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
- May use IV vs PO reload at physican discretion[1]
Initial Loading[1]
| Anticonvulsant (brand name) | Loading Dose and Route of Administration |
| Carbamazepine (Tegretol) | PO: 8 mg/kg suspension in single oral load
IV: not available |
| Gabapentin (Neurontin) | PO: 900 mg/day oral (300 mg tid) for 3 days
IV: not available |
| Lacosamide (Vimpat) | PO: dosages not studied
IV: not studied |
| Lamotrigine (Lamictal) | PO: 6.5 mg/kg single oral load if on lamotrigine for >6 mo without a history of rash or intolerance in the past and only off lamotrigine for <5 days
IV: not available |
| Levetiracetam (Keppra) | PO: 1,500 mg oral load
IV: rapid IV loading safe and well tolerated in doses up to 60 mg/kg |
| Phenytoin (Dilantin) | PO: 20 mg/kg divided in maximum doses of 400 mg every 2 hours
IV: 18 mg/kg at maximum rate of 50 mg/min |
| Fosphenytoin (Cerebyx) | PO:
IV: 18 PE/kg IV at maximum rate of 150 PE/min IM: administration possible |
| Valproate (Depacon) | PO:
IV: Up to 30 mg/kg IV at max rate of 10 mg/kg/min |
Levels
Medications with verifiable levels include:
Desired Levels
- 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
- Carbamazepine = 12 mcg/mL
- If optimal level unknown target upper end of therapeutic range:
Reloading
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 |