins are given variously as an abbreviation of the Latin word "recipe," meaning "take," or as a representation of the astrological sign of Jupiter. This sign was placed on ancient prescriptions to invoke that deity's blessing on the medicine to help the person get well. More recently, the cross that sometimes appears at the end of the "R" has been explained as a substitute period.
The Use of Prescription Abbreviations: An Example
An example of what your doctor may write:
Sig: I tab po qid pc & hs
Unless you have a medical background, that bunch of letters is probably unintelligible. In this example, the prescription abbreviations instruct the pharmacist to, "Label the container for this patient's medication with the following instructions: Take one tablet by mouth 4 times a day, after meals and at bedtime."
Prescription Abbreviations: Common Latin Rx Terms
Some of the common latin prescription abbreviations include:
- ac (ante cibum) means "before meals"
- bid (bis in die) means "twice a day"
- gt (gutta) means "drop"
- hs (hora somni) means "at bedtime"
- od (oculus dexter) means "right eye"
- os (oculus sinister) means "left eye"
- po (per os) means "by mouth"
- pc (post cibum) means "after meals"
- prn (pro re nata) means "as needed"
- q 3 h (quaque 3 hora) means "every 3 hours"
- qd (quaque die) means "every day"
- qid (quater in die) means "4 times a day"
- Sig (signa) means "write"
- tid (ter in die) means "3 times a day"
For an In-Depth Listing of Prescription Abbreviations:
- Prescription And Other Medical Abbreviations
A comprehensive listing and explanation of commonly used prescription and other medical abbreviations, from The Department of Pharmaceutical Sciences at the State University of New York at Buffalo.
Prescription Abbreviations: Use Slowly in Decline
While Latin terms are still commonly seen on prescriptions, some doctors are gradually retiring use of these old terms and better clarifying their drug orders in plain language.
Since improved readability helps prevent medication mix-ups, it has been recommended that prescribers write out instructions rather than use more ambiguous abbreviations. (For example, write "daily" rather than "qd," the abbreviated Latin term for "every day," which could be misinterpreted as "qid," meaning "4 times a day," or "od," meaning "right eye.")
Prescription Abbreviations: The Bottom Line
If the directions written on a prescription are unclear or confusing, please ask your doctor or pharmacist to explain. Do not take your medication without fully understanding the prescribing instructions.
Making It Easier to Read Prescriptions, by Dixie Farley, FDA Consumer Magazine, July-August 1995