Prescriptions have been obfuscated by a combination of Latin and English abbreviations (sometimes they even throw in Greek words). They are commonly used on prescriptions to communicate essential information on formulations, preparation, dosage regimens, and administration of the medication. There are approximately 20,000 medical abbreviations; instead of providing an exhaustive and meaningless list, this article will focus on the most common medical abbreviations that are necessary for interpreting prescriptions and medical orders.

Common medical abbreviations

The following lists are broken into five categories including route, dosage form, time, measurement, and a catch all category simply named "other." The abbreviations can often be written with or without the 'periods' and in upper or lower case letters (e.g., p.o. and PO both mean 'by mouth'). The format on these lists will be to provide the abbreviation, followed by its intended meaning.

Route

aa - affected area
a.d. - right ear
a.s. - left ear
a.u. - each ear
IM - intramuscular
IV - intravenous
IVP - intravenous push
IVPB - intravenous piggyback
KVO - keep vein open
n.g.t. - naso-gastric tube
n.p.o. - nothing by mouth
nare - nostril
o.d. - right eye
o.s. - left eye
o.u. - each eye
per neb - by nebulizer
p.o. - by mouth
p.r. - rectally
p.v. - vaginally
SC or SQ - subcutaneously
S.L. - sublingually (under the tongue)
top. - topically

Some additional notes on these routes of administration are necessary. The abbreviation 'a.d.' if written without periods, ad, can also mean to or up to. Also, subcutaneously can be abbreviated as 'SC' or 'SQ'. While amongst health care professionals we would use the phrase sublingual as a route of administration, it may be necessary to translate 'SL' as 'under the tongue' for many patients.

Dosage form

amp. - ampule
aq or aqua - water
caps - capsule
cm or crm - cream
elix. - elixir
liq. - liquid
sol. - solution
supp. - suppository
SR, XR XL - slow/extended release
syr. - syrup
tab. - tablet
ung. or oint - ointment

The abbreviation 'cm' can be translated as either 'cream' or 'centimeter'. Use context clues from the rest of the prescription to determine which translation is appropriate.

Time or how often

a.c. - before food, before meals
a.m. - morning
atc - around the clock
b.i.d. or bid - twice a day
b.i.w. or biw - twice a week
h or ° - hour
h.s. - at bedtime
p.c. - after food, after meals
p.m. - evening
p.r.n. or prn - as needed
q.i.d. or qid - four times a day
q - each, every
q.d. - every day
q_h or q_° - every__hour(s) (i.e., q8h would be translated as every 8 hours)
qod - every other day
stat - immediately
t.i.d. or tid - three times a day
t.i.w. or tiw - three times a week
wa - while awake

Measurement

i, ii, ... - one, two, etc. (often Roman numerals will be written on prescriptions using lowercase letters with lines over top of them)
ad - to, up to
aq. ad - add water up to
BSA - body surface area
cc - cubic centimeter
dil - dilute
f or fl. - fluid
fl. oz. - fluid ounce
g, G, or gm - gram
gr. - grain
gtt - drop(s)
l or L - liter
mcg or μg - microgram
mEq - milliequivalent
mg - milligram
ml or mL - milliliter
q.s. - a sufficient quantity
q.s. ad - add a sufficient quantity to make
ss - one-half (commonly used with Roman numerals to add a value of 0.5)
Tbs or T - tablespoon
tsp or t - teaspoon
U - unit
> - greater than
< - less than

Other

c - with
disp. - dispense
n/v - nausea and vomiting
neb - nebulizer
NR - no refills
NS or NSS - normal saline, normal saline solution
s - without
Sig or S - write, label
SOB - shortness of breath
T.O. - telephone order
ut dict or u.d. - as directed
V.O. - verbal order

Parts of a prescription

Traditionally, a prescription is a written order for compounding, dispensing, and administering drugs to a specific client or patient and once it is signed by the physician it becomes a legal document. Prescriptions are required for all medications that require the supervision of a physician, those that must be controlled because they are addictive and carry the potential of being abused, and those that could cause health threats from side effects if taken incorrectly, for example, cardiac medications, controlled substances, and antibiotics.

