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
- If optimal level unknown target upper end of therapeutic range:
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)