Efficacy and safety of fosphenytoin for acute encephalopathy in children

Fosphenytoin vs. continuous midazolam for pediatric febrile status epilepticus

BACKGROUND

Fosphenytoin (fPHT) and continuous intravenous midazolam (cMDL) had commonly been used as second-line treatments for pediatric status epilepticus (SE) in Japan. However, there is no comparative study of these two treatments.

METHODS

We included consecutive children who 1) were admitted to Kobe Children's Hospital because of convulsion with fever and 2) were treated with either fPHT or cMDL as second-line treatment for convulsive SE lasting for longer than 30 min. We compared, between the fPHT and cMDL groups, the proportion of barbiturate coma therapy (BCT), incomplete recovery of consciousness, mechanical ventilation, and inotropic agents.

RESULTS

The proportion of BCT was not significantly different between the two groups (48.7% [20/41] in fPHT and 35.3% [29/82] in cMDL, p = 0.17). The prevalence of incomplete recovery of consciousness, mechanical ventilation, and inotropic agents was not different between the two groups. After excluding 49 patients treated with BCT, incomplete recovery of consciousness 6 h and 12 h after onset was more frequent in the cMDL group than in the fPHT group (71.7% vs. 33.3%, p < 0.01; 56.6% vs. 14.2%, p < 0.01; respectively). Mechanical ventilation was more frequent in the cMDL group than in the fPHT group (32.0% vs. 4.7%, p = 0.01).

CONCLUSIONS

Our results suggest that 1) the efficacy of fPHT and cMDL is similar, although cMDL may prevent the need for BCT compared with fPHT, and 2) fPHT is relatively safe as a second-line treatment for pediatric SE in patients who do not require BCT.

Fosphenytoin Population Pharmacokinetics in the Acutely Ill Pediatric Population

OBJECTIVE

The purpose of this study is to describe the pharmacokinetics of phenytoin in pediatric patients receiving fosphenytoin.

DESIGN

Retrospective, population pharmacokinetic analysis.

SETTING

Emergency department or PICU of a large tertiary care children's hospital.

PATIENTS

Patients less than 19 years old who received fosphenytoin in the PICU or emergency center for treatment of seizures from January 2011 to June 2017 were included.

INTERVENTIONS

Population pharmacokinetic analysis was performed with NONMEM v7.3 (Icon Plc, Dublin, Ireland). Simulation was performed to determine optimal loading dose and maintenance dosing regimens.

MEASUREMENTS AND MAIN RESULTS

A total of 536 patients (55.4% male; median age, 3.4 yr [interquartile range, 0.92-8.5 yr]) met study criteria. Fosphenytoin was administered at median 15.1 mg/kg/dose (interquartile range, 6.3-20.7 mg/kg/dose). Mean serum concentrations of 17.5 ± 7.8 mg/L were at a median 4.2 hours (interquartile range, 2.5-7.8 hr) after a dose. A pharmacokinetic model with two compartments, allometrically scaled fat-free mass on all parameters, and serum creatinine and concomitant phenobarbital use on clearance had the best fit. Simulation demonstrated that a 20 mg/kg loading dose followed by 6 mg/kg/dose every 8 hours had the greatest percentage of concentrations in the 10-20 mg/L range, with reduced doses to achieve therapeutic in patients with reduced kidney function.

CONCLUSIONS

A loading dose of 20 mg/kg followed by 6 mg/kg/dose every 8 hours based on fat-free mass is a reasonable empiric strategy for attainment and maintenance of therapeutic trough concentrations. Concomitant phenobarbital use may increase clearance of phenytoin and fosphenytoin dose reductions should occur in patients with reduced kidney function.

Acute Leukoencephalopathy with Restricted Diffusion

Treatment and outcome of children with acute encephalopathy depend on the cause, prompt treatment of the underlying cause, and use of adequate supportive measures. Many novel causes of acute encephalopathy are emerging where lumbar puncture, computed tomography of the head, and routine biochemical testing can be normal such as acute disseminated encephalomyelitis and febrile infection-related refractory epilepsy syndrome. Magnetic resonance imaging (MRI) plays an important role in the workup of children with acute leukoencephalopathy. Despite this in few cases, a correct diagnosis is not possible and novel conditions have been described in the last decade. One such condition is acute encephalopathy with biphasic seizures and restricted diffusion also called as acute leukoencephalopathy with restricted diffusion. Here, the routine MRI sequences such as T1, T2, and fluid-attenuated inversion recovery sequences can be normal. Here, we have reviewed the etiology, types, clinicoradiological features, and treatment of this condition.

Efficacy and safety of fosphenytoin for benign convulsions with mild gastroenteritis

OBJECTIVE

To clarify the efficacy and safety of fosphenytoin for seizures in children with benign convulsions and mild gastroenteritis.

METHODS

Using the mailing list of the Annual Zao Conference on Pediatric Neurology, we recruited patients who met the following criteria: (1) clinical diagnosis of benign convulsions with mild gastroenteritis and (2) treatment with intravenous fosphenytoin. Benign convulsions with mild gastroenteritis were defined as a condition of (a) seizures associated with gastroenteritis without electrolyte imbalance, hypoglycemia, or dehydration in patients (b) between 6 months and 3 years of age with (c) no preexisting neurological disorders, (d) no impaired consciousness, and (e) a body temperature less than 38.0 °C before and after the seizures. The efficacy of fosphenytoin was categorized as effective when cessation of seizures was achieved.

RESULTS

Data from 16 child patients were obtained (median age, 20 months). Seizures were completely controlled after the initial dose of fosphenytoin in 14 of 16 patients. The median loading dose of fosphenytoin was 22.5 mg/kg. In 10 patients, fosphenytoin was administered after other antiepileptic drugs such as diazepam and midazolam were used. Adverse effects of fosphenytoin, excessive sedation, or intravenous fluid incompatibility were not observed in any patients.

CONCLUSION

Fosphenytoin is effective and well tolerated among children with benign convulsions with mild gastroenteritis.