Help! Math problem!!!!

[The Dude]

Can someone help me with the set-up for this math problem? I have my competency test (2nd year student) next week and this question is the only one that I can not figure out:banghead: Here it is:

Order: 0.5 mg Digoxin

The med book states only 60mcg/kg/day allowed.

How many mg less or more of the allowed dose are you off?

The child weighs 22lbs.

ANSWER (per the answer key without any description of set-up):

0.1 mg LESS

Thank you for the help!!!!!

[Daytonite, BSN, RN]

order: 0.5 mg digoxin

the med book states only 60mcg/kg/day allowed.

how many mg less or more of the allowed dose are you off?

the child weighs 22lbs.

i come up with. . .

60 mcg/kg

(dose desired)

x 22 pounds/0.5 mg

(desired dose for 22 pound child)

x 1 mg/1000 mcg

(conversion factor)

x 1 kg/2.2 pounds

(conversion factor)

=

1.2

dose which depending on the form of the drug supplied would probably need to be rounded down to 1 of whatever is supplied. because the figures going into the problem involve a 0.5, it would be customary to express the final answer as

0.1

. that is just the correct protocol for significant figures for these things and that is why your answer was given as 0.1 and rounded off.

[The Dude]

Thank you!! I just could not get my math set up to work out, even after I looked at the answer given!

[tiggerdagibit]

I got the same answer, but in a different way....

First make all conversions:

0.5 mg x 1000 = 500 mcg (I just move the decimal 3 places)

22 lbs/ 2.2 = 10 kg

60mcg x 10kg = 600 mcg allowed per day

600mcg allowed - 500mcg ordered = 100 mcg difference

100 mcg = 0.1 mg less

[BeeBeeRN]

60mcg/kg-day x 1mg/1000mcg x 22 lbs/1 x 1kg/2.2 lbs = 1320/2200 = 0.6 mg

0.6mg - 0.5mg = 0.1