We need to go metric to prevent errors with oral liquids
Nothing riles me more than when a report reaches us through our medication error reporting program where a child accidentally gets an overdose of liquid medication due to nothing more than simple confusion between dosage units. Doctors, pharmacists and parents mix up teaspoons and tablespoons, milliliters and teaspoons, or drops and mL, a metric measure of volume. This is one error that should not be happening at all. We know what's needed to put an end to it.
We need to go metric to prevent errors with oral liquids
Michael Cohen
Nothing riles me more than when a report reaches us through our medication error reporting program where a child accidentally gets an overdose of liquid medication due to nothing more than simple confusion between dosage units. Doctors, pharmacists and parents mix up teaspoons and tablespoons, milliliters and teaspoons, or drops and mL, a metric measure of volume. This is one error that should not be happening at all. We know what’s needed to put an end to it.
In June I wrote about a pharmacist’s labeling error that gave instructions for a young child to receive 3.5 teaspoonfuls a day of antibiotic liquid instead of 3.5 mL that the doctor had ordered. The child experienced voluminous amounts of diarrhea, a yeast infection, and possibly a fungal infection of the vaginal area. In that same article I described how my own wife, a seasoned RN who works with me on medication safety efforts, misread the readings on a liquid dosage cup. She read TBSP (tablespoonful) as TSP (teaspoonful) and gave our granddaughter Sydney 2 tablespoonfuls of Tylenol liquid instead of 2 teaspoonfuls. Fortunately, we caught the error before the next dose and things turned out fine.
I get annoyed about the whole situation because we first reported on the confusion of teaspoonfuls and mL in 2000. In 2009 we issued a call for practitioners to move to sole use of the metric system (mL) for measuring over‐the-counter (OTC) and prescription oral liquid doses. But mix‐ups continue to cause serious injury in children and adults. ISMP has received more than 50 reports of mL‐teaspoonful errors alone, including cases where injuries required treatment or hospitalization.
Why did we call for sole use of the metric system anyway? One reason is that dosage strengths of medicines use the metric system. For example, an oral liquid antibiotic might be labeled 125 mg per 5 mL. Syringes and dosing cups that come with oral liquids also are labeled in mL. Also, dosage calculations are made using metric weight in kilograms and mg or mL.
With medicines, accuracy is obviously important. An accurate teaspoon should hold 5 mL. But household spoons are not standardized and deliver only an approximate dose at best. Depending on their size, a typical household teaspoon can hold between 3 and 7 milliliters (mL). One mL is about 1/30th of an ounce. So if the doctor wants the patient to have 125 mg three times a day, the prescription directions should state, “Five mL three times a day.”
My organization, the Institute for Safe Medication Practices (ISMP), is once again asking prescribers, pharmacists, other healthcare professionals, manufacturers and computer system vendors to only use metric measurements in prescription directions. Our board of trustees took this step after careful deliberation, in order to better protect patients from harmful errors. It also gives providers a greater level of comfort and confidence when calculating and administering doses of medication.
Other organizations, such as the US Food and Drug Administration, Consumer Healthcare Products Association, and Centers for Disease Control and Prevention have also drawn attention to use of the metric system for oral liquids or suggest including both measurements with drug dosing instructions. We’ve met with each of these groups to stress that use of the metric system alone when prescribing, dispensing, and administering medications would prevent mix‐ups because there would only be one method used to communicate and measure doses.
I have often heard my pharmacist colleagues express doubts about getting consumers to go completely metric for measurement of medicine doses. However, I don’t think it’s a stretch at all. Several companies, including McNeil Consumer Healthcare, are already moving in this direction by standardizing their acetaminophen infant and children’s oral liquid medications in a single concentration and developing dosing devices that measure in mL. Many other companies are following suit. I have no doubt that you’ll be able to do your part.
We are also asking pharmacists to take steps to ensure patients have an appropriate device to measure oral liquid volumes in milliliters. They’ll need to coach patients on how to use and clean measuring devices and have patients show them they know how to measure by asking them to demonstrate their understanding.
We realize that a transition period may be necessary during which the household measure can be listed in parentheses immediately following the metric measure—e.g., 5 mL (one teaspoonful). But still, it’s time that authorities set a date for full conversion. Solving this common reason for medicine overdoses in children should be the goal for all of us. I’d love to hear from you about your thoughts on the matter.
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BS! The simple fact is that our schools don't teach metric, so the vast majority of americans don't have a clue on what ml means. Heck they can't even do a pint to quart conversion, much less read a ruler. Sounds like a solution looking for a problem.— jimmymack- Thanks for writing jimmymack. I appreciate hearing your opinion. One of the most important ways that highly reliable organizations prevent errors is to standardize the way things are done. That way everyone is working on the same page and confusion is reduced. That's exactly what industry, FDA, CDC and ISMP are doing here. In this case, use of mL for liquids will prevent mix‐ups because there would only be one method used to communicate and measure doses. As I said in the blog, I have no doubt at all that consumers will know how to use measuring devices because they are already labeled in mL. So if 5 mL is prescribed, that amount is right on the cup. We are advocating a transition period where both mL and teaspoon would be side-by-side on the cup. No doubt this will take some getting used to but again, it's important that everyone agree to a standard - companies, doctors, pharmacists, nurses and patients/caregivers. The idea is for dosing instructions and measurement to be in mL so that teaspoons doesn't even enter the thought process and result in accidentally writing 4 teaspoons instead of 4 mL for a child with kidney disease. That was the subject of a report we received just today. I hope others will chime in. Mike— ismp1
- Mike, can't agree with you more - all measurements regarding drug dosing should be expressed using the metric system, period. I, however, think dosing cups are innacurate at best and lethal at worst. Many dosing cups provide for too large a dosing range, hard to visualize the gradations and subsequent measurement of a correct dose and to the untrained....isn't a full cup the proper dose? Then of course there is the tbsp vs. tsp confusion even where mls are also displayed.
We have to move away from using common household terms and utensils for measuring drug doses. Within that same light however, we need to standardize and provide consistency in available dosing instruments....as these range all over the board. I personally would like to see the standard being oral syringes with universally fitting bottle adapters. It is then incumbent on the pharmacist to train patients on how to use the product correctly. This interaction would provide for even those with low health literacy to 'get it'. The caveat - those with physical disabilities that could not manipulate the device. The solution would be for the pharmacy to prepack the required number of doses for the patient but there are issues with that as well...and so it goes.
I appreciate the dedication and continued efforts of ISMP to improve the safety of our medication sytem and practices.— janrx1215 - ISMP is absolutely correct. Having a single standard for ANY measurement is important and is even more critical for medicines. Pun intended, the canard that "schools don't teach 'metric' [sic]" simply doesn't fly. Using multiple and confusing units AND requiring people to translate them is simply a recipe for disaster. If the medicine is measured only in mL and the dosage item is measured only the same way there would be far fewer chances of a mix-up.
While we're at it, as a person with years of scientific and technical experience I can say that the problem extends far beyond medicine. The fact that the US is the only country stubbornly clinging to the old English measurement system adds enormous hidden costs to our economy. By some serious estimates mistakes in converting not only between English and metric units, but among English units alone, plus lost trade due to incompatible manufacturing standards, result in losses of as much as $100 -billion- per year. Whether we like it or not, the rest of the world is metric. We should have joined decades ago.
— JeffK
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