Dilantin Dosage

Generic name: phenytoin (oral)
Brand names: Dilantin, Phenytek
Drug classes: Group I antiarrhythmics, Hydantoin anticonvulsants

Medically reviewed by  A Ras MD.

Recommended Adult Dosing

Dosage forms:  ER CAP: 30 mg, 100 mg; CHEWABLE: 50 mg; SUSP: 125 mg per 5 mL

Dosage Forms Discontinued in US

[IM, IV not avail. as brand; see generic]

Status epilepticus

[initial tx]

Dose: 15-20 mg/kg/dose IV x1; Info: may give additional 10 mg/kg/dose IV x1 after 20min if no response to initial dose; begin maint. dose 12h after loading dose

[maintenance tx]

Dose: 100 mg PO/IV q6-8h; Info: adjust dose based on tx response and serum levels; taper dose gradually to D/C

Seizure disorder

[extended-release form]

Dose: 300-400 mg/day ER PO divided bid-tid; Max: 400 mg/dose ER; Alt: 4-7 mg/kg/day ER PO divided bid-tid; Info: may consider load of 15-20 mg/kg ER PO divided in 3 doses 2-4h apart; adjust dose based on tx response and serum levels; dose adjustment may be needed during pregnancy and/or postpartum; if divided doses unequal, give larger dose qhs; if stable on bid-tid ER dosing, then may switch to qd ER dosing; do not open ER cap; taper dose gradually to D/C

[immediate-release form]

Dose: 300-400 mg/day PO/IV divided bid-tid; Max: 400 mg/dose; Alt: 4-7 mg/kg/day PO/IV divided bid-tid; Info: may consider load of 15-20 mg/kg PO/IV divided in 3 doses 2-4h apart; adjust dose based on tx response and serum levels; dose adjustment may be needed during pregnancy and/or postpartum; if divided doses unequal, give larger dose qhs; taper dose gradually to D/C

Seizure prophylaxis, neurosurgery-assoc.

[*IV route]

Dose: 4-6 mg/kg/day IV divided bid-tid; Start: load 10-20 mg/kg IV divided in 3 doses 2-4h apart; Max: 400 mg/dose

[IM route]

Dose: 100-200 mg IM q4h; Max: x1wk; Alt: give 150% of usual daily PO dose by IM route divided q4h; Info: IV route preferred to IM route; decr. usual PO dose by 50% for same duration as IM was used when converting back from IM to PO

Renal dosing

renal impairment: no adjustment; Info: do not give oral loading regimen

HD/PD: no adjustment; no supplement; Info: do not give oral loading regimen

Hepatic dosing

[adjust dose amount]

hepatic impairment: do not give oral loading regimen

 Recommended Peds Dosing

Dosage forms:  ER CAP: 30 mg, 100 mg; CHEWABLE: 50 mg; SUSP: 125 mg per 5 mL

Dosage Forms Discontinued in US

[IV not avail. as brand; see generic]

Special Note

[formulation clarification]

Info: phenytoin ER caps contain 8% less drug than chewable tabs and susp; monitor closely and consider dose adjustment if switching between products

Status epilepticus

[15-20 mg/kg/dose IV x1]

Max: 1500 mg/day; Info: may give additional 10 mg/kg/dose IV x1 after 20min if no response to initial dose; begin maint. dose 12h after loading dose

Seizure disorder

[immediate-release form, <6 mo]

Dose: 5-8 mg/kg/day PO/IV divided bid-tid; Start: 5 mg/kg/day PO/IV divided bid; Info: adjust dose based on tx response and serum levels; if divided doses unequal, give larger dose qhs; taper dose gradually to D/C

[immediate-release form, 6 mo-3 yo]

Dose: 8-10 mg/kg/day PO/IV divided bid-tid; Start: 5 mg/kg/day PO/IV divided bid; Info: adjust dose based on tx response and serum levels; if divided doses unequal, give larger dose qhs; taper dose gradually to D/C

[immediate-release form, 4-6 yo]

Dose: 7.5-9 mg/kg/day PO/IV divided bid-tid; Start: 5 mg/kg/day PO/IV divided bid; Info: adjust dose based on tx response and serum levels; if divided doses unequal, give larger dose qhs; taper dose gradually to D/C

[immediate-release form, 7-9 yo]

Dose: 7-8 mg/kg/day PO/IV divided bid-tid; Start: 5 mg/kg/day PO/IV divided bid-tid; Info: adjust dose based on tx response and serum levels; if divided doses unequal, give larger dose qhs; taper dose gradually to D/C

[immediate-release form, 10-16 yo]

Dose: 6-7 mg/kg/day PO/IV divided bid-tid; Start: 5 mg/kg/day PO/IV divided bid-tid; Info: adjust dose based on tx response and serum levels; if divided doses unequal, give larger dose qhs; taper dose gradually to D/C

[immediate-release form, >16 yo]

see Adult Dosing

[extended-release form, 7-9 yo]

Dose: 7-8 mg/kg/day ER PO divided bid-tid; Start: 5 mg/kg/day ER PO divided bid-tid; Info: adjust dose based on tx response and serum levels; if divided doses unequal, give larger dose qhs; if stable on bid-tid ER dosing, then may switch to qd ER dosing; do not open ER cap; taper dose gradually to D/C

[extended-release form, 10-16 yo]

Dose: 6-7 mg/kg/day ER PO divided bid-tid; Start: 5 mg/kg/day ER PO divided bid-tid; Info: adjust dose based on tx response and serum levels; if divided doses unequal, give larger dose qhs; if stable on bid-tid ER dosing, then may switch to qd ER dosing; do not open ER cap; taper dose gradually to D/C

[extended-release form, >16 yo]

see Adult Dosing

Renal dosing

[see below]

renal impairment: no adjustment; Info: do not give oral loading regimen

HD/PD: no adjustment; no supplement; Info: do not give oral loading regimen

Hepatic dosing

[adjust dose amount]

hepatic impairment: decr. dose, amount not defined

SRC: NLM .