Medical prescription

# Overview
A medical prescription (Template:Unicode) is an order (often in written form) by a qualified health care professional to a pharmacist or other therapist for a treatment to be provided to their patient. A prescription is a legal document which not only instructs in the preparation and provision of the medicine or device but indicates the prescriber takes responsibility for the clinical care of the patient and the outcomes that may or may not be achieved.

# Format and definition
Prescriptions are typically  handwritten on preprinted prescription forms that are assembled into pads, or alternatively printed onto similar forms using a computer printer.  Preprinted on the form is text that identifies the document as a prescription, the name and address of the prescribing provider and any other legal requirement such as a registration number (e.g. DEA Number in the United States).  Unique for each prescription is the name of the patient.  In the United Kingdom the patient's name and address must also be recorded. Each prescription is dated and some jurisdictions may place a time limit on the prescription.  There is the specific "recipe" of the medication and the directions for taking it.  Finally there is the doctor's signature.
The symbol "Rx" meaning "prescription" is a transliteration of a symbol resembling a capital R with a cross on the diagonal (Template:Unicode).
The word "prescription" can be decomposed into "pre" and "script" and literally means, "to write before" a drug can be prepared.  Those within the industry will often call prescriptions simply "scripts".

## Contents of the prescription
Both pharmacists and prescribers are regulated professions in most jurisdictions.  A prescription as a communications mechanism between them is also regulated and is a legal document.  Regulations may define what constitutes a prescription, the contents and format of the prescription (including the size of the piece of paper - see Exhibit C paragraph 10) and how prescriptions are handled and stored by the pharmacist.  Many jurisdictions will now allow faxed or phone prescriptions containing the same information.  Exhibit A below illustrates the legal definition of a prescription.
Many brand name drugs have less expensive generic drug substitutes that are chemically equivalent.   Prescriptions will also contain instructions on whether the prescriber will allow the pharmacist to substitute a generic version of the drug.  This instruction is communicated in a number of ways.  In some jurisdictions, the preprinted prescription contains two signature lines:  one line has "dispense as written" printed underneath; the other line has "substitution permitted" underneath.  Some have a preprinted box "dispense as written" for the prescriber to check off (but this is easily checked off by anyone with access to the prescription).  Other jurisdictions the protocol is for the prescriber to handwrite one of the following phrases: "dispense as written", "DAW", "brand necessary", "do not substitute", "no substitution", "medically necessary", "do not interchange".
As a guideline, pediatric prescriptions should include the age of the child if the patient is less than twelve and the age and months if less than five.  (In general, including the age on the prescription is helpful.)  In some jurisdictions, it may be a legal requirement to include the age of  child on the prescription .   Adding the weight of the child is also helpful.
Prescriptions often have a "label" box .  When checked, pharmacist is instructed to label the medication.  When not checked, the patient only receives instructions for taking the medication and no information about the prescription itself.
Some prescribers further inform the patient and pharmacist by providing the indicator for the medication; i.e. what is being treated.  This assists the pharmacist in checking for errors as many common medications can be used for multiple medical conditions.
Some prescriptions will specify whether and how many "repeats" or "refills" are allowed; that is whether the patient may obtain more of the same medication without getting a new prescription from the doctor.  Regulations may restrict some types of drugs from being refilled.
In group practices, the preprinted portion of the prescription may contain multiple prescribers' names.  Prescribers typically circle themselves to indicate who is prescribing or there may be a checkbox next to their name.

