Terra Sigillata

The other day I noted news of the Texas compounding pharmacy mistake that led to three deaths when an injectable colchicine preparation was found to be ten times more concentrated than labeled. Several readers commented on the reasons for the mistake, but I may have found another.

The source illustrating my pet peeve is the pharmacy’s own drug recall announcement posted this week on the FDA MedWatch site:

Recent deaths have been reported in connection with compounded Injectable Colchicine .5mg/ml, 4ml vials, lot number 20070122@26. As a result, ApothéCure is issuing an immediate drug recall at the request of the Texas State Board of Pharmacy for all strengths, sizes and lots of compounded Injectable Colchicine that we have sold in the last year.

Note specifically, “Injectable Colchicine .5mg/ml.”

The proper way to refer to fractional decimals less than one is with the leading zero: 0.5 mg/mL (or 0,5 mg/mL for my European colleagues).

Using “.5 mg/mL” just simply invites a ten-fold error. Is that decimal point a fleck on the prescription or the compounding instruction sheet (or computer screen)?

In that sense, it’s easy to see how the concentration could have been perceived as 5 mg/mL by the compounding pharmacist (especially if he/she shares my eyesight). It’s amazing to me that the unconventional use of “.5 mg/mL” even made it to the official recall notice that was them disseminated by the FDA.

Rick at Shrimp & Grits already noted that he would use this case to support why he does not give partial credit to his chemistry students for calculation errors. I wonder if Rick is also bothered by the lack of attention to including the leading zero?

I don’t treat patients so my calculation errors just end up wasting time. But I am still bothered when a new person in the lab makes up SDS-PAGE stacking gel buffer concentration and labels it .5M Tris-HCl, pH 6.8. I know that 5M is beyond the solubility of Tris, but please use “0.5M.” Maybe I’m finally just getting to be a cranky, old codger.

It’s finals time, students….doublecheck your calculations.

Comments

  1. #1 speedwell
    May 4, 2007

    When I was in elementary school and we discussed decimals, I was taught that the leading zero was wrong and my work got marked wrong when I used it. My engineer father had quite a talk with the teacher about that, but did not prevail. I don’t remember leading zeroes ever being discussed in high school or college, but I was not a math or science major.

    I asked a couple of kids I know (11 and 12) how they handle leading zeroes in their school. Only one of them had even seen it, and they both reacted like it was disgusting.

  2. #2 decrepitoldfool
    May 4, 2007

    “Maybe I’m finally just getting to be a cranky, old codger.”

    Maybe. But my father taught me “do it their way in school, but when you get out, do it right.” I use the leading zero today.

    The OpenOffice spreadsheet inserts the leading zero if you forget. I don’t know if Excel does.

  3. #3 Mark
    May 4, 2007

    The need for a leading zero is so obvious (for the reasons you mention) that I don’t see how anyone with the slightest sense could object to it, or forget it.

  4. #4 lazarou
    May 4, 2007

    0,5 mg/mL is for mainland Europeans only! This island-bound Euro is plenty happy with good old 0.5 thanks very much. Never could teach those barbarian mainlanders the difference between a full stop and a comma :-)

    100% behind you on the leading 0 though.

  5. I wonder if Rick is also bothered by the lack of attention to including the leading zero?

    That would be “yes”. Like I tell my students, that leading zero doesn’t have any real mathematical meaning, but it does have a reason for being there. It screams to anyone reading the number that there’s a decimal point coming up!

    I really do wonder if Apoth´┐ŻCure’s SOPs are as sloppy as their press releases? When I read the press release, I didn’t immediately see that decimal point.

    When I was in elementary school and we discussed decimals, I was taught that the leading zero was wrong and my work got marked wrong when I used it.

    Has that teacher has ever used a calculator, or read a decimal number in print? The leading zero is almost always there.

  6. #6 jim
    May 13, 2007

    IV colchicine use is restricted in Canada and requires Health Canada permission. I’ve been using it weekly for a refractory case of FMF, so this story is particularly scary. That little 0 may be more important for drugs rarely seen by the users.By the way, it’s 0.5 in English Canada, and 0,5 in French Canada.