mental status Another dose may be repeated after minutes An alternative is diazepam (Valium), 0.15 to 0.2 mg/kg IV (usual maximum 10 mg/dose), which has a similarly rapid onset of action If IV or intraosseous access cannot be established, diazepam may be administered rectally in a dose of 0.5 mg/kg (maximum 20 mg/dose), instilling the IV formulation with a slip-tip syringe (remove needle) or by using a specific rectal gel preparation All the benzodiazepines can cause sedation and respiratory depression, which may persist for hours Equipment for establishing an airway and supporting respiration must be available, especially if repeated doses are used Ideally, noninvasive ETCO2 monitoring will be used to help assess ventilation in addition to auscultation and pulse oximetry Hypotension is uncommon but may be a problem with multiple doses or when barbiturates are administered concomitantly If the seizures have not been controlled within 10 minutes with benzodiazepines, a second-line agent should be administered Current evidence does not strongly support a preferred second-line agent Appropriate options to consider include fosphenytoin, valproic acid (VPA), and levetiracetam Consideration should be given to current AED therapy when making a choice Fosphenytoin is a prodrug of phenytoin, which is rapidly metabolized to the active form It offers several advantages over phenytoin, including more rapid administration and fewer local and systemic side effects Fosphenytoin may also be given IM, unlike phenytoin The dose of the two drugs is identical; fosphenytoin doses are expressed as phenytoin equivalents (PE) The loading dose of fosphenytoin is 20 mg PE/kg IV, maximum single dose of 1,500 mg PE/dose, at a rate of mg PE/kg/min to a maximum of 150 mg/min In the absence of any clinical effect, an additional 10 mg/kg IV may be administered Cardiac monitoring is required because rapid IV infusion may lead to hypotension, QT prolongation, and cardiac dysrhythmias If phenytoin is used instead, the maximum rate of administration is mg/kg/min in children and 50 mg/min in an adult In patients known to be taking phenytoin chronically, a smaller dose of to 10 mg/kg should be used initially unless the serum level is known to be very low Each mg/kg of phenytoin administered raises the serum level by approximately μg/mL, although phenytoin kinetics are unpredictable Phenytoin is highly lipid soluble and reaches therapeutic levels in the brain within 10 to 20 minutes, with duration of action of 12 to 24 hours Unlike other anticonvulsant medications, phenytoin does not cause sedation or respiratory depression