## Handling of the prescription
When filled by a pharmacist, as a matter of business practice, the pharmacist may write certain information right on the prescription.  This may also be mandated by legislation (see Exhibit D).  Information such as the actual manufacturer of the drug and the date the medication was dispensed may be written right onto the prescription.  Legislation may require the pharmacist sign the prescription.  In computerized pharmacies, all such information is printed and stapled to the prescription.  Sometimes such information is printed onto labels and the labels affixed right onto the prescription.
When filled by the pharmacist, prescriptions are typically assigned a "prescription number" (often abbreviated "Rx#") that is unique to the pharmacy that filled the prescription.  The prescription number is written right on the prescription by the pharmacist.  The prescription number has the practical purpose of uniquely identifying the prescription later on while filed (both manual and electronic).   The prescription number is also put on the label on the dispensed medication.  The patient may be required to reference the prescription number for refills and drug insurance claims.  There may also be a legal requirement for prescription numbers for subsequent identification purposes.
As a legal document, some jurisdictions will mandate the archiving of the original paper prescription in the pharmacy.   Often the patient cannot take the original prescription with them.  Some jurisdictions may entitle patients to a copy.  The retention period varies but can be as long as six years.   See Exhibit B for sample legislation governing the archiving of prescriptions.   Once the retention period has passed, privacy legislation may dictate what can be done with the original paper prescription.  Legislation may also dictate what happens to the prescriptions if the pharmacy closes or is sold.  For example, if the pharmacy goes out of business, the pharmacist may be required to return the prescription to the patient, to the next closest pharmacy or to the governing body for pharmacists.
Prescriptions for non-narcotic drugs may also be "transferred" from one pharmacy to another for subsequent repeats to be dispensed from another pharmacy.  The physical piece of paper that is the prescription is not transferred, but all the information on it is transferred from one pharmacy to another.  Legislation may dictate the protocol by which the transfer occurs and whether the transfer needs to be noted on the original paper prescription.
It is estimated that 3 billion (3 thousand million) prescriptions were written in the United States in 2002.  This number has grown from 1.5 billion in 1989 and is expected to continue to grow.

## Forgeries, thefts and prevention
Prescriptions are sometimes forged because many narcotics are cheaper and safer as prescription drugs than as street drugs. Forgery takes many forms:  Prescription pads are sometimes stolen, amounts may be altered on legitimate prescriptions, call back numbers may be falsified and phoned or faxed prescriptions faked.
Some doctors will use prescription pads that contain similar security measures as checks to make photocopying prescriptions harder.  These security measures may be mandated by lawsee Exhibit C for sample legal specifications.  Legislation may mandate that only certain printers may print prescriptions.  New Jersey, for example, requires that only state approved printers may be used to print official "New Jersey Prescription Blanks."  (See Exhibit E.)  Prescribers can make it harder for amount forgeries by writing out the amounts in words.  Again, this may be mandated by law.
Some jurisdictions help control stolen prescriptions by requiring special "triplicate prescriptions" for certain classes of drugs . Blank triplicates are only available from the regulating agency and are individually numbered. The doctor retains a copy, the second and third copies are given to the patient to give to the pharmacist. The pharmacist retains the second copy and the third copy is submitted to the regulating agency. The regulating agency can issue lists of stolen prescriptions that pharmacists can check. In this example, the prescription's validity is further limited to 72 hours from issuance. This system also has the further benefit of managing "double doctoring" where patients visit multiple doctors to get prescriptions. California has recently replaced tripicate forms with new forms that are impossible to photocopy or fax: the background is printed with repetitions of the word void in a color that shows up as black on a photocopy.
States have various laws making theft of prescription blanks or forgery of prescriptions criminal offenses and/or providing special treatment for these offenses (for Example N.J. Stat. 2C:21-1. making forgery of a prescription blank a third degree rather than fourth degree offense).
When forgery is suspected, pharmacists will call the doctor to verify the prescription and will attempt to detain the suspect pending arrival of authorities. Forged prescriptions are no longer considered medical documents and doctor-patient confidentiality rules no longer apply.

# Writing prescriptions

## 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.  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), currently represent the spectrum of mid-level practitioners. Each state regulates what 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. Registered pharmacists, too, have limited prescriptive authority in only 6 states.. 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.

## Legibility of prescriptions
Prescriptions, when handwritten, are notorious for being often illegible (5% according to an Irish study ). 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).  Some have advocated the elimination of handwritten prescriptions altogether  and computer printed prescriptions are becoming increasingly common in some places.

