What do these instructions mean?
I told my parents Latin would be useful!
When it was time to choose a language to study in middle school, I chose Latin with zero hesitation — much to my parents’ chagrin. Not only did I want to learn Latin due to my obsession with Greco-Roman mythology (thanks, Wishbone!), but 11-year-old me wanted to become a psychiatrist one day, and I was convinced I would need to know Latin to get through medical school. Whether it’s condition names, parts of the body, or medications, I thought Latin would be key to learning all of it and make me a more competent health care provider. (You should have seen my face when my pediatrician saw me reviewing my Latin textbook in the waiting room the following year and let me know that learning Latin was not a prerequisite to entering the medical field. Oh well.)
While I did not end up pursuing a career in psychiatry, I’m still glad I studied Latin for as long as I did (seven years of formal education!). Plus, it’s fun to use my Latin skills to decipher the medical jargon I encounter as a chronic illness patient — such as prescription abbreviations, which just so happens to be today’s topic! How the heck did we get all of the shorthand we see on our providers’ prescription pads? Why do we refer to a prescription medication as an “Rx”? Let’s take a look at some of the more common initialisms and acronyms our prescribing health care practitioners use to talk to pharmacists here in the U.S.
The Basics
Rx — General consensus says that this abbreviation comes from the Latin verb recipere, which means “to take or receive.” What the letter X has to do with any of this other than filling in for the remaining letters, I’m not sure. Another theory posits that the true ℞ symbol (in which the R and X intersect) is derived from the ancient Egyptian Eye of Horus, which was used to protect someone from disease and evil. No matter the explanation you turn to, what we do know is that the first recorded prescription was etched into a clay tablet in Mesopotamia around 2400 BCE.
OTC — Of course, prescription medications are available by prescription only, as opposed to over-the-counter medications, which don’t get a fancy Latin name for their category, but you can find in your regular drugstore aisles, rather than behind the pharmacist’s counter.
When Do I Take This?
q, qd, qh, q1h, q2h, et al. — These abbreviations are what I call the “Q Series.” The Q stands for quaque, which means “every” in medical contexts. That’s how we get qd, quaque die, aka “every day,” and qh, quaque hora, meaning “every hour.” Then we can spice up qh by throwing a number in there like with q1h and q2h, which stand for “every one hour” and “every two hours,” respectively. If you want to get really fancy, you can use qhs, quaque hora somni, for medications that need to be taken every night at bedtime.
bid — Bis in die, which means the medication needs to be taken twice a day.
tid — Ter in die is thrice a day (sorry not sorry, I’m always looking for an excuse to use the word “thrice”).
qid — Not to be confused with the “Q Series,” qid comes from the Latin quater in die, meaning “four times a day.”
prn/p.r.n. — This stands for the Latin phrase pro re nata, “under the circumstances” or “as the thing arises.” A prn prescription is one you take as needed — i.e.,when a specific situation or issue arises.
a.c. and p.c. — These initialisms are short for ante cibum and post cibum, which in Latin mean “before food” and “after food,” but in the context of medical prescriptions instructs you to take a medication either before or after meals.
Where Does This Injection Go?
subq/subc/sq/sc/subcut — These are all different ways to shorten the word “subcutaneous,” which describes a medication that gets injected under the skin, specifically into the fatty tissue layer that is between your skin and muscle. Insulin comes in a subcutaneous injection. Bonus Latin tip: If you see the prefix “sub” on a word, it’s usually safe to assume that means “under” whatever the rest of the word is. For instance, a submarine goes under the water.
ID — Intradermal — a word combining the Latin intra, meaning “within,” and the ancient Greek derma, meaning “skin” — refers to an injection that goes into the skin, specifically the dermis, which is the layer underneath the epidermis (the outermost layer of skin). You’ll usually see these needles used in sensitivity testing, such as for allergies or tuberculosis.
IM — I’m sure you can guess that IM, or intramuscular, injections go into the muscle. Most of the vaccines you received as a child were delivered via this route, including DTaP and Tdap (the vaccines that protect you from diphtheria, tetanus, and pertussis).
Extended Release vs. Short-Acting
XR/XL/XT/ER — These all refer to extended-release medications, which last longer in your body and don’t have to be taken as often as their non-extended counterparts. Some extended-release medications may be SR, sustained release, or CR, controlled release. The former slows the process of the medication being released into your body without controlling the levels of the medication, while the latter is able to release the medication in a way that allows it to remain at a constant level in your body for a specific period of time.
IR — As opposed to extended-release medication, IR is short for “immediate release.” Some medications, such as Effexor, come in both XR and IR forms.
Where Does This Tablet, Capsule, Cream, Liquid, etc., Go?
po — Short for per os, which is Latin for “through the mouth,” “po” refers to medication that you’re supposed to take orally, or by mouth. (You’ll soon notice that “per ___” is a common naming convention for medication administration routes.)
pr — Per rectum, which, as you guessed it, means the medication goes up your butt. (OK, OK, into your rectum, if we want to be polite.)
pv — This stands for per vagina, which is also fairly self-explanatory, but means that the medication needs to be inserted into the vagina.
Bonus: What’s Going on With My Eyes and Ears?
OD, OS, and OU — These initialisms stand for the Latin phrases oculus dexter, oculus sinister, and oculus uterque, which mean “right eye,” “left eye” (sorry that you’re called “sinister,” Lefties!), and “each eye” (even though OU is usually used to mean “both eyes” on a prescription), respectively.
AD, AS, and AU — Similar to your eyes, prescriptions pertaining to your ears may be divided into auris dextra, auris sinistra, and auris utraque. Just swap auris for oculus — and feminine adjective endings for masculine ones — and now you’re talking about your ears!
Which prescription abbreviation or other medical terminology etymology do you find fascinating? Let us know! And the next time anyone tells you that Latin is a “dead” language, show them this post!
Sources:
72 Abbreviations Every Pharmacy Tech Needs to Know (Charter College)
Common Prescription Abbreviations for Medication (Verywell Health)
Top 150 Prescription Abbreviations and Their Medical Meanings (Drugs.com)
It's Time to Throw Out Old-Fashioned Latin Abbreviations (Anesthesia Progress via PubMed Central)
Abbreviations in Prescription Writing (Journal of the American Medical Association)
Where Did the Rx Symbol Come From? (HISTORY)
The History of Pharmacy (Texas Tech University Health Sciences Center)
Subcutaneous (SQ) Injections (MedlinePlus)
Sustained Release vs. Extended Release (vs. Other Modified-Release Dosage Forms) (GoodRx)