Calculation question (involving reconstitution)

[AshMariee]

[color=#ff0066]okay, so i'm studying for a pharmacology test for monday march 26, 2012. i am having a very hard time with calculations. one of my practice questions is:

a client has just delivered an 8lb 8oz baby boy after prolonged labor. the pediatrician orders ampicillian 50mg to be given by the intramuscular route to the newborn every 8 hours. the nurse is initiating the first dose. ampicillian is available in powder form for injection. the directions on the bottle indicate reconstitution with 0.9 ml of sterile diluent for a concentration of 125mg/ml. how many ml would the nurse prepare to administer the first dose?

i actually don't even really understand the question, let alone a formula for how to solve it. please help!!!

[Esme12, ASN, BSN, RN]

look here at these sites and you will find the easy solution.

dosagehelp.com - helping nursing students learn dosage calculations - dosage question steps

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

dosagehelp.com - helping nursing students learn dosage calculations - mass/liquid for liquid questions

example: ordered lasix 40 mg iv push now. available: 80 mg in 1 ml. how much will the nurse draw up?

[table=class: example]

[tr]

[td][table=class: fraction]

[tr]

[td=class: numerator]ordered[/td]

[/tr]

[tr]

[td=class: denominator]have[/td]

[/tr]

[/table]

[/td]

[td] x volume per have[/td]

[td] = y (liquid required)[/td]

[/tr]

[/table]

[table=class: example]

[tr]

[td][table=class: fraction]

[tr]

[td=class: numerator]40 mg[/td]

[/tr]

[tr]

[td=class: denominator]80 mg[/td]

[/tr]

[/table]

[/td]

[td] x 1 ml[/td]

[td] = 0.5 ml[/td]

[/tr]

[/table]

[rn.d86]

The only information you need to know is how much you are looking to give (50mg) and what you have (125mg/1ml). I was taught to use the formula desire/have x supply. I'll let you figure out how to set it up and see if you can get the correct answer.

My advice is that you should not get too concerned with the information that you do not need to know.

[Sun0408, ASN, RN]

Esme is so great with helping students and nurses alike. Love the links she provides :)

[loriangel14, RN]

I use the formula doc( what the doc ordered) over stock(what you have on hand). or 50/125. 50 divided by 125 is 0.4.

You would give 0.4mls.

Which part of the question did you not understand?

[alemieux1]

[color=#ff0066]okay, so i'm studying for a pharmacology test for monday march 26, 2012. i am having a very hard time with calculations. one of my practice questions is:

a client has just delivered an 8lb 8oz baby boy after prolonged labor. the pediatrician orders ampicillian 50mg to be given by the intramuscular route to the newborn every 8 hours. the nurse is initiating the first dose. ampicillian is available in powder form for injection. the directions on the bottle indicate reconstitution with 0.9 ml of sterile diluent for a concentration of 125mg/ml. how many ml would the nurse prepare to administer the first dose?

i actually don't even really understand the question, let alone a formula for how to solve it. please help!!!

i also got 0.4 ml. the question can seem complicated if you pay attention to unneeded information. the question already states that the pediatrician ordered 50mg. this is what you start with, as it is the ordered dose. since the ampicilian is in powder form, you need to dilute the solution (0.9 ml dilutent for the concentration of the ampicillian available: 125mg/ml. so you set up the problem by starting with 50mg, set up a cancellation/equivalants problem: 50mg divided by 125 mg divided by 0.9 ml=approx. 0.4 ml. the information about the weight of the baby is not needed in the equation, since the ordered dose amount is already indicated. hope this helps, good luck!