Anticonvulsant levels and reloading

Background

• IV load can be performed with phenobarbital, phenytoin, valproate, levetiracetam
• Oral loading can be spread over day or more to avoid GI upset

Dose

Dose (mg) = ideal body weight (kg) X Vd X [desired level - current level (mcg/mL)]

Volume of Distribution

Agent	Volume of Distribution
Phenytoin (dilantin)	0.8
Carbamazepine (tegretol)	0.8
Phenobarbital	0.6
Valproate (depakote)	0.2

Desired Level

• Pt's optimal level = desired level
  • If optimal level unknown target upper end of therapeutic range:
    • Phenytoin = 20 mcg/mL
    • Valproate = 100 mcg/mL
    • Phenobarbital = 40 mcg/mL

Loading

• Phenytoin
  • IV: 10-20mg/kg at max rate of 25mg/min
  • PO: 18mg/kg as single dose or divided into 3 doses q2hr
• Fosphenytoin
  • IV: 10-20mg phenytoin equivalent at max rate of 150mg/min

See Also

• Seizure (Peds)
• Febrile Seizure
• Dilantin Load
• Depakote Loading

Source

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