Anticonvulsant levels and reloading


  • 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]

Drug (with brand name) Loading Dose and Route of Administration
Carbamazepine (Tegretol) 8 mg/kg oral suspension;

single oral load; IV not available

Gabapentin (Neurontin) 900 mg/day oral (300 mg tid) for 3 days;

IV not available

Lacosamide (Vimpat) Oral and IV formulations available and safe;

loading dosages not studied

Lamotrigine (Lamictal) 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) 1,500 mg oral load;

rapid IV loading safe and well tolerated in doses up to 60 mg/kg

Phenytoin (Dilantin) 20 mg/kg divided in maximum doses of 400 mg every 2 h orally;

or 18 mg/kg IV at maximum rate of 50 mg/min

Fosphenytoin (Cerebyx) 18 PE/kg IV at maximum rate of 150 PE/min;

IM administration possible

Valproate (Depacon) Up to 30 mg/kg IV at max rate of 10 mg/kg/min IV


Medications with verifiable levels include:

  1. Phenytoin
  2. Carbamazepine
  3. Phenobarbital
  4. Valproate

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



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

Volume of Distribution

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

See Also


  1. 1.0 1.1 Seizures ACEP Policy committee . Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients Presenting to the Emergency Department With Seizures. Ann Emerg Med. 2014;63(4):437–447.e15. doi:10.1016/j.annemergmed.2014.01.018.