The following is a list of the parts of a prescription:

• Patient Information, which may include information such as name, address, age, weight, height, and allergies.
• Superscription, which is the 'Rx' symbol that we typically translate as, "Take thus."
• Inscription, which is the actual medication or compounding request.
• Subscription, or how much to dispense.
• Signatura, which is the instruction set intended for the patient.
• Date, this is when the prescription was written. prescriptions for medications and supply that are not considered controlled substances are good for up to 1 year from when the prescription was written.
• Signature lines, which is where the prescriber provides their signature and indicates their degree. Often, this is also where a prescriber may indicate their preferences with regard to generic substitution.
• Prescriber information, which includes the physician's name, practice location address, telephone number and fax number. This may also include the prescriber's NPI number and appropriate license numbers.
• DEA#, DEA numbers are required for controlled substances.
• Refills, which simply indicates how many refills may be supplied for a particular medication.
• Warnings, which are provided by the prescriber with the intention of emphasizing specific concerns.

So, if we look at a prescription for Patricia Pearson (see below), we can see that it is for Lipitor (atorvastatin Ca) 20 mg tablets, and that the patient is to receive 30 of them with 2 refills. The instructions to the patient would be, “Take 1 tablet by mouth daily.”

Other things of note include the date that the prescription is written for is August 31, 2013. Prescriptions for non-controlled substances are only good for one year, so Mrs. Pearson will need a new script if she still needs this medication past August 31, 2014, regardless of how many refills were written for. Another noteworthy item is that the physician signed permitting product selection (i.e., generic substitution). The last significant item on this label is that the physician did not include their DEA number. A DEA number should only be used for controlled substances.

Besides over the counter medications (OTC) such as aspirin and ibuprofen, behind the counter medications (BTC) such as Allegra-D (fexofenadine with pseudoephedrine), and prescription medications (Rx legend) such as amoxicillin and digoxin, there is another group of medications to be concerned with called controlled substances. Controlled substances are medications with further restrictions due to abuse potential. There are 5 schedules of controlled substances with various prescribing guidelines based on abuse potential, as determined by the Drug Enforcement Administration and individual state legislative branches. CI medications are not available via a prescription. CII medications may be written for a maximum 90 day supply excluding hospice patients. No refills are allowed on schedule II medications. CIII-IV medications may only be written for a 6 month supply. CV medications may be written for up to 1 year, although many states limit this to 6 months.

Error prone abbreviations

There are a number of abbreviations and dose designations that can be misinterpreted. Below is a list of some of the more commonly misinterpreted abbreviations and dose designations.

μg - microgram - mistaken as "mg" - to avoid confusion use "mcg"
U or u - unit - mistaken for "0" (zero), the number "4" (four) or "cc" - to avoid confusion write "unit"
IU - International Unit - mistaken for "IV" (intravenous) or the number "10" (ten) - to avoid confusion write "International Unit"
Q.D., QD, q.d., or qd - daily - mistaken for qod (every other day) or "qid" (four times a day) - to avoid confusion write "Daily"
Q.O.D., QOD, q.o.d., or qod - every other day - the period after the Q mistaken for "I" and the "O" mistaken for "I" causing confusion with "qid" - to avoid confusion write "every other day"
q.i.d., or qid - four times a day - the "I" may be missed or mistaken for a "." or a "O" causing confusion with "qd" and "qod" - to avoid confusion write "four times a day"
TIW or tiw - three times a week - misinterpreted as twice a week - to avoid confusion write "three times a week" or list the specific days
Trailing zero (X.0 mg) - means X mg - the decimal point may be missed and read as "X0 mg" - to avoid confusion don't use a trailing zero
Lack of leading zero (.X mg) - means 0.X mg - Without a leading zero, the decimal can be missed causing "X mg" to be dispensed - to avoid confusion write "0.X mg"
MS - Can mean morphine sulfate or magnesium sulfate and therefore can be misinterpreted - to avoid confusion write "morphine sulfate" or "magnesium sulfate"
MSO4 and MgSO4 - morphine sulfate and magnesium sulfate - they can be confused for one another - to avoid confusion write "morphine sulfate" or "magnesium sulfate"

See also

Medication order entry and fill process
Medication safety

References

1. Pharmaceutical Calculations, v. 1.0, Sean Parsons, Parsons Printing Press, ISBN: 978-0578063737, pp 171-204, 275-298, 2012
2. The Commonwealth Fund, Medication Mistakes: Types and Causes, http://www.commonwealthfund.org/Performance-Snapshots/Medication-Mistakes-and-Adverse-Drug-Events/Medication-Mistakes--Types-and-Causes.aspx