Calculation help..

[garnetgirl29, BSN, RN]

Here's the problem:

Ordered: Morphine Sulfate 5 mg

Available: Morphine Sulfate gr.1/6 per mL.

Normally, I convert the fraction to a decimal because I don't like working with fractions, but this problem isn't working out for me either way. Can anyone help me figure this one? The answer key says 0.5 mL

[ChrissyRN74]

Are you forgetting to convert the grains to mg? 1grain=64.79891 mg

[HippieGypsyGirl]

That is correct. I convert the gr to mg. So I say there is 60mg/1gr so there are Xmg/.17gr (6/1=.166). That gives you 10 mg. Then do D/H*V. So 5/10*1=.5. Hope that helped. I am so bad at math but for some reason calculation clicked with me. Good Luck!

[Esme12, ASN, BSN, RN]

Nursing Math - Medical Dosage Equations Formulas Calculators Examples Solutions For Nurses

http://www.davesems.com/files/drug_dose_calculations.pdf

DosageHelp.com - Helping Nursing Students Learn Dosage Calculations

Medical Metric Conversion Tables and Dose Data

[TABLE]

[TR]

[TD=width: 136, align: right]1 pound (avoirdupois)[/TD]

[TD=width: 159]= 453.592 g [/TD]

[TD=width: 81, align: right]1/2 grain[/TD]

[TD=width: 100]= 30 mg[/TD]

[/TR]

[TR]

[TD=width: 136, align: right]1 pound (apothecary)[/TD]

[TD=width: 159]= 373.242 g [/TD]

[TD=width: 81, align: right]1/4 grain[/TD]

[TD=width: 100]= 15 mg[/TD]

[/TR]

[TR]

[TD=width: 136, align: right]1 ounce (avoirdupois)[/TD]

[TD=width: 159]= 28.35 g [/TD]

[TD=width: 81, align: right]1/8 grain[/TD]

[TD=width: 100]= 8 mg[/TD]

[/TR]

[TR]

[TD=width: 136, align: right]1 ounce (apothecary)[/TD]

[TD=width: 159]= 31.10 g [/TD]

[TD=width: 81, align: right]1/12 grain[/TD]

[TD=width: 100]= 5 mg[/TD]

[/TR]

[TR]

[TD=width: 136, align: right]15 grains[/TD]

[TD=width: 159]= 1 g [/TD]

[TD=width: 81, align: right]1/100 grain[/TD]

[TD=width: 100]= 600 mcg[/TD]

[/TR]

[TR]

[TD=width: 136, align: right]10 grains[/TD]

[TD=width: 159]= 600 mg[/TD]

[TD=width: 81, align: right]1/150 grain[/TD]

[TD=width: 100]= 400 mcg[/TD]

[/TR]

[TR]

[TD=width: 136, align: right]7 1/2 grains[/TD]

[TD=width: 159]= 500 mg[/TD]

[TD=width: 81, align: right]1/200 grain[/TD]

[TD=width: 100]= 300 mcg[/TD]

[/TR]

[TR]

[TD=width: 136, align: right]5 grains[/TD]

[TD=width: 159]= 300 mg [/TD]

[TD=width: 81, align: right]1/250 grain[/TD]

[TD=width: 100]= 250 mcg[/TD]

[/TR]

[TR]

[TD=width: 136, align: right]1 1/2 grains[/TD]

[TD=width: 159]= 100 mg [/TD]

[TD=width: 81, align: right]1/300 grain[/TD]

[TD=width: 100]= 200 mcg[/TD]

[/TR]

[TR]

[TD=width: 136, align: right]1 grain[/TD]

[TD=width: 159]= 64.79891 mg[/TD]

[TD=width: 81, align: right]1 kilogram[/TD]

[TD=width: 100]= 2.2 pounds[/TD]

[/TR]

[TR]

[TD=width: 136, align: right]1 pound[/TD]

[TD=width: 159]= 0.45 kilograms (kg) [/TD]

[TD=width: 81, align: right]1 stone[/TD]

[TD=width: 100]= 6.35 kg[/TD]

[/TR]

[TR]

[TD=width: 136, align: right]1000 mcg [/TD]

[TD=width: 159]= 300 to 7000 iu (below)[/TD]

[TD=width: 81, align: right]1000 mcg[/TD]

[TD=width: 100]= 1 mg[/TD]

[/TR]

[TR]

[TD=width: 136, align: right]1 scruple[/TD]

[TD=width: 159]= 1.2 g[/TD]

[TD=width: 81, align: right]1 drachm[/TD]

[TD=width: 100]= 28.8 g[/TD]

[/TR]

[/TABLE]

[MICPEricRN]

There are roughly 60mg in 1 grain. 1/6th of 1 grain would be 1/6th of 60mg 1/6 of 60 is 10. therefore, the concentration is 10mg/ml. For 5mg, you need half of that 10mg in 1ml, or 0.5ml.

And when are these nursing schools going to realize that no one uses grain, drams, minims, or avoirdupois ounces any more?

[garnetgirl29, BSN, RN]

Thank you so much!! That helped tremendously! I glide right through these calculations until they trip me up with that stupid apothecary system. I'm so glad it's not used much!