HELP w/math prob????

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You are ordered to give Nitroglycerine gr 1/150. The pharmacy has supplied 0.4mg/tablet. How many tabs should you give?

I know that 1 gr = 60 mg (exception being Tyl)

Why am I drawing a blank on this problem? Thanks for any help!!

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You are ordered to give Nitroglycerine gr 1/150. The pharmacy has supplied 0.4mg/tablet. How many tabs should you give?

I know that 1 gr = 60 mg (exception being Tyl)

Why am I drawing a blank on this problem? Thanks for any help!!

60 divided by 0.4 = 150

The 0.4 mg tablet represents 1/150 of 60 (1 grain)

The 0.4 mg tablet represents 1/150 gr

do you agree?

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Specializes in Adult and Pediatric Vascular Access, Paramedic.

0.4 mg tab of NTG is equal to 1/150 grain

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Specializes in med/surg, telemetry, IV therapy, mgmt.
you are ordered to give nitroglycerine gr 1/150. the pharmacy has supplied 0.4mg/tablet. how many tabs should you give?

first of all, convert the dose desired of 1/150 grains into milligrams. this is a ratio (fraction) equivalency problem, thus:

1 grain/150 = x mg

you will solve for
x
by applying a conversion factor to convert the grains to milligrams. watch what i do with the left side of his equation:

1 grain/150
(dose desired)
x 60 mg/1 grain
(conversion factor)
=
0.4 mg

so, you now know that 1/150 grain is the same as 0.4 mg. your problem says that the pharmacy has supplied you with 0.4 mg tablets. since you now know that the dose ordered, in it's converted mg form is 0.4 mg, you will give
one tablet
. that is the answer.

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Specializes in being a Credible Source.

start by figuring how many grains in each tablet:

you're given that each tablet has 0.4 mg and you know that 1 grain is 60 mg. therefore:

[a] 0.4 mg/tab x 1 gr/60 mg = 0.4/60 gr/tab

now, clear the nasty decimal from the numerator (divide the numerator and the denominator by 0.4 each) :

0.4/60 gr/tab = (0.4/0.4) / (60/0.4) gr/tab = (1)/(60/0.4) gr/tab

[c] (1)/(60/0.4) gr/tab = (1)/(150) gr/tab

recognize in that:

  1. anything divided by itself = 1
  2. if you divide the numerator and the denominator by the same value (e.g. 0.4 in this case), you're not changing the value because you're essentially multiplying by 1.

recognize in [a] that:

  1. the units are consistent: mg/tab x gr/mg = gr/tab because the mg terms cancel.

(and now that i've posted i see that daytonite has beaten me to the punch :trout:)

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I found a link to a website with all of the apothecary conversions.

http://www.tostepharmd.net/pharm/clinical/measurement.html

Question? Has any nurse actually run into an order written in the apothecary system? I learned it to pass the class but will I ever have to use it?

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