Question

You receive an order for ampicillin 200 mg/kg/day divided every 6 hours to treat community acquired pneumonia for a pediatric patient who weighs 42 pounds. The vials of ampicillin that you have in stock contain 1 gram of ampicillin/vial and require reconstitution with 3.5 mL of diluent (sterile water for injection). How many milliliters (mL) should be withdrawn from the reconstituted vial to prepare one dose of ampicillin for this child? Please round the final answer to onedecimal place, except no trailing zeros.

Weight of the child is 42pound ie19 kg So total dose of medication needed is =19× 200 =3800mg ÷ 4= 950mg every 6th hourly . Required dose=(desired dose ÷available dose) ×dilution = ( 950÷1000)3.5 =3.3ml =3ml 3ml of ampicillin is needed for a single dose

QUESTION:

What is the powder volume in milliliters (mL) in the ampicillin vial above? Please round the final answer to onedecimal place, except no trailing zeros.

Answer 1

Powder volume means the volume that the powder occupies after getting dissolved in a solution or fluid.

Powder volume can be measured by subtracting the Final volume from the required volume of diluent

Where Final volume is the total amount of medication after reconstitution with prescribed amount of diluent

Diluent is the liquid added to a powdered drug for reconstitution

Steps:

Weight of the child = 42 pounds = 19kg

Dose in hand = 1 gram (1000mg) of ampicillin/vial

After reconstitution 3.5 mL of diluent = 1gm of ampicillin

Doctor's order : Ampicillin 200 mg/kg/day

= 200 x 19 = 3800mg per day

Divide into 4 equal doses to administer 6th hourly = 3800 / 4 = 950mg 6th hourly

1000mg = 3.5ml

950mg = ____ml

___ml = (950 x 3.5) / 1000

= 3.3ml

So 3.3 ml contains 950mg of Ampicillin to be administered in one dose.

3.3 ml of diluent = 950mg

in 1ml solution ____mg of ampicillin is present

mg of ampicillin present in 1ml = 950/3.3 = 287.8

= 288 mg

Here 3.5 ml of sterile water is to be added to 1gm vial of ampicillin

3.5ml = 1000gm

So the powder volume can be calculated by subtracting the final volume in ml by the required amount of diluent for one dose

Here Final volume = 3.5ml

Amount of diluent required = 3.3ml

So 3.5 - 3.3 = 0.2ml

So the powder volume = 0.2ml

If you consider 3ml instead of 3.3ml of diluent after rounding off

Then substract 3.5 from 3

3.5 - 3 = 0.5ml

In that case powder volume will be 0.5ml.

But the solution given at first with powder volume of 0.2ml is the most appropriate answer.