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My question is regards to phenytoin monitoring and dose adjustment in a seizing patient in the ICU. They will usually get a 1gm IV load. But from the period between this loading dose and BEFORE they reach steady state (~7 days in most patients), how do you interpret and adjust serum levels? Please don't lecture me on the michaelis menten kinetics lol.
First question is after the loading dose...
After an IV load you take a level within the first few hours. However, are they any good rules of thumb or guides to show what you do with this level? If it's too high (>20) then you can hold the maintenance dose...but for how long? If its too low then you reload? How much?
Second question is between the loading dose and before steady state...
After you start a maintenance dose (usually 100mg IV TID), then how often do you draw levels and make dose adjustments? I've seen a couple cases where I work where they draw levels every day. This seems excessive correct?
This is from lexicomp that answers the second question but does anyone know of a good literature derived kinetic parameters?
"Rapid achievement: Draw within 2-3 days of therapy initiation to ensure that the patient's metabolism is not remarkably different from that which would be predicted by average literature-derived pharmacokinetic parameters; early levels should be used cautiously in design of new dosing regimens "
Thanks
First question is after the loading dose...
After an IV load you take a level within the first few hours. However, are they any good rules of thumb or guides to show what you do with this level? If it's too high (>20) then you can hold the maintenance dose...but for how long? If its too low then you reload? How much?
Second question is between the loading dose and before steady state...
After you start a maintenance dose (usually 100mg IV TID), then how often do you draw levels and make dose adjustments? I've seen a couple cases where I work where they draw levels every day. This seems excessive correct?
This is from lexicomp that answers the second question but does anyone know of a good literature derived kinetic parameters?
"Rapid achievement: Draw within 2-3 days of therapy initiation to ensure that the patient's metabolism is not remarkably different from that which would be predicted by average literature-derived pharmacokinetic parameters; early levels should be used cautiously in design of new dosing regimens "
Thanks
