Im having trouble understanding these math questions for medication reconstitution

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Erythromycin Ethylsuccinate oral suspension bottle instructs you to add 53 mL of water and shake vigorously. This makes 100 mL suspension for a concentration of 200mg per 5mL. Refrigerate after mixing.

pt care orders read: give 550mg of Erythromycin Ethylsussiante by mouth every 8 hours. How much will you administer?

Ceftriaxone 1 g reconstituting options, option 1: add 3.6 mL of sterile water to obtain 250mg/mL concentration

Ordered Ceftriaxone 750 mg IV q 6 h How much will you draw up?

Ordered Ceftriaxone 450 mg IV q 4 h How much will you draw up?

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Specializes in Medical and general practice now LTC.

What are your thoughts? Just pick one and explain your thoughts

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Just now, Silverdragon102 said:

What are your thoughts? Just pick one and explain your thoughts

Okay, I may be wrong but the equation is d/h*q and for the first one, I went 550/200*5 to get 13.75 which, I rounded to 13.8mL and for the second ones, I went with 750/250*1=3mL and 450/350*1=1.285 rounded to 1.3mL

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Specializes in Medical and general practice now LTC.

For the last one I get 1.8 ml. Don’t forget that the direction you gave was 250mg/ml and you did 350. Other 2 doses are same as what I got

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9 hours ago, Silverdragon102 said:

For the last one I get 1.8 ml. Don’t forget that the direction you gave was 250mg/ml and you did 350. Other 2 doses are same as what I got

Thanks

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Specializes in Cardiac, Perioperative care, research.

1. 200÷5=40, 550÷40=13.75 rounded off to 13.8
2. 1ml=250, 3x250=750

3. 1m=250, 450÷250=1.8

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