## Writing good prescriptions
Independent of the actual prescribing decision, elements of a good prescription writing include:
- 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
- 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" instructionslimits 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

## Abbreviations
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.

# Non prescription drug prescriptions
Prescriptions are also used for things that are not strictly regulated as a prescription drug.  Prescribers will often give non-prescription drugs out as prescriptions because drug benefit plans may reimburse the patient only if the over-the-counter medication is taken under the direction of a doctor.   Conversely, if a medication is available over-the-counter, doctors may ask patients if they want it as a prescription and possibly incur a pharmacist's dispensing fee or whether they want to get it themselves at a lower price.   If the patient wants the medication not under prescription, the prescriber is usually careful to give the medication name to the patient on a blank piece of paper to avoid any confusion with a prescription.  This is applied to non-medications as well.  For example, crutches, and registered massage therapy may be reimbursed under some health plans, but only if given out by a prescriber as a prescription.
Prescribers will often use blank prescriptions as general letterhead.   A "doctor's note" for absent days from school or work for minor illnesses will often be written on a blank prescription.
Legislation may define certain equipment as "prescription devices".  Such prescription devices can only be used under the supervision of authorized personnel and such authorization is typically documented using a prescription.  Examples of prescription devices include dental cement (for affixing braces to tooth surfaces), various prothesis, gut sutures, sickle cell tests, cervical cap and ultrasound monitor.
In some jurisdictions, hypodermic syringes are in a special class of their own, regulated as illicit drug use accessories separate from regular medical legislation.   Such legislation will often specify a prescription as the means by which one may legally possess syringes.

# Related usage of the term prescription
Prescription may also be used as a short form for prescription drugs to distinguish from over-the-counter drugs.   It may also be used in reference to the entire system of controlling drug distribution (as opposed to illicit drugs).  "Prescription" is often used as a metaphor for healthy directions from authority.  A "green prescription" is direction from a doctor to a patient  for exercise and healthy diet.

# History
The concept of prescriptions dates back to the beginning of history. So long as there were medications and a writing system to capture directions for preparation and usage, there were prescriptions .
Modern prescriptions are actually "extemporaneous prescriptions" from the Latin (ex tempore) for "at/from time" .   "Extemporaneous" means the prescription is written on the spot for a specific patient with a specific ailment.  This is distinguished from a non-extemporaneous prescription which is a generic recipe for a general ailment.  Modern prescriptions evolved with the separation of the role of the pharmacists from that of the physician . Today the term "extemporaneous prescriptions" is reserved for "compound prescriptions" which requires the pharmacist to mix or "compound" the medication in the pharmacy for the specific needs of the patient.
Predating modern legal definitions of a prescription, a prescription traditionally is composed of four parts:  a "superscription", "inscription", "subscription" and "signature".
The superscription section contains the date of the prescription and patient information (name, address, age, etc).  The symbol "Rx" separates the superscription from the inscriptions sections.  In this arrangement of the prescription, the "Rx" is a symbol for recipe or literally the imperative "take."  This is an exhortation to the pharmacist by the doctor, "I want the patient to have the following medication" - in other words, "take the following components and compound this medication for the patient."
The inscription section defines what is the medication. The inscription section is further composed of one or more of:
- a "basis" or chief ingredient indended to cure (curare)
- an "adjuvant" to assist its action and make it cure quickly (cito)
- a "corrective" to prevent or lessen any undesirable effect (tuto)
- a "vehicle" or "excipient" to make it suitable for administration and pleasant to the patient (jucunde)
The "subscription" section contains dispensing directions to the pharmacist.   This may be compounding instructions or quantities.
The "signature" section contains directions to the patient  and is often abbreviated "Sig." or "Signa."  It also obviously contains the signature of the prescribing doctor though the word "signature" has two distinct meanings here and the abbreviations are sometimes used to avoid confusion.
Thus sample prescriptions in modern textbooks are often presented as:

