13 October 2009

This is why we have SI

I have a bottle of a nasal spray that I'm using for allergies, and it says on the label that each spray delivers "50 mcg" of the drug. What in the world is a "mcg"? Do you think they mean μg (microgram), which is 10-6grams, or in SI units a single spray would be delivering 5*10-8kg of drug, or do you think they mean m-c-g (milli-centi-grams), which would be 10-3*10-2grams =10-5grams, or in SI units a single spray would be delivering 5*10-7kg? These are two different values depending upon how I read the label, one of which is the actual amount of drug delivered and the other of which is either 10 times or one tenth the amount of drug delivered.

This is the whole reason we have metric prefixes in the first place, to reduce confusion and have a standard system whose meaning everyone agrees to. Good thing the actual quantity of the drug here doesn't matter to me, I just take my prescribed two sprays.

26 comments:

RoxBlog said...

Interesting site. I have one similar. Try it Fair Science bye.

Jordan Atlas said...

mcg is microgram, and it's only written this way in pharmacy/medical contexts as far as I know.

I think they do it like that to avoid confusion between mg (miligram) and μg (microgram), which can be easily confused in handwriting (and many prescriptions are handwritten). So they want the label to match what the prescription says.

Term said...

Great piece of work thanks for increasing my knowledge wait for your next post..!

DK said...

Are they allowed to sell it that way?

It doesn't matter that it's only used in a medical context. People should know what they get into their nose :)

Jordan Atlas said...

Well, sure, people should know what they get into their noses. But I think in the medical context the priority is that people get an effective and safe dose.

Anonymous said...

Nice Blog, SI units help us to measure the quantity accurately. Before SI units the rough measurement tools were used like sand glass, elbow and palm to measure quantity.
I am preparing my CBSE Board Exam and i like science a lot i have a keen interest to do practicals.

Audrey Damara said...

nice post, mate.

R2K said...
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Ilmu Pengetahuan said...

Cool explanation and nice blog.

Thoughts Unleashed said...

nice!
at least someone is trying to know how much dose of medicine he is taking.. most of us ignore these things..

James Taylor said...

Sometimes Science relates to Math. By the way, I have a spreadsheet here if you have few things to share kindly check it out:) Thanks in advance! https://spreadsheets.google.com/viewform?hl=en&formkey=dEhjUThVaUJQbmFBeV9oajFVTDZmbFE6MA#gid=0

cv said...

Thanks for this wonderful discovery..at first i was also confused with mcg! later researched online and got to know of this..anyways thanks for sharing this with me!


Computer Science CV

ETACM said...

It is incredible how little of what we use every day we understand. Most people wouldn't think twice about that!

ShrikeNo1 said...

Unfortunately, most of the people don't know SI units. And talk about mili, micro, nano, pico... Hm, what's that...

Ecommerce website developer said...

Yes, I too agree with you that we have metric prefixes in the first place, to reduce confusion and have a standard system whose meaning everyone agrees to. This article has doubled my knowledge. Thanks you!

Chalky said...

They may avoid one confusion, but only at the expense of another. Time for doctors to improve their handwriting!

Eknan said...

I don't understand the purpose of having a "standard" and a metric measurement system. It would cost multiple million dollars to reprint and teach students to understand it, but since when has America had much concern about spending?

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Blue Mountain Travels and Tours pvt. Ltd. said...
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Amitash said...

Yes. mcg is microgram becuase (mu) cannot be understood by common public.

Microbiology Scientist said...

Modern physics changed because of Neutrino exceed the speed of light. Can't we you this new theories to excavate new things in universe?

qqq said...

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Brad maddox said...
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