Anticonvulsant levels and reloading

Background

DOSE

Dose (mg) = weight^ (kg) X volume of distribution X [desired level - current level (mcg/mL)]

^Ideal body weight

VOLUME OF DISTRIBUTIONS

Phenytoin (dilantin) 0.8

Carbamazepine (tegretol) 0.8

Phenobarbital 0.6

Valproate (depakote) 0.2

DESIRED LEVEL

1. If patient's optimal levels known = desired level
2. If not, target upper end of therapeutic range:
   1. Phenytoin = 20 mcg/mL
   2. Phenobarbital = 40 mcg/mL
   3. Valproate = 100 mcg/mL

Treatment

1. Iv load can be performed with phenobarbital, phenytoin/fosphenytoin, valproate, or levetiracetam.
2. Oral loading often limited by neurotoxic adverse effects (n/v) , but can spread dose out over a day or more if necessary.
   1. (e.g. phenytoin PO 400 mg Q4 to reach the final dosage)

See Also

Neuro: Seizure Levels and Reloading

Peds: Seizure (Peds)

Peds: Febrile Seizure

Source

DONALDSON 3/08 (from emedicine; Treiman 1997; Bourgeois, 1996)