do not stop after the second dose of phenobarbital, phosphenytoin is used.
Phosphenytoin is a prodrug of phenytoin. Plasma phosphatase enzymes cleave
phenytoin from phosphenytoin. Phosphenytoin acts on sodium current. The
loading dose is 10 mg/kg. It should be infused intravenously at a rate
no faster than 1 mg/kg per minute (same as phenobarbital). If the seizure
persists after 10 minutes, a second dose of phosphenytoin of 10 mg/kg
should be administered. If the seizure stops, no further antiepileptic
medication is given and a phenytoin level is taken after 6 hours. The
maintenance dose of intravenous phosphenytoin is 3 to 5 mg/kg per day
divided in two doses. Phosphenytoin is as cardiotoxic as phenytoin. The
advantage of phosphenytoin is that it is water soluble and has less toxicity
at the site of infusion.
phenobarbital and phosphenytoin do not stop the seizures, the patient
should be placed on continuous EEG recording or near infrared spectroscopy
and 0.1 mg/kg intravenous lorazepan should be administered.
The same dose of lorazepan may be repeated in 10 minutes if the seizure
persists. Another option in patients unresponsive to phenobarbital and
phosphenytoin is to use intravenous valproic acid. Intravenous valproic
acid may be useful to achieve a therapeutic level quickly. The intravenous
dose of valproic acid can be calculated by considering that each 1 mg/kg
of valproic acid given intravenously raises the serum concentration by
about 3 micrograms per milliliter.Elevation
of serum ammonia may occur with intravenous valproic acid.
Oral antiepileptic drugs are
used as soon as possible if seizures stop or are relatively controlled.
Phenobarbital, phenytoin, valproic acid, carbamezapine, and lamotragine
can be used. The dose of carbamezapine is 5 mg/kg every 12 hours. No loading
dose is necessary. Carbamezapine acts on sodium current. The loading dose
of oral valproic acid is 20 to 26 mg/kg. The maintenance dose of oral
valproic acid is 5 to 10 mg/kg.
Valproic acid acts on sodium current and GABA receptors. Carbamezapine
and valproic acid levels should be monitored and kept within the usual
therapeutic range. Lamotrigine at a dose of 4.4 mg/kg per day can be used
as a single dose for 3 days and then divided in two doses.
Brain surgery should be considered in cases of focal pathology.