Principles of Prescription Writing Dr Sasan Zaeri (PharmD, PhD) Department of Pharmacology

Definition A prescription is a written, verbal, or electronic order from a practitioner or designated agent to a pharmacist for a particular medication for a specific patient

Prescription drug Drug that requires a prescription because it is considered potentially harmful if not used under the supervision of a licensed health care practitioner

Types of Prescriptions Generic Name The nonproprietary name (based on pharmacological group) e.g., Amoxicillin, Fluoxetine, Diazepam, Aspirin Brand Name The proprietary name provided by pharmaceutical company who holds the patent on the drug e.g., Prozac®, Viagra®, Xanax®

Types of Prescriptions (cont’d) Compounded Requires the preparation of one or more active ingredients with one or more pharmaceutical necessities, e.g., suspending agent, flavoring agent, to create a finished product. For example, an oral compounded prescriptions may be used to facilitate the administration of a solid dosage form that is not available in liquid form for patients unable to swallow a solid dosage form. e.g., pediatric, geriatric

Types of Prescriptions (cont’d New An original prescription order dispensed for the first time Refill A repeat dispensing of the original prescription order

Prescription Formatting Heading Body Closing

Sample Prescription-

Prescription Formatting Heading Name, address, and telephone number of the prescriber Validates prescription Provides contact information to clarify any questions Name, sex and age of the patient Age is important if for a pediatric or geriatric patient Date of the prescription to validate refills, to ensure pt supervision

Prescription Formatting Body The Rx symbol Drug dosage form Drug name Dose size or concentration Quantity to be dispensed (#) Directions to the patient

Contents of the Prescription Selecting the drug Medication Allergies Availability Cost

Contents of the Prescription Abbreviations of dosage forms Tablets - Tab Capsule – Tap Syrup – Syr Suspension – Susp Injection – Inj Lotion – as such Spray- as such

Contents of the Prescription Name of the drug- CAUTION: Be very cautious about drug names that “sound/look” alike e.g. Flagyl vs. Plasil

Contents of the Prescription Name of the drug- AVOID the use of Abbreviations DO NOT use abbreviations for drugs prescribed unless the abbreviation is official and routine: SSKI (Saturated Solution of Potassium Iodide) NS (Normal Saline) NTG (Nitroglycerin) MTX (Methotrexate) MOM (Milk of Magnesia)

Contents of the Prescription Strength of the drug Be familiar with drugs various dosing strengths and dosage forms When in doubt, use references Writing no strength means prescribing the lowest available strength

Contents of the Prescription Strength of the drug Decimal points Avoid trailing zeros EX. 5 mg vs. 5.0 mg; can be mistaken for 50 mg Always use leading zeros. EX. 0.8 ml vs. .8 ml; can be mistaken for 8 ml

Synthroid (levothyroxine) Avoid a tenfold overdose. Place a zero before the decimal point.

Avoid potential tenfold overdoses. Never follow drug doses with a decimal point and zero. (example of dilaudid (hydromorphone)1mg was read as 10 mg)

Contents of the Prescription Quantity of the drug (#) Avoid writing a prescription for a large quantity of drug unless it is absolutely determined that such a quantity is necessary For chronic medication, it is better to start with a lower number at first in the event that the patient cannot tolerate it because of side effects Economic considerations (Limitation by insurance organizations)

Contents of the Prescription Quantity of the drug Quantity (#) = frequency per day x treatment days

Contents of the Prescription Directions for use Avoid “as directed” as far as possible Write out in full English or use Latin abbreviations

Contents of the Prescription Latin abbreviations – more convenient, more potential for mistakes Avoid Dangerous Abbreviations

List of dangerous abbreviations, acronyms, and symbols Potential Problem Preferred Term U (unit) Mistaken as zero, four, cc Write “unit” ug Mistaken as mg Write “microgram” IU (international unit) Mistaken as IV or 10 Write “international unit” Q.D Mistaken for QID Period after Q can be mistaken for “I” Write “daily” MS, MSO4, MgSO4 Confused for one another Write “morphine sulfate” or “magnesium sulfate”

A handwritten "u" can look like a zero, a four, or "cc." Always write out "unit." (all three problems illustrated above)

can sometimes look like The abbreviation "q.d." can sometimes look like "q.i.d." Always spell out the word "daily."

Rules for writing amount of drug: Quantities of 1 gram or more should be written in grams. Ex - write 2 g Quantities less than 1 gram but more than 1 milligram should be written in Milligrams For e.g, write 100 mg, not 0.1 g

Quantities less than 1 milligram should be written in microgram DO NOT abbreviate micrograms eg. write 100 micrograms, not 0.1 mg, nor 100 mcg, nor 100 μg

Prescription Formatting Heading Body Closing

Prescription Formatting Closing Generic substitution instructions Refill instructions Prescriber’s signature

Determine preference for brand or generic product Brand vs. generic Is Brand always better? NO If practitioner prefers brand, must indicate in print, - do not substitute or brand necessary

Sample Prescription-

Contents of the Prescription Refills To avoid interrupting maintenance therapy Refills “N” times or NR. Leaving this section blank implies that the prescription is non- refillable a prescription refill for a conventional, non-controlled medication has a one year expiration time

MAXIMIZE PATIENT SAFETY ALWAYS write legibly Use the same pen for the entire prescription If a mistake is made, e.g., number of tablets, cross out the mistake, write “error” above it, and then initial it AVOID abbreviations When in doubt, ask to verify

CASE #1 Poor handwriting contributed to a medication dispensing error that resulted in a patient with depression receiving the antianxiety agent Buspar 10 mg instead of Prozac 10 mg

CASE #2 A hypertensive patient accidentally received Vantin (cefpodoxime) 200 mg instead of Vasotec (enalapril) 20 mg when a pharmacist misread this prescription

Can you read this? Tegretol (carbamazepine) or TEQUIN (gatifloxacin) ???