Anticonvulsant levels and reloading

Revision as of 08:38, 28 January 2012 by Jswartz (talk | contribs)

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

  • First-time load or level ~0
    • IV: 10-20mg/kg at max rate of 25mg/min
    • PO: 18mg/kg as single dose or divided into 3 doses q2hr
  • Level above 0 (to avoid over-dosing)
    • (100-level) X 0.25 X wt
    • Give over 1hr

Fosphenytoin

  • IV: 15-20mg PE/kg at 100-150mg/min

See Also

Source

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