# Future directions of prescriptions
As a prescription is nothing more than information among a prescriber, pharmacist and patient, information technology can be applied to it.   Existing information technology is adequate for electronic prescriptions.   Medical information systems in some hospitals do away with prescriptions within the hospital.   There are proposals to securely transmit the prescription from the doctor to the pharmacist using smartcards and the internet.  In the UK a project called the Electronic Transfer of Prescriptions (ETP) within the National Programme for IT (NPfIT) is currently piloting such a scheme between doctors and pharmacies.
Within computerized pharmacies, the information on the piece of paper that is the prescription is captured immediately.   Thereafter, the prescription is simply an entry within the pharmacy's information system and the paper prescription is stored for legal reasons only.
In cases where a pharmacy is part of a chain of pharmacies, the pharmacies are often linked together through their corporate headquarters with computer technology.  Walgreens, for example, uses satellite technology to share patient information.  A person who has a prescription filled at one Walgreens can get a refill of that prescription at any other store in the chain, as well as have their information available for new prescriptions at any Walgreens.
Some online pharmacies also offer services to customers over the internet.  Walgreens' web site, for example, allows customers to order refills for medicine over the internet, and allows them to specify the store that they will pick up the medicine from.  Their web site also allows consumers to lookup their prescription history, and to print it out.
Many pharmacies now offer services to ship prescription refills right to the patient's home. CVS, for example, will ship refills free of charge. They also offer mail service where you can mail in a new, original prescription and a signed document, and they will ship the filled prescription back to you.
Pharmacy information systems are a potential source of valuable information for pharmaceutical companies as it contains information about doctor's prescribing habits.  Prescription data mining of such data is a developing, specialized field.
Although computerized information systems offer attractive improvements to paper-based prescriptions, they are not yet available in many prescribers' practices. To reduce prescribing errors, some investigators have developed modified prescription forms that prompt the prescriber to provide all the desired elements of a good prescription. The modified forms also contain pre-defined choices such as common quantities, units and frequencies that the prescriber may circle rather than write out. Such forms are thought to reduce errors (especially omission and handwriting errors) and are actively under evaluation. (See: Kennedy AG, Littenberg B. A Modified Outpatient Prescription Form to Reduce Prescription Errors. Joint Commission Journal of Quality and Safety 2004; 30:480-487.)

# Appendix 1: Partial list of abbreviations
This appendix is a list of some abbreviations used in prescriptions.  Its listing here does not mean such abbreviations should be used. See main article for discussion on the use of abbreviations. This listing does not include abbreviations for actual pharmaceuticals (which is a separate article in itself). Capitalization and the use of a period is a matter of style. In the attached list, Latin is not capitalized whereas English acronyms are. The period is used wherever there are letters omitted in the abbreviation.
To avoid ambiguity, the following abbreviations are not recommended :
- a.u., a.s., a.d. - Latin for both, left and right ears; the "a" can be misread to be an "o" and interpreted to mean both, right  or left eyes
- d/c - can mean "discontinue" or "discharge"
- h.s. - can mean half strength or "hour of sleep"
- q.d. - meant "every day" but the "." after the "q" is interpreted to be an "i" thus "q.i.d." or quadrupling the dose to 4 times a day
- q.o.d. - meant "every other day" but the "o" can be interpreted as "." or "i" resulting in double or eight times the frequency
- SC/SQ - meant "subcutaneaous" but mistaken for "SL" for "sublingual"
- T.I.W - meant 3 times a week but mistaken for twice a week
- U - meant "units" but mistaken for "0", "4" or "cc" when poorly written; conversely cc can be mistaken for "U"
- g - meant "microgram" but mistaken for "mg"; this 1000-fold error can cause potentially fatal misunderstandings

# Exhibit A:  sample legal definition of a prescription
Taken from California's Business and Professions Code Section 4040 

# Exhibit B: sample legal requirement for storage of prescriptions
From the Mississippi Board of Pharmacy :

# Exhibit C: sample legal requirements for security and format
From Indiana Board of Pharmacy :

# Exhibit D: sample requirements on information added by the pharmacist
Taken from the Ontario's Drug and Pharmacies Regulation Act
, paragraph 156.

# Exhibit E: New Jersey requirements for prescription blanks
From New Jersey official statutes: