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Hospitals Warned About Dual Measurements on Oral Dosing Devices

HORSHAM, PA – It’s time to replace the outdated dosing cups that your hospital may still be using.

That’s according to an alert from the Institute of Safe Medication Practice’s National Medication Errors Reporting Program. The ISMP reported a patient death after a nurse confused two dosing scales that appear on an oral liquid dosing cup, mistaking fluid drams for milliliters.

“Unfortunately, these cups are still available from major vendors, so it’s possible they will be found in your healthcare facility,” according to the alert. “In their place, available oral syringes that measure only in mL should be used to measure doses of oral liquid medications whenever possible. If a dosing cup must be used, ideally it should allow measurement in mL only.”

ISMP points out that, while the cups “are not widely available at this time, some suppliers can customize dosing cups to measure in mL only.” If hospitals can’t get a customized cup, they may still have to use those with the dual mL and household measurements until mL-only cups can be supplied, the group concedes.

“Make sure your purchasing group or department knows what type of cup to purchase,” the alert adds. “Also, only purchase dosing cups that have printed, rather than embossed, measurement scales, so they are easier to read.”

In the fatal event cited in the alert, a nurse measured a dose of morphine sulfate oral solution 20 mg/mL incorrectly for an opioid-naïve hospice patient, misreading the scale marked drams as mL and administering 1 dram of the medication instead of 1 mL. One dram is equivalent to 3.7 mL, so the patient received close to 75 mg of morphine.

In a second case described by the alert, a nurse gave a patient 5 drams of a formerly available acetaminophen liquid concentrate, 100 mg/mL, instead of 5 mL, a total of 18.45 mL, or 1.845 g of acetaminophen.

“While progress is being made in hospitals in regards to prescribing liquids in mL, many hospitals still use dosing devices that have household measures (e.g., tea spoonful, dessertspoonful, tablespoonful) and, as above, even drams and ounces,” according to the ISMP. “This sets healthcare professionals up to fail because the dosage scales on embossed cups are difficult to read, have dangerous abbreviations that are easily confused (e.g., TBS and TSP), and measures that are no longer used (e.g., drams).

Drams and ounces, which also appear on these cups, are from an outdated apothecary no longer in clinical use.

A proposed change from United States Pharmacopeia, endorsed by government agencies and a number of medical and pharmaceutical associations, requires that gradations on dosing devices “shall be legible and indelible, and the associated volume markings shall be in metric units and limited to a single measurement scale that corresponds with the dose instructions on the prescription container label.”