"Maintenance dose" math question.

[Nursing2102]

I am stumped on this question because my co-worker got a different answer than I did and she is convinced her answer is right.

Question: A patient admitted today with seizure disorder is to receive Dilantin 20mg/kg/day in three equally divided doses over the next 24 hours. This is to be followed by a maintenance dose of 5mg/kg/day in three equally divided doses every 8 hours. The patient weighs 165lbs.

A.) How many mg of the Dilantin should the patient receive per dose on day one? -----My answer: 500mg, my co-workers answer: 625mg.

B.) Based on the information given in the question, how many mg of maintenance dose of Dilantin should the patient receive per dose?

------My answer & co-workers answer: 125mg (we agree on this one!)

For A, I did 20mg x 75kg which is 1500mg, divided by 3 doses = 500mg.

My co-worker did the same thing as me only she added one of the maintenance doses (126mg) to the 500....... because she thinks the maintenance dose is given with the original dose from day 1.

Anyone agree with my answer?

[meanmaryjean, DNP, RN]

You friends failed to read 'this is to be followed by....'. Maintenance dose happens AFTER the loading dose, not with.

[NicuGal, MSN, RN]

Always read it all the way. Usually loading doses are not combined with a maintenance dose.

[AngelFireMama]

They are correct!!! Dilantin would first be given as a loading dose, and then be "maintained". You would not combine a loading dose with a maintenance dose!!

[nurseprnRN, BSN, RN]

I am stumped on this question because my co-worker got a different answer than I did and she is convinced her answer is right.

Question: A patient admitted today with seizure disorder is to receive Dilantin 20mg/kg/day in three equally divided doses over the next 24 hours. This is to be followed by a maintenance dose of 5mg/kg/day in three equally divided doses every 8 hours. The patient weighs 165lbs.

A.) How many mg of the Dilantin should the patient receive per dose on day one? -----My answer: 500mg, my co-workers answer: 625mg.

B.) Based on the information given in the question, how many mg of maintenance dose of Dilantin should the patient receive per dose?

------My answer & co-workers answer: 125mg (we agree on this one!)

For A, I did 20mg x 75kg which is 1500mg, divided by 3 doses = 500mg.

My co-worker did the same thing as me only she added one of the maintenance doses (126mg) to the 500....... because she thinks the maintenance dose is given with the original dose from day 1.

Anyone agree with my answer?

You are correct.

The loading dose over the first three doses is calculated to get the patient's blood level up. After that, the maintenance dose is calculated to keep it there while the body metabolism is breaking it down.

Your coworker is is both unclear on the concept of loading dose vs. maintenance and of making a serious medication error if she gives the maintenance dose and the loading dose from the beginning, running the risk of overdosing the patient by changing the prescribed dose without authorization. Because she doesn't know what loading dose (and related concepts critical to this process, like "half life") means.