Phenytoin
Generic Name: phenytoin
Brand Names:
Phenytoin
11 DESCRIPTION Phenytoin is related to the barbiturates in chemical structure, but has a five-membered ring. The