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Study: Switching to metric system could reduce medication errors

Special to The Forum

FARGO – Put down the teaspoons, parents – there’s a good chance you’re not measuring correctly.

Adding a little too much vanilla when following a recipe might result in a batch of bad cookies. But a mistake when pouring liquid medication can cause significant health problems, according to a recent study that suggests kids would be better off if their parents dropped the teaspoon in favor of the metric system’s milliliter.

The study, published July 14 by the American Academy of Pediatrics, aimed to see if the measurement unit used by parents would affect the error rate.

About 40 percent of the 287 parents of children given liquid medication prescriptions in emergency rooms who were tracked by researchers incorrectly measured the dose, and they had twice the odds of making an error compared to those who used milliliter-only dosages.

Another problem, the study found, is 16.7 percent of parents used a nonstandard device. Rather than using a dosage cup or teaspoon, some grabbed a spoon out of the silverware drawer, mistakenly believing it was the same amount – though a larger spoon might be a tablespoon, which is 3 teaspoons and triple the intended dosage.

That’s why students in North Dakota State University’s pharmacy program are taught comparable units between the so-called English system used in America and the metric system, according to Alicia Fitz, an assistant professor of pharmacy practice and pharmacist at the school’s Student Health Service.

While pharmacists have the power to add to or clarify directions on a label – for example, they can include the equivalent dosage in milliliters – the unit of measurement of the original prescription is up to the doctor, she said.

“You will see prescribers write for a teaspoon and you will see prescribers write for it in milliliters, and you will sometimes see a combination of both,” she said. “So, you kind of have to decipher it.”

Still, Dogan Comez, a mathematics professor at NDSU, said the problem ultimately comes down to America’s refusal to drop the English system that has lost favor around the world. The only other countries still on the English system of teaspoons, miles and pounds are Myanmar and Liberia.

“Even the originating country, they switched to the metric system and we are still sticking to it,” he said. “That’s another irony about the whole story.”

Complicated math

The metric system is “very, very methodical,” Comez said, which makes it easy to use. For example, the standard unit of length is the meter, 1/100th of a meter is a centimeter and 1/1,000th of a meter is a millimeter. That means converting from meters to millimeters simply requires moving the decimal point a few places.

That’s not the case with the English system, which is no longer used in England and has evolved into the form now used in the U.S. over hundreds of years.

While the standard unit of length is the foot, the next smallest unit is the inch, or 1/12th of a foot, and there’s nothing smaller than that. That means a small measurement might be three-quarters of an inch, which is 1/12th of a foot, and the mental math gets tricky.

That same complexity applies to liquid measurements, and that’s why parents make so many mistakes.

The teaspoon is one-third of a tablespoon; 16 tablespoons is 1 cup; 2 cups equals 1 pint; 2 pints is 1 quart; and 4 quarts, or 128 fluid ounces, make 1 gallon.

If a parent needs to make a dosage conversion, Comez said, they have to crunch the numbers and sort through fractions – and many will mix it up.

“People make more mistakes when it comes to fractions,” he said. “It’s a natural tendency, especially for some people who are mathematically challenged.”

The likelihood of problems has been pointed out before. The Institute for Safe Medication Practices, the U.S. Food and Drug Administration and the Centers for Disease Control and Prevention have all warned of the hazards of not making the metric switch in the medical community.

Pharmacists can help cut the odds of making a mistake, according to Fitz, especially if they include a proper device for the medication, such as a teaspoon, dosing cup or a syringe.

Still, she said it’s important to show every patient or parent how to properly read the measurement markings on these devices – and remind them that they can’t just use a kitchen spoon instead.

“Even for a really highly educated person, it’s been shown that as you’re busy and as you’re looking at something quickly, you might not be as careful or looking into it as much,” she said. “They might not have that conversion down themselves. So if you don’t teach them or explain that to them thoroughly, it could be something anyone could do at any health literacy level.”

Ultimately, the only advantage of sticking with the English system is its familiarity among the general public in America, Fitz said.

Comez, too, said there’s “absolutely no logic whatsoever” from a mathematical perspective. As it leads to dosing problems, and raises the potential for errors in other sectors, he said it makes sense f to embrace the more logical metric system like other countries have done.

“They are using the metric system like the rest of the world, and I think it is time for us to do the same,” he said.

Ryan Johnson

Ryan Johnson has been a Forum reporter since 2012 and previously wrote for the Grand Forks Herald.

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