# Dosage Calculation Questions

Published

Can someone please help me with the following two problems. I have tried several times to work them and cannot come up with the answer that is correct:

Tylenol Elixir grV is ordered. The bottle reads 25 mg/cc. How much should the nurse administer? The answer is 12 ccs, but I can't figure out how to get that number.

A vial contains 2 GM of powder. After being reconstituted with 4 cc saline, how many mls are needed to administer a 500 mg dose? The answer is 1 cc, but again, can't figure out how to arrive at that.

I'm sure I'm not setting up the problems correctly.

Any help would be greatly appreciated!!! I'm doing this as a review for a dosage calculation test and I need to know how to set these up.

4,220 Posts

tylenol elixir grv is ordered. the bottle reads 25 mg/cc. how much should the nurse administer? the answer is 12 ccs, but i can't figure out how to get that number.

the first thing you need to do is convert grains to mg. 1 grain consists of 60 mg (some references state 65). so, you can solve this using ratio : proportion.

x : 5 = 60: 1

x = 300

next, use d /h x q to determine how many ml you need. d = the dose ordered; h = the quantity on hand, and q = the total volume of the quantity on hand

x = 325 / 25 x 1

x = 12

a vial contains 2 gm of powder. after being reconstituted with 4 cc saline, how many mls are needed to administer a 500 mg dose? the answer is 1 cc, but again, can't figure out how to arrive at that.

first, you need to convert g to mg, then you can use d/h x q to solve this problem as well.

x = 500 / 2000 x 4

x = 0.25 x 4

x = 1

hope this helps.

1,171 Posts

Specializes in L&D/Maternity nursing.

Tylenol Elixir grV is ordered. The bottle reads 25 mg/cc. How much should the nurse administer? The answer is 12 ccs, but I can't figure out how to get that number.

on hand: 25mg/cc

ordered: gr 5---> 60mg=gr---> 5x60=300mg ordered

I do ratio and proportion to figure the dosage calculations out

25mg/cc=300mg/Xcc, solve for X (cross multiply)

300=25x

x=12 cc

A vial contains 2 GM of powder. After being reconstituted with 4 cc saline, how many mls are needed to administer a 500 mg dose? The answer is 1 cc, but again, can't figure out how to arrive at that.

does 2 GM mean 2 grams? Thats what I am assuming. Anyways, 2 grams=2000mg (1000mg to 1 g)

on hand: 2000mg/4cc

ordered: 500mg

ratio and portion again:

2000mg/4cc=500mg/Xcc, solve for X (cross multiply)

4(500)=2000X

2000=2000X

x=1 cc

1 Article; 14,603 Posts

Specializes in med/surg, telemetry, IV therapy, mgmt.

tylenol elixir grv is ordered. the bottle reads 25 mg/cc. how much should the nurse administer? the answer is 12 ccs.

dose desired:
tylenol elixir grain v (5)

dose on hand:
tylenol elixir 25 mg/cc

amount the dose on hand comes in:
1 cc

conversion factor:
1 grain = 60 mg

by dimensional analysis (factor label) method:
5 grains
(dose desired)
/25 mg
(dose on hand)
x 1 cc
(amount the dose on hand comes in)
/1 x 60 mg/1 grain
(conversion factor)
=
12 cc

if you do the conversion first (5 grains = 300 mg), the problem simply becomes:

300 mg
(dose desired)
/ 25 mg
(dose on hand)
x 1 cc
(amount the dose on hand comes in)
=
12 cc

a vial contains 2 gm of powder. after being reconstituted with 4 cc saline, how many mls are needed to administer a 500 mg dose? the answer is 1 cc.

dose desired:
500 mg

dose on hand:
2 grams

amount the dose on hand comes in:
4 cc

conversion factor:
1 gram = 1000 mg

by dimensional analysis (factor label) method: 500 mg (dose desired)
/2 grams
(dose on hand)
x 4 cc
(amount the dose on hand comes in)
/1 x 1 gram/1000 mg
(conversion factor)
=
1 cc

if you do the conversion first (2 grams = 2000 mg), the problem simply becomes:

500 mg
(dose desired)
/2000 mg
(dose on hand)
x 4 cc
(amount the dose on hand comes in)
=
1 cc

1,446 Posts

Specializes in ED, ICU, PACU.

A vial contains 2 GM of powder. After being reconstituted with 4 cc saline, how many mls are needed to administer a 500 mg dose? The answer is 1 cc, but again, can't figure out how to arrive at that.

Don't know if you would be interested in trying to solve this a less mathematical and more verbal way; but, I suspect you are getting hung up on the math to the point you are having difficulty thinking it through.

So, for the above question look at it this way:

The vial contains 2GM of powder & you need to administer 500mg dose; so, 2 GM is the same as 2000mg (converting that to what is asked for in the dose to be given).

Next, looking at the liquid portion, you have 4 cc. The 4 cc in that vial will hold the 2000mg, after being reconstituted.

So, now you will have 2000mg of powder floating around in that 4cc of saline.

Got to administer 500mg dose. But, the full vial of 4cc has 2000mg. 1/2 of that vial is 2cc & 1/2 of the powder floating would be 1000mg. But, you need to give 500mg---and, that wouldn't be 1/2 (1000mg in 2cc), it WOULD be 1/4 of that.

1/4 of 2000mg is 500mg & 1/4 of 4cc would be 1cc.

So, to give the dose of 500mg you would have to draw up and administer 1cc (1/4 of the 2000mg floating around in the 4cc of saline). Try to visualize it.

By using the site, you agree with our Policies. X