Error Number 34. Mistaking the dram symbol for "oz"

A doctor wrote this order for a patient who had spastic colon:

During medication rounds, the patient's nurse mistook the dram symbol for "oz" and gave the patient 30 ml of Donnatal Elixir-a combination of belladonna alkaloids and phenobarbital. This was about six times the usual dose.

When the patient developed an anticholinergic reaction, the nurse checked the order with the doctor and discovered her mistake. Luckily, the patient wasn't harmed by the overdose.

As this error illustrates, apothecary symbols are frequently misinterpreted or used incorrectly. Because using these symbols can lead to errors, hospitals have all but eliminated apothecary symbols in orders. If a doctor prefers to write orders with apothecary symbols, the hospital should convince the doctor that using metric measures prevents confusion ... and errors.