DILANTIN

Product Type: HUMAN PRESCRIPTION DRUG

Route: ORAL

Dosage Form:

NDC: 58151-110

Application: ANDA084349

Effective: 20230821

1 INDICATIONS AND USAGE 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. 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 )

2 DOSAGE AND ADMINISTRATION • 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 ) 2.1 Adult Dosage Divided Daily Dosage: The recommended starting dose for adult patients who have received no previous treatment is one 100-mg DILANTIN (extended phenytoin sodium capsule, USP) by mouth three times daily. Adjust the dosage to suit individual requirements up to a maximum of two capsules three times a day. For most adults, the satisfactory maintenance dosage will be one capsule three to four times a day. Once-a-day Dosage: In adults, if seizure control is established with divided doses of three 100-mg DILANTIN (extended phenytoin sodium capsules, USP) daily, once-a-day dosage with 300 mg of DILANTIN (extended phenytoin sodium capsules, USP) may be considered. Studies comparing divided doses of 300 mg with a single daily dose of this quantity indicated absorption, peak serum levels, biologic half-life, difference between peak and minimum values, and urinary recovery were equivalent. Once-a-day dosage offers a convenience to the individual patient or to nursing personnel for institutionalized patients and is intended to be used only for patients requiring this amount of drug daily. A major problem in motivating noncompliant patients may also be lessened when the patient can take this drug once a day. However, patients should be cautioned not to miss a dose, inadvertently. Only DILANTIN (extended phenytoin sodium capsules, USP) are recommended for once-a-day dosing. Inherent differences in dissolution characteristics and resultant absorption rates of phenytoin due to different manufacturing procedures and/or dosage forms preclude such recommendation for other phenytoin products. When a change in the dosage form or brand is prescribed, careful monitoring of phenytoin serum levels should be carried out. Loading Dose: Some authorities have advocated use of an oral loading dose of phenytoin in adults who require rapid steady-state serum levels and where intravenous administration is not desirable. This dosing regimen should be reserved for patients in a clinic or hospital setting where phenytoin serum levels can be closely monitored. Patients with a history of renal or liver disease should not receive the oral loading regimen. Initially, one gram of DILANTIN (extended phenytoin sodium capsules, USP) is divided into three doses (400 mg, 300 mg, 300 mg) and administered at two-hour intervals. Normal maintenance dosage is then instituted 24 hours after the loading dose, with frequent serum level determinations. 2.2 Pediatric Dosage The recommended starting dosage for pediatric patients is 5 mg/kg/day by mouth in two or three equally divided doses, with subsequent dosage individualized to a maximum of 300 mg daily in divided doses. A recommended daily maintenance dosage is usually 4 to 8 mg/kg/day in equally divided doses. Children over 6 years and adolescents may require the minimum adult dosage (300 mg/day). 2.3 Dosage Adjustments Dosage should be individualized to provide maximum benefit. In some cases, serum blood level determinations may be necessary for optimal dosage adjustments. Trough levels provide information about clinically effective serum level range and confirm patient compliance, and are obtained just prior to the patient’s next scheduled dose. Peak levels indicate an individual’s threshold for emergence of dose-related side effects and are obtained at the time of expected peak concentration. Therapeutic effect without clinical signs of toxicity occurs more often with serum total concentrations between 10 and 20 mcg/mL (unbound phenytoin concentrations between 1 and 2 mcg/mL), although some mild cases of tonic-clonic (grand mal) epilepsy may be controlled with lower serum levels of phenytoin. In patients with renal or hepatic disease, or in those with hypoalbuminemia, the monitoring of unbound phenytoin concentrations may be more relevant [see Dosage and Administration (2.5) ] . With recommended dosage, a period of seven to ten days may be required to achieve steady-state blood levels with phenytoin and changes in dosage (increase or decrease) should not be carried out at intervals shorter than seven to ten days. 2.4 Switching Between Phenytoin Formulations The free acid form of phenytoin is used in DILANTIN-125 Suspension and DILANTIN Infatabs. DILANTIN extended capsules and parenteral DILANTIN are formulated with the sodium salt of phenytoin. Because there is approximately an 8% increase in drug content with the free acid form over that of the sodium salt, dosage adjustments and serum level monitoring may be necessary when switching from a product formulated with the free acid to a product formulated with the sodium salt and vice versa. 2.5 Dosing in Patients with Renal or Hepatic Impairment or Hypoalbuminemia Because the fraction of unbound phenytoin is increased in patients with renal or hepatic disease, or in those with hypoalbuminemia, the monitoring of phenytoin serum levels should be based on the unbound fraction in those patients [see Warnings and Precautions (5.11) and Use in Specific Populations (8.6) ] . 2.6 Geriatric Dosage Phenytoin clearance is decreased slightly in elderly patients and lower or less frequent dosing may be required [see Clinical Pharmacology (12.3) ] . 2.7 Dosing During Pregnancy Decreased serum concentrations of phenytoin may occur during pregnancy because of altered phenytoin pharmacokinetics. Periodic measurement of serum phenytoin concentrations should be performed during pregnancy, and the DILANTIN dosage should be adjusted as necessary. Postpartum restoration of the original dosage will probably be indicated [see Use in Specific Populations (8.1) ] . Because of potential changes in protein binding during pregnancy, the monitoring of phenytoin serum levels should be based on the unbound fraction.

