# Am I doing this right?

Student Assist   (3,321 Views | 8 Replies)

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Im taking a dosage calc class and I just wanted to make sure I'm doing the problems right.

The recommended safe dose for a child of erythromycin is 20 mg/kg/day in four equal doses (weight: 33 lbs) The medication is supplied in 125 mg/mL.

A. calculate weight for child.

B. calculate safe dose for this child. Mg/dose

C. How many mL will be administered for each dose?

i got:

a: 15kg

b. 75mg/dose

c. 0.6 mL

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pmabraham has 3 years experience as a BSN, RN and specializes in Hospice, Palliative Care.

2 Articles; 2,529 Posts; 46,072 Profile Views

Good day, amiee1999:

As I share this, keep in mind, I'm learning dosage calculations myself. I also came up with 0.6 mL per dose.

33 lbs / 2.2 = 15 kg

15 kg x 20 mg/ kg/day = 300 mg/ day / 125 mg/mL = 2.4 mL. 2.4 mL / 4 = 0.6 mL per dose.

Thank you.

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43 Posts; 2,559 Profile Views

I'm learning dimensional analysis. How are you doing your dosage calculation?

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pmabraham has 3 years experience as a BSN, RN and specializes in Hospice, Palliative Care.

2 Articles; 2,529 Posts; 46,072 Profile Views

Good day, amiee1999:

I was accepted into clinicals this past Saturday; and we need to pass a dosage calculation test with a 100% pass or fail prior to the semester starting. Right now, I'm just using Calculate with Confidence 5th edition plus dosagehelp.com; another person posted about testandcalc.com as well. Is that what you were asking?

Btw, I just noticed it now.. the "b" answer doesn't make sense. If the medication is in mg / ml, how are you coming up with 75 mg? Since this is a liquid, how would you give a mass-based dose?

Thank you.

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43 Posts; 2,559 Profile Views

I was wondering what formula are you using to figure out your calculations. I'm being taught dimensional analysis but I hear there are many ways to do med math, so I'd like to see what else is out there because I'm not too sure on DA.

To answer your second question; erythromycin is 20 mg/kg/day, and since the converted lbs to kg, I multiplied my weight in kg to 20, which gave 300 mg a day, and divided that by 4 to get individual dose, since B is asking mg/dose

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pmabraham has 3 years experience as a BSN, RN and specializes in Hospice, Palliative Care.

2 Articles; 2,529 Posts; 46,072 Profile Views

Good day amiee1999

Thank you.

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43 Posts; 2,559 Profile Views

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The recommended safe dose for a child of erythromycin is 20 mg/kg/day in four equal doses (weight: 33 lbs) The medication is supplied in 125 mg/mL.

A. calculate weight for child.

B. calculate safe dose for this child. Mg/dose

C. How many mL will be administered for each dose?

i got:

a: 15kg

b. 75mg/dose

c. 0.6 mL

A. 33 lbs divided by 2.2 = 15kg

B. 20mg/kg/day = 20 x 15 = 300mg / day; four divided doses would be 75mg each

C. drug is 125mg/cc; 75 mg / 125 mg = 0.6 cc

Perfect!

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87 Posts; 1,419 Profile Views

You can also cross multiply using basic algebra after you determine the weight and divide the amount into 4 doses.

125mg 75mg

______ X _____

1mL X mL

You are trying to determine mL's to administer.

Multiply diagonally:

125mg x XmL

75mg x 1mL

125X = 75

X = 75

____

125

X = 0.6 mL