Journal of child neurology
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Fosphenytoin, a prodrug of phenytoin, is rapidly and completely converted to phenytoin in adults after intravenous or intramuscular administration and is significantly better tolerated than parenteral phenytoin. Fosphenytoin is highly plasma-protein bound and, when present in sufficient concentration, will displace phenytoin from plasma proteins. The clinical utility is that fosphenytoin may be used to achieve therapeutic phenytoin concentrations more rapidly than intravenous phenytoin infused at its maximum recommended rate. ⋯ Adverse events associated with fosphenytoin generally were related to the central nervous system and were similar to those associated with phenytoin, except for a higher incidence of transient pruritus with fosphenytoin. Intravenous fosphenytoin has significant advantages over intravenous phenytoin: It requires a shorter infusion time and fewer intravenous disruptions, causes less pain and burning at the infusion site and minimal consequences in case of intravenous infiltration, allows longer maintenance of intravenous sites, and has better intravenous fluid compatibility and stability. In contrast to intramuscular phenytoin, intramuscular fosphenytoin is well tolerated in both large loading doses and maintenance doses.
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The pharmacologic interventions for treatment of acute repetitive seizures and those for treatment of status epilepticus are similar. The choice of treatment should be based on the drug's onset of action, spectrum of anticonvulsant activity, route and ease of administration, elimination half-life, therapeutic margin of safety, and redistribution from the central nervous system. ⋯ Short-acting benzodiazepines, including diazepam, lorazepam, clonazepam, and midazolam, can decrease the frequency of emergency department visits if given at the appropriate times. The recently approved intravenous formulation of valproate may be of use in children receiving oral valproate who develop breakthrough seizures caused by subtherapeutic plasma levels that are secondary to missed doses or an inability to tolerate oral valproate.