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Strength, Amount, Route & Frequency

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After you write the medication name, you need to tell the pharmacist the desired strength. Many, if not most, medications come in multiple strengths. You need to write which one you want. Often times, the exact strength you want is not available, so the pharmacist will substitute an appropriate alternative for you. For example, if you write prednisone (a corticosteroid) 50 mg, and the pharmacy only carries 10 mg tablets, the pharmacist will dispense the 10 mg tabs and adjust the amount the patient should take by a multiple of 5.


Using my previous example for prednisone, the original prescription was for 50 mg tabs. The prescriber would have written “prednisone 50 mg, one tab….” (I’ll leave out the rest until we get there). The “one tab” is the amount of the specific medication and strength to take. Again using my previous example, the instructions would be rewritten “prednisone 10 mg, five tabs….” You can see that “one tab” was changed to “five”. Pharmacists make these changes all the time, often without any input needed from the physician.


Up until this point, we have been using plain English for the prescriptions. The route is the first opportunity we have to start using English or Latin abbreviations. A NOTE: it is often suggested that to help reduce the number of medication errors, prescription writing should be 100% English, with no Latin abbreviations. I will show you both and let you decide. There are several routes by which a medication can be taken: By Mouth (PO), Per Rectum (PR), Sublingually (SL), Intramuscularly (IM), Intravenously (IV), Subcutaneously (SQ)

As you can see, the abbreviations are either from Latin roots like PO – per os – or just common combination of letters from the English word. Unfortunately when you are in a hurry and scribbling these prescriptions, (there is a truth behind never being able to read a physician’s hand writing) many of these abbreviations can look similar. For example, intranasal is often abbreviated “IN,” which, when you are in a hurry, can be mistaken for “IM” or “IV.” Check this out:

Common Route Abbreviations:

  • PO (by mouth)
  • PR (per rectum)
  • IM (intramuscular)
  • IV (intravenous)
  • ID (intradermal)
  • IN (intranasal)
  • TP (topical)
  • SL (sublingual)
  • BUCC (buccal)
  • IP (intraperitoneal)

The frequency is simply how often you want the prescription to be taken. This can be anywhere from once a day, once a night, twice a day or even once every other week. Many frequencies start with the letter “q.” Q if from the Latin word quaque which means once. So it used to be that if you wanted a medication to be taken once daily, you would write QD, for “once daily” (“d” is from “die,” the Latin word for day). However, to help reduce medication errors, QD and QOD (every other day) are on the JCAHO “do not use” list. Instead you need to write “daily” or “every other day.”

Common Frequencies Abbreviations:

  • daily (no abbreviation)
  • every other day (no abbreviation)
  • BID/b.i.d. (Twice a Day)
  • TID/t.id. (Three Times a Day)
  • QID/q.i.d. (Four Times a Day)
  • QHS (Every Bedtime)
  • Q4h (Every 4 hours)
  • Q4-6h (Every 4 to 6 hours)
  • QWK (Every Week)

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