# Help RN's w/ my HW!

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Hi I am currently taking pharmacology 100 and we are doing dosage/calculations in this class and there is a problem I cannot figure out can you help.

Q:A dose of 450mg of penecillin has been ordered. The drug comes as 25mg/mL. What volume of solution is needed to obtain the correct dose?

A: First, I think you have to covert the 450mg to mcg right? then you can use the formula...which he wants us to use the basic formula method...D/OH TIMES Q +X....???PLZ HELLP !!!

Specializes in forensic psych, corrections.

Are you serious? Why would you convert to mcg? Divide 25 mg into 450 mg and you'll have the necessary volume. I'm quite sure you can manage this yourself.

Specializes in Oncology/Haemetology/HIV.

Why would you convert to mcgs?

Please show us your work thus far, and perhaps we can redirect you.

Specializes in Wound Care, LTC, Sub-Acute, Vents.
hi i am currently taking pharmacology 100 and we are doing dosage/calculations in this class and there is a problem i cannot figure out can you help.

q:a dose of 450mg of penecillin has been ordered. the drug comes as 25mg/ml. what volume of solution is needed to obtain the correct dose?

a: first, i think you have to covert the 450mg to mcg right? then you can use the formula...which he wants us to use the basic formula method...d/oh times q +x....???plz hellp !!!

did you find out the answer? if not, here is my solution. you can use cross multiply and solve for x (which is the answer).

first set up the solution like this:

25 mg/1 ml = 450 mg / x

now, you can cross multiply:

25 mg x (25 mg x x) = 450 mg ml (450 mg x 1 ml)

so now you want to divide both sides with 25 mg so you can have your answer for x:

25 mg x / 25 mg = 450 mg ml / 25 mg

x = 18 ml (450/25)

so you will give 18 ml to the patient. you did not need to convert it to mcg because they are both in mg already. if one of them is in mcg, then you will have to convert.

i hope this will help with your future dosage calculations. this is just basic math so don't be intimidated.

good luck!

angel, rn