Principles of Prescription Writing Dr Sanjeewani Fonseka Department of Pharmacology

History Prescriptions have been in use since ancient times Latin adopted as standard language “Rx” = prescription

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

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.

Writing Prescriptions Who can write a Rx? Practitioners Physicians, veterinarians, dentists

Prescription Formatting Heading Body Closing

Current Prescription Formatting Heading Body Closing

Current Prescription Formatting Heading Name, address, and telephone number of the prescriber Name, sex and age of the patient Date of the prescription 3

Contents of the Prescription Patient Name and Address Full first and last name Middle initial may be helpful DOB – not required, but will be helpful in further identifying the correct patient to prevent medication errors

Contents of the Prescription Practitioner’s Name, Address, and Phone number Validates prescription Provides contact information to clarify any questions

Contents of the Prescription Date Date the prescription is issued or written Allows the determination of the life of the prescription to validate refills Ensures continual patient supervision Promotes patient follow - up

Current Prescription Formatting Heading Body Closing

Current Prescription Formatting Body The Rx symbol Name dose size or concentration (liquids) of the drug Amount to be dispensed Directions to the patient 4

Contents of the Prescription Selecting the drug Medication Allergies Availability Cost

Contents of the Prescription Name of the drug Multiple drugs per prescription can add to confusion KEEP IT SIMPLE

Contents of the Prescription Name of the drug - CAUTION: Look Alike/Sound Alike drug names Massive number of new drug releases Massive number of reformulations Drug marketing strategy Build on established names New combination drugs – Use converged names

Contents of the Prescription Name of the drug AVOID THE USE OF: Abbreviations Many drugs identified with abbreviations EX: HCT for hydrochlorothiazide, MSO4 for morphine sulfate Attempts to standardize abbreviations have been unsuccessful

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

Tablets - tab Capsule – cap Syrup – syr Suspension – susp Injection – Inj Metered dose inhaler – as such Lotion – as such

Contents of the Prescription Strength of the drug Be familiar with drugs and their various dosing strengths and dosage forms When in doubt, use references

Dosing cont; Weight – based dosing Always convert patient weight to correct units (kg) Liquid medications One product may be available in a number of concentrations Be familiar with various product concentrations Indicate BOTH concentration and dose of medication Example: Cephalexin suspension 125 mg/ 5 ml 1 teaspoon/ every 8 h

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

Contents of the Prescription Quantity of the drug Prescribe only necessary quantity Write for specific quantities rather than time period (for example: dispense #30 vs. dispense for 1 month) Calculate: quantity = frequency per day x treatment days Writing out “Dispense # X” is helpful

Rules for writing quantity 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 eg, write 100 mg, not 0.1 g

Quantities less than 1 milligram should be written in micro / nano gram as appropriate. DO NOT abbreviate micro/ nanograms; since that can lead to Prescribing errors. For eg. write 100 micrograms, not 0.1 mg, nor 100 mcg, nor 100 μg Use ml or mL for milliliters

For some drugs, a maximum dose may need to be stated ( for eg For some drugs, a maximum dose may need to be stated ( for eg. ergotamine in migraine & colchicine in gout). Eg: Ergotamine 1 mg at onset of attack & repeat every 30 min if necessary . Do not take more than 6 mg in one day or more than 12mg in one week

Contents of the Prescription Directions for use Write out in full English or use Latin abbreviations Latin abbreviations – more convenient, more potential for mistakes Avoid Dangerous Abbreviations Provide clear and specific directions

Should be clearly indicated Atenolol 100mg once daily Amoxicillin 250mg t.d.s. - Tell the patient what you mean be these times a day/ four times a day!

Contents of the Prescription 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

Sample Prescription-

Contents of the Prescription Indication Encouraged, seldom practiced Helps confirm appropriateness of medication Reminds patient of drug’s purpose Facilitates communication between health care providers

Prescription Formatting Heading Body Closing

Current Prescription Formatting Closing Prescriber’s signature Refill instructions Generic substitution instructions 5

Contents of the Prescription Refills To avoid interrupting maintenance therapy, practitioners can authorize refills on a written prescription Refills authorized are valid only for life of the prescription – 1 year

Controlled Substances Definition - a prescription drug whose use and distribution is tightly controlled because of its abuse potential or risk Regulation is more strict

Prescription for controlled drugs must(e.g.morphine) Be completely written in the prescriber’s hand writing in ink Be signed & dated Carry the prescribers’ address Carry the name & address of the patient State the form of the drug State the total quantity of the drug or the number of dose units to be disposed in both words & figures State the exact size of each dose in both words & figure.

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 200 mg instead of Vasotec 20 mg when a pharmacist misread this prescription

SUMMARY

MAXIMIZE PATIENT SAFETY ALWAYS write legibly. ALWAYS space out words and numbers to avoid confusion. ALWAYS complete medication orders. AVOID abbreviations. When in doubt, ask to verify.

Contents of the Prescription Date of the order Patient Name and Address Name of the drug Strength of the drug Quantity of the drug Directions for use Practitioner Name, Address, Telephone number

Model Prescription Name: ABC 2) Date: 31.07.07 3) Age: 70yrs. 4) Sex: male Diagnosis: Idiopathic Parkinsonism Rx 9) Tab Levodopa 100mg Tab Carbidopa 25mg 2 tablets by mouth 3 times daily for one month . Take with food. Dr. Sathya MD Assistant Prof. Neurology, Reg. No. 34523