Converting Dosage Cups to Metric Dosing Could Prevent Death

Health care professionals should stop using dosing cups that measure in drams.

In a fatal event reported to the Institute of Safe Medication Practices (ISMP) National Medication Errors Reporting Program, a nurse misread the scale on a commonly used dosing cup as mL when measuring a dose of morphine sulfate oral solution 20 mg/mL for an opioid-naïve hospice patient.

Instead of administering 1 mL of the solution, the nurse administered 1 dram, or nearly 75 mg of morphine.

Incidents like this happen often enough that changes are being seriously considered. The ISMP noted a proposed change to USP <17> would require an appropriate dosing component, such as an oral syringe or dosing cup, include volume markings in metric units and on a single scale that corresponds with the dose instructions on the container label.

In the meantime, many health care facilities still use dosing devices with archaic measurement scales in drams, ounces, and household measurements. To avoid dosing errors, the ISMP recommends that health care professionals use oral syringes that measure in mL whenever possible. If a dosing cup must be used, it should measure in mL only, which some vendors can customize to achieve.

“Many health care professionals are familiar with mix-ups that have occurred when using dosing cups, sometimes causing serious medication errors,” the ISMP wrote in its national alert. “…Unfortunately, these cups are still available from major vendors, so it’s possible they will be found in your health care facility.”