Who can write prescriptions

Who can issue prescriptions is governed by local legislation. In the United States, allopathic physicians, osteopathic physicians, veterinarians, dentists, and podiatrists have full prescribing power. In all states, optometrists prescribe medications to treat certain eye diseases, and also issue spectacle and contact lens prescriptions for corrective eyewear. [14] States allow mid-level practitioners different prescription privileges. Physician assistants (also known as physician associates or PAs), nurse practitioners (also known as advance practice nurses or NPs), and some registered pharmacists currently represent the spectrum of mid-level practitioners.

Each state regulates what (if any) prescription powers members of the above group are allowed. Advance practice nurses and physician assistants have some form of prescriptive authority in all 50 states. But registered pharmacists, for example, have limited prescriptive authority in only 6 states.[15]. Several states have passed RxP legislation, allowing clinical psychologists (PhD's or PsyD's) who have also undergone specialized training in script-writing to prescribe a limited number of drugs to treat emotional and mental disorders.

Prescriptions, when handwritten, are notorious for being often illegible (5% according to an Irish study [16]). Contrary to popular belief, pharmacists do not have special deciphering skills. When in doubt, they call the doctor. At other times, even though some of the individual letters are illegible, the position of the legible letters and length of the word is sufficient to distinguish the medication based on the knowledge of the pharmacist. For doctors that the pharmacist deals with regularly, they learn to read the doctor's handwriting. Patients are advised to ensure that the prescription is legible before leaving the doctor's office. Some jurisdictions have made legible prescriptions a law (e.g. Florida[17]). Some have advocated the elimination of handwritten prescriptions altogether [18] and computer printed prescriptions are becoming increasingly common in some places.

Independent of the actual prescribing decision, elements of a good prescription writing include: [19] [20] [21]
careful use of decimal points to avoid ambiguity:
avoid unnecessary decimal points: 5 mL instead of 5.0 mL to avoid possible misinterpretation of 5.0=50
always zero prefix decimals: e.g. 0.5 instead of .5 to avoid misinterpretation with .5=5
never have trailing zeros on decimals: e.g. use 0.5 instead of .50 to avoid misinterpretation with .50=50
avoid decimals altogether by changing the units: 0.5 g =500 mg
"mL" is used instead of "cc" or "cm³" even though they are technically equivalent
directions should be written out in full in English although some common Latin abbreviations are listed below
quantities can be given directly or implied by the frequency and duration of the directions
where the directions are "as needed" the quantity should always be specified
where possible, usage directions should specify times (7 am, 3 pm, 11 pm) rather than simply frequency (3 times a day) and especially relationship to meals for orally consumed medication
use permanent ink
avoid unspecified prn or "as needed" instructions—limits and indicators should be provided e.g. "every 3 hours prn pain"
for refills, minimum duration between repeats and number of repeats should be specified
provide the indication for all prescriptions even when obvious to the prescriber so that the pharmacist may identify possible errors
avoid non-standardized units such as "teaspoons" or "tablespoons"
write out numbers as words and numerals ("dispense #30 (thirty)") as in a bank draft or cheque

See Appendix 1 for a complete list of common abbreviations found on prescriptions. Many abbreviations are derived from Latin phrases. Hospital pharmacies have more abbreviations, some specific to the hospital. Different jurisdictions follow different conventions on what is abbreviated or not. Prescriptions that don't follow area conventions may be flagged as possible forgeries.

Some abbreviations which are ambiguous, or which in their written form might be confused with something else, are not recommended and should be avoided. These are included in a separate list in Appendix 1. However, all abbreviations carry an increased risk for confusion and misinterpretation and should be used cautiously.