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Are my dosage reconstitution problems correct?

Mursely Mursely (New) New

Order: Ampicillin 750mg im q6h

Supply: 1 gram vial of ampicillin

Directions: add 2.4 ml sterile water to yield 2.5 ml of soltuion

750 mg x 2.5 ml = 1875

1 gram = 1000 mg

D/H = 1875/1000 = 1.9 ml.

Order: Nafcillin 750 mg IM qid

Supply: Nafcillin 2 gram vial

Directions: add 6.8 ml sterile water for total of 8 ml of solution.

750 mg x 8 ml = 6000

2 gram = 2000 mg

D/H= 6000/2000 = 3 ml.

Order: Ampicillin 750mg im q6h

Supply: 1 gram vial of ampicillin

Directions: add 2.4 ml sterile water to yield 2.5 ml of soltuion

750 mg x 2.5 ml = 1875 ... Note: You cannot arbitrarily drop units... they have meaning and are treated algebraically just as are numbers and variables... This should say: 1875 mg ml

1 gram = 1000 mg

D/H = 1875/1000 = 1.9 ml. Same deal... you pulled "ml" out of thin air... rather, it should be: "1875 mg ml / 1000 mg = 1.9 ml"

Order: Nafcillin 750 mg IM qid

Supply: Nafcillin 2 gram vial

Directions: add 6.8 ml sterile water for total of 8 ml of solution.

750 mg x 8 ml = 6000

2 gram = 2000 mg

D/H= 6000/2000 = 3 ml.

Same deal... disappearing and reappearing units... gonna bite you in the butt...

Your numbers appear correct (though I didn't check the math) but your intermittent use of units is (a) improper, and (b) a recipe for disaster.

pmabraham, BSN, RN

Specializes in Hospice, Palliative Care. Has 3 years experience.

Good day, Mursely:

I appreciate you and others who are posting dosage calculation problems as it gives all of us practice; thank you. Your math looks good, though a lot of times I see the formula method as D/H * Q. I don't know if any of your instructors would be like the nuns I had in middle school with rulers smacking knuckles, but I can envision that if you get picky proctors for a test.

Thank you.

Edited by pmabraham

The numbers are correct. Thanks for the practice.

Order: Ampicillin 750mg im q6h

Supply: 1 gram vial of ampicillin

Directions: add 2.4 ml sterile water to yield 2.5 ml of soltuion

750 mg x 2.5 ml = 1875

1 gram = 1000 mg

D/H = 1875/1000 = 1.9 ml.

Order: Nafcillin 750 mg IM qid

Supply: Nafcillin 2 gram vial

Directions: add 6.8 ml sterile water for total of 8 ml of solution.

750 mg x 8 ml = 6000

2 gram = 2000 mg

D/H= 6000/2000 = 3 ml.

I agree totally with music in my heart's post to you. You need to take care to keep track of units and such:

2.5mL/1000mg * 750mg = 1.875mL =1.9mL

8mL/2000mg * 750mg = 3mL

Kuriin, BSN, RN

Specializes in Emergency. Has 4 years experience.

Good day, Mursely:

I appreciate you and others who are posting dosage calculation problems as it gives all of us practice; thank you. Your math looks good, though a lot of times I see the formula method as D/H * Q. I don't know if any of your instructors would be like the nuns I had in middle school with rulers smacking knuckles, but I can envision that if you get picky proctors for a test.

Thank you.

I'm confused, what is wrong with the above's formula? I've personally always read it as Want/Have*Vehicle.

Just trying to figure out what would the pickiness be about. :o

pmabraham, BSN, RN

Specializes in Hospice, Palliative Care. Has 3 years experience.

Good day, Kuriin:

Re-read Mursely's post to see if the formula was used in form or not, then re-read my post.

Thank you.

Kuriin, BSN, RN

Specializes in Emergency. Has 4 years experience.

Whoooops. Didn't realize he/she didn't use the W/H*V formula. Whatever works. :)

loveofrn, BSN, RN

Specializes in MICU. Has 3 years experience.

I still dont know how to use the above formula. The method that works for me is to know what the problem is asking and then solve it in dimensional analysis or in ratio. I think before jumping to any formula, we need to understand the question, then dosage math would be easier than abc

THELIVINGWORST, ASN, RN

Specializes in Public Health. Has 4 years experience.

Dimensional analysis always works so you don't get confused.

loveofrn, BSN, RN

Specializes in MICU. Has 3 years experience.

Dimensional analysis always works so you don't get confused.

Not everytime!!! I learned that the hard way

Your method confused me, but I came up with the same answers, so it looks good to me.

loveofrn, BSN, RN

Specializes in MICU. Has 3 years experience.

Your method confused me, but I came up with the same answers, so it looks good to me.

Whose method?

Whose method?

The op's

loveofrn, BSN, RN

Specializes in MICU. Has 3 years experience.

The op's

There are many methods. What matters most is understanding the question, then you can apply the method that works for you. I use DA most of the time.

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