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DILANTIN® Extended Oral Capsules Highlights (phenytoin)


These highlights do not include all the information needed to use DILANTIN® safely and effectively. See full prescribing information for DILANTIN®.

DILANTIN® (extended phenytoin sodium capsules), for oral use
Initial U.S. Approval: 1953


Warnings and Precautions (5.3)2/2021


DILANTIN is indicated for the treatment of tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures and prevention and treatment of seizures occurring during or following neurosurgery. (1)


  • Adult starting dose in patients who have received no previous treatment is one 100 mg DILANTIN extended capsule three times a day, with dose adjustments as necessary. For most adults, the satisfactory maintenance dose will be one capsule three to four times a day. An increase, up to two capsules three times a day may be made, if necessary. (2.1)
  • Adult once-a-day dose: If seizure control is established with divided doses of three 100 mg DILANTIN extended capsules daily, once-a-day dosage with 300 mg DILANTIN extended capsules may be considered. (2.1)
  • Adult loading dose: reserved for patients in a clinic or hospital setting who require rapid steady-state serum levels and where intravenous administration is not desired. Refer to full prescribing information. (2.1)
  • Pediatric starting dose is 5 mg/kg/day in two to three equally divided doses, with dosage adjustments as necessary, up to a maximum of 300 mg daily. Maintenance dosage is 4 to 8 mg/kg/day. (2.2)
  • Serum blood level determinations may be necessary for optimal dosage adjustments—the clinically effective serum total concentration is 10 to 20 mcg/mL (unbound phenytoin concentration is 1 to 2 mcg/mL). (2.3)


DILANTIN is available as 30 mg and 100 mg extended phenytoin sodium capsules. (3)


  • Hypersensitivity to phenytoin, its ingredients, or other hydantoins (4, 5.5)
  • A history of prior acute hepatotoxicity attributable to phenytoin (4, 5.8)
  • Coadministration with delavirdine (4)


  • Withdrawal Precipitated Seizure: May precipitate status epilepticus. Dose reductions or discontinuation should be done gradually. (5.1)
  • Suicidal Behavior and Ideation: Monitor patients for the emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior. (5.2)
  • Serious Dermatologic Reactions: Discontinue DILANTIN at the first sign of a rash, unless the rash is clearly not drug-related. If signs or symptoms suggest SJS/TEN, use of this drug should not be resumed and alternative therapy should be considered. (5.3)
  • Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity: If signs or symptoms of hypersensitivity are present, evaluate the patient immediately. Discontinue if an alternative etiology cannot be established. (5.4)
  • Cardiac Effects: Bradycardia and cardiac arrest have been reported. (5.6)
  • Angioedema: Discontinue immediately if symptoms of angioedema such as facial, perioral, or upper airway swelling occur. (5.7)
  • Hepatic Injury: Cases of acute hepatotoxicity have been reported with DILANTIN. If this occurs, immediately discontinue. (4, 5.8)
  • Hematopoietic Complications: If occurs, follow-up observation is indicated and an alternative antiepileptic treatment should be used. (5.9)


The most common adverse reactions are nervous system reactions, including nystagmus, ataxia, slurred speech, decreased coordination, somnolence, and mental confusion. (6)

To report SUSPECTED ADVERSE REACTIONS, contact Pfizer, Inc. at 1-800-438-1985 or FDA at 1-800-FDA-1088 or


Multiple drug interactions because of extensive plasma protein binding, saturable metabolism and potent induction of hepatic enzymes. (7.1, 7.2)


  • Pregnancy: Prenatal exposure to phenytoin may increase the risks for congenital malformations and other adverse developmental outcomes. (5.13, 8.1)
  • Renal and/or Hepatic Impairment or Hypoalbuminemia: Monitor unbound phenytoin concentrations in these patients. (8.6)

See 17 for PATIENT COUNSELING INFORMATION and Medication Guide.

Revised: 3/2021

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