4 CONTRAINDICATIONS DILANTIN is contraindicated in patients with: • A history of hypersensitivity to phenytoin, its inactive ingredients, or other hydantoins [see Warnings and Precautions (5.5) ] . Reactions have included angioedema. • A history of prior acute hepatotoxicity attributable to phenytoin [see Warnings and Precautions (5.8) ] . • Coadministration with delavirdine because of the potential for loss of virologic response and possible resistance to delavirdine or to the class of non-nucleoside reverse transcriptase inhibitors. • 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 )

Not available.

6 ADVERSE REACTIONS The following serious adverse reactions are described elsewhere in the labeling: • Withdrawal Precipitated Seizure, Status Epilepticus [see Warnings and Precautions (5.1) ] • Suicidal Behavior and Ideation [see Warnings and Precautions (5.2) ] • Serious Dermatologic Reactions [see Warnings and Precautions (5.3) ] • Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity [see Warnings and Precautions (5.4) ] • Hypersensitivity [see Warnings and Precautions (5.5) ] • Cardiac Effects [see Warnings and Precautions (5.6) ] • Angioedema [see Warnings and Precautions (5.7) ] • Hepatic Injury [see Warnings and Precautions (5.8) ] • Hematopoietic Complications [see Warnings and Precautions (5.9) ] • Effects on Vitamin D and Bone [see Warnings and Precautions (5.10) ] • Exacerbation of Porphyria [see Warnings and Precautions (5.12) ] • Teratogenicity and Other Harm to the Newborn [see Warnings and Precautions (5.13) ] • Hyperglycemia [see Warnings and Precautions (5.14) ] The following adverse reactions associated with the use of DILANTIN were identified in clinical studies or postmarketing reports. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Body as a Whole: Allergic reactions in the form of rash and rarely more serious forms and DRESS have been observed, as has angioedema [see Warnings and Precautions (5.3 , 5.4 , 5.7) ] . Anaphylaxis has also been reported. There have also been reports of coarsening of facial features, systemic lupus erythematosus, periarteritis nodosa, and immunoglobulin abnormalities. Digestive System: Acute hepatic failure, toxic hepatitis, liver damage, nausea, vomiting, constipation, enlargement of the lips, and gingival hyperplasia. Hematologic and Lymphatic System: Hematopoietic complications, some fatal, have occasionally been reported in association with administration of phenytoin. These have included thrombocytopenia, leukopenia, granulocytopenia, agranulocytosis, and pancytopenia with or without bone marrow suppression. While macrocytosis and megaloblastic anemia have occurred, these conditions usually respond to folic acid therapy. Lymphadenopathy including benign lymph node hyperplasia, pseudolymphoma, lymphoma, and Hodgkin’s disease have been reported [see Warnings and Precautions (5.9) ] . Pure red cell aplasia has also been reported. Laboratory Test Abnormality: Phenytoin may decrease serum concentrations of thyroid hormone (T4 and T3), sometimes with an accompanying increase in thyroid-stimulating hormone (TSH), but usually in the absence of clinical hypothyroidism. Phenytoin may also produce lower than normal values for dexamethasone or metyrapone tests. Phenytoin may cause increased serum levels of glucose [see Warnings and Precautions (5.14) ] , alkaline phosphatase, and gamma glutamyl transpeptidase (GGT). Nervous System: The most common adverse reactions encountered with phenytoin therapy are nervous system reactions and are usually dose-related. Reactions include nystagmus, ataxia, slurred speech, decreased coordination, somnolence, and mental confusion. Dizziness, vertigo, insomnia, transient nervousness, motor twitchings, paresthesias, and headaches have also been observed. There have also been rare reports of phenytoin-induced dyskinesias, including chorea, dystonia, tremor and asterixis, similar to those induced by phenothiazine and other neuroleptic drugs. Cerebellar atrophy has been reported, and appears more likely in settings of elevated phenytoin levels and/or long-term phenytoin use [see Warnings and Precautions (5.15) ] . A predominantly sensory peripheral polyneuropathy has been observed in patients receiving long-term phenytoin therapy. Skin and Appendages: Dermatological manifestations sometimes accompanied by fever have included scarlatiniform or morbilliform rashes. A morbilliform rash (measles-like) is the most common; other types of dermatitis are seen more rarely. Other more serious forms which may be fatal have included bullous, exfoliative or purpuric dermatitis, acute generalized exanthematous pustulosis, Stevens-Johnson syndrome, and toxic epidermal necrolysis [see Warnings and Precautions (5.3) ] . There have also been reports of hypertrichosis and urticaria. Special Senses: Altered taste sensation including metallic taste. Urogenital: Peyronie’s disease. 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 Viatris at 1-877-446-3679 (1-877-4-INFO-RX) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.