Need help!!!!! Dosage calculations

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The doctor orders Phenobarbital 10 mg q12h for a child weighing 9 lb. The Pediatric Drug handbook states maintenance dose is 3 to 5 mg/kg/day q12h. Phenobarbital Elixir is available in dosage strength of 20 mg per 5 ml. If safe, what will you administer for one dose?

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I've tried absolutely everything... I'm just not getting it and I'm very frustrated!!!!!

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I've tried absolutely everything... I'm just not getting it and I'm very frustrated!!!!!

Why don't you show us what you've done so far? This will allow us to see where you are having problems, and better assist you in working through this problem.

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I honestly don't even know how to start it. I don't know if I start off with the dosage on hand or the dose the doctor gives!!!... I've never had a problem that says mg/kg/day so I'm totally confused!!!!..

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These are the questions that you need to answer. When you have these you can calculate the volume of medication required.

  • What is the total daily dose of phenobarbital to be administered to the patient?
  • How many kg are in 9 lbs?
  • Based on the weight in kg and the dosing range provided, what are the minimum and maximum daily doses for this patient?

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Okay so.. The total daily dose would be 10mg every 12 hours?... 9lb÷2.2lb= 4.09kg...that's as far as I get..when I look at that 3 to 5 mg/kg/day q12h I'm still confused

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Okay so.. The total daily dose would be 10mg every 12 hours?... 9lb÷2.2lb= 4.09kg...that's as far as I get..when I look at that 3 to 5 mg/kg/day q12h I'm still confused

The 3 - 5 mg/kg/day is the total safe dose of medication to be administered in one day. Based on this, what would the total daily dose be, for a patient with a weight of 4.09 kg?

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Would I set it up like this then?

dose = 4.09kg/10mg X 20mg/5mL X 12hr?

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No, not at all. I will work a similar problem to demonstrate how I would complete this.

The physician orders digoxin, 175 mcg q8 hours. The patient weighs 22 lbs. The total digitalizing dose is 35 – 60 mcg/kg, to be administered in three equal doses. Digoxin is available as an oral solution containing 50 mcg/mL. If this is a safe dose, how many mL will you administer for one dose?

175 mcg * 3 doses = 525 mcg

22 lb * (1 kg/2.2 lb) = 10 kg

10 kg * (35 mcg/kg) = 350 mcg; 10 kg * (60 mcg/kg) = 600 mcg. 175 mcg is a safe dose

175 mcg * (1 mL/50 mcg) = 3.5 mL total volume to administer

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Specializes in OR, Nursing Professional Development.
Would I set it up like this then?

dose = 4.09kg/10mg X 20mg/5mL X 12hr?

Well, no. You're trying to cram way too much into that equation.

You need to break it down into steps and what information goes into those steps.

Step 1: Minimum therapeutic dose (this is where that 3-5mg/kg/day comes in)

Step 2: Maximum safe dose (as with step 1, this is where those numbers come in)

Do you understand what the mg/kg/day means? Why not tell us what you think and we'll let you know if you're on the right track.

Step 3: What dose is prescribed and how much of the medication would be administered in 24 hours?

Step 4: Does the number from step 3 fall into the safe range?

Step 5: Using the prescribed dose and what you have on hand, how much do you administer?

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It means 3-5mg per kg per day... right?

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Specializes in Med-Tele; ED; ICU.
It means 3-5mg per kg per day... right?
yes, 5 mg/kg is the maximum safe total daily dose. Since you're going to be giving it every 12 hours, what's the max for each dose?

Half of it, right?

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