Prescription Writing: The Errors That Actually Reach Patients

Interns write the majority of inpatient prescriptions and, unsurprisingly, make the majority of prescribing errors. The reassuring part is that the errors are not exotic. They cluster into a small number of recurring patterns, and knowing the patterns is most of the defence.

At a glance

How numbers get misread

A decimal point is a small mark on a photocopied, faxed or hurriedly-read chart. Two conventions exist because of this.

First, never write a trailing zero after a decimal point. If the point is missed, the number reads ten times larger than intended. Second, always write a leading zero before a decimal point for doses less than one, so that the point is anchored and cannot be overlooked.

Where a dose can be expressed without a decimal at all by choosing the appropriate unit, do that instead. Whole numbers cannot be misread.

Abbreviations

Abbreviations for units are a recognised, repeatedly documented source of error, because several of them look alike in handwriting and several look like numbers. Write units in full. The same applies to drug names — abbreviations for long drug names are ambiguous when more than one drug shares a prefix, and several do.

Frequency abbreviations vary between the traditions people were trained in, and the same abbreviation does not always mean the same thing to everyone reading it. Writing the frequency out removes the ambiguity entirely at a cost of a few seconds.

Before you write anything

1. Confirm the patient’s identity against the chart.
2. Check and record allergy status, including what actually happened. “Allergic to penicillin” that turns out to have been childhood nausea is a very different clinical situation from anaphylaxis, and the distinction changes what can safely be prescribed.
3. Review the complete current medication list, including anything the patient takes at home, over the counter, or herbal. Duplication and interaction are found here or not at all.
4. Consider renal and hepatic function, since both change how a drug is handled.
5. Consider pregnancy and breastfeeding where relevant, and ask rather than assume.
6. Check the indication is documented. A drug with no recorded reason tends to survive discharge and follow the patient for years.

What a complete prescription contains

• Patient identifiers
• Drug name written in full, generic unless there is a specific reason not to
• Dose, with units written out
• Route
• Frequency, written out
• Start date, and where applicable a stop date or review date
• Your signature and a legible printed name, plus a way to contact you

The stop or review date deserves emphasis. Antibiotics, sedatives and analgesics prescribed without one are the drugs that quietly continue long past their usefulness.

Common prescribing errors and how to avoid them

Working with the pharmacist

A pharmacist querying your prescription is the system working, not a criticism. They catch a substantial proportion of errors before they reach the patient. The useful posture is to answer the question directly and to ask what prompted it, because the answer is usually something worth knowing.

Last-minute checklist

• Allergy status checked and recorded, with the nature of the reaction
• Full medication list reviewed, including home and over-the-counter drugs
• Renal and hepatic function considered
• Generic name, written in full
• No trailing zero; leading zero present; whole numbers where possible
• Units and frequency written out, not abbreviated
• Indication documented; stop or review date set
• Signed, printed, contactable

References

• Your current national formulary
• Your hospital’s prescribing and medicines reconciliation policy
• Local antimicrobial prescribing guidance