Need help solving this problem about dosage?

Question

Hello. I've been wrestling with this problem all night and most of today. Couldsomeone walk me through the steps? Any help at all is extremely appreciated. I don't know what to do!!

Here is the question:

An I.V. is ordered for an infant. The infant is to receiv dillantin @ 15.0mg/kg body weight in a normal saline (0.9% NaCl) I.V. bag @ 0.5% (final solution of dilantin should be @ 0.5%). On the shelf in the medical cabinet you find: dilantin 6.0% (10ml vials), and Normal Saline(0.9% NaCl)(10ml vials and 1.0L bags). Weight of the infant=5.31 Ibs.

What are you going to do?

Answer 1

Hi Jasmine,

 

I am not a pharmacologist, doctor or nurse, but this is mostly a math and chemistry problem, and I can help you with that.

 

The infant weighs 5.31lb. 

 

Convert to kg = 5.31 lb / 2.2 lb/kg = 2.41 kg.

 

The patient needs 15 mg dilantin per kg of body weight = 15 mg/kg *2.41 kg = 36.2 mg of dilantin

 

The dilantin comes in 10ml vials of 6% solution. a 10ml vial = 10g (of water) *.06 (6%) = 600mg dilantin per vial

 

The final concentration is to be 0.5% so the dilantin solution needs to be mixed 11 parts saline with 1 part 6% dilantin.

 

The easiest way to do this is to draw 0.9 ml of the dilantin solution and inject it into a 10ml vial of Normal Saline and mix the solution well in the vial.  This will produce 10.9 ml of 0.5% dilantin solution.

 

This solution has 5mg of dilantin per ml (0.5%).  

 

We need 36.2 mg of dilantin so we measure 36.2 mg / 5 mg/ml = 7.25 ml.

 

Now you can inject the patient.

 

I hope this helps.

 

If you have any other questions ask away.  If this was helpful, please give the answer a thumbs up.

 

 

 

 

 

 

Answer 2

Great answer, I think it always helps to see the math being done