# dosage calculation

Published

• Has 1 years experience.

Hello All,

I was hoping for some help!! =)

Here is the question

A magnesium sulfate solution 0.2 ml/kg body mass is prescribed by a physician. How many ml will a 160 lb. patient recieve?

Thanks in advance for any help!!:typing

217 Posts

.2 ml 1kg 160lbs

----- x ----- x ----- = 14.54 mL

1 kg 2.2 lbs 1

Dimensional analysis is easier on paper

=| It refuses to keep the formatting when I edit

890 Posts

Hello All,

I was hoping for some help!! =)

Here is the question

A magnesium sulfate solution 0.2 ml/kg body mass is prescribed by a physician. How many ml will a 160 lb. patient recieve?

Thanks in advance for any help!!:typing

Convert: 160lbs / 2.2kg = 72.7kg

Multiply: 72.7kg x0.2mL=14.54mL

1 Article; 2,396 Posts

Specializes in Ortho, Neuro, Detox, Tele.

correct...160lbs/ 2.2 lbs per kg...cancel the lbs, and you get 72.7 kg, multiply that by 0.2 ml/kg..the kg cancel, and you get 14.54 mL....BUT you're not done, you have to round that to 14.5 mL..else you'll probably be wrong..mL calcs are usually done only to the tenths on the final answers...

63 Posts

unless you are taking your nursing at Los Angeles County School of Nursing & then, god help you if you round...you may end up failing the Drug Dosage Calculation exam that you have to take every semester...

29 Posts

Has 1 years experience.

Thanks to all that replied!!

237 Posts

Okay guys on this, I keep messing this up, I do

2.2lbs/1 kg = x/160lbs so that I have 2.2lbs on top on the right hand side and 160lbs on the bottom of the left hand side so I can cross of the lbs. So this gives me 2.2 % 160= and not 160 % 2.2 which I know gives the right answer. I keep setting it up wrong, can anyone explain this to me?

784 Posts

Specializes in Utilization Management. Has 12 years experience.

"2.2lbs/1 kg = x/160lbs so that I have 2.2lbs on top on the right hand side and 160lbs on the bottom of the left hand side so I can cross of the lbs. So this gives me 2.2 % 160= and not 160 % 2.2 which I know gives the right answer. I keep setting it up wrong, can anyone explain this to me?"

It would be 2.2lbs/1 kg = 160lbs/x kg....the way you were setting it up would have you multiplying 2.2lbs by 160lbs...you want to divide 160lbs by 2.2lbs in order to find out how many kg are in 160lbs.

2.2lbs / 1 kg = 160lbs / x kg

2.2x = 160

x = 72.73 kg rounding per your school's instructions of course

237 Posts

Thank you, I see what your saying. I guess I have to get multiplying and dividing straight! Geez, what's that 3rd grade math I can't even manage? Oh brother, it's gonna be a looooooong 2 years! Thank you for explaining that to me.

784 Posts

Specializes in Utilization Management. Has 12 years experience.

LOL it becomes second nature after a while. Good luck!

3 Posts

Hi my math is rusty but i hope it helps to know that you convert the lbs to kg and multiply the kg by the 0.2 I got 14.5 good luck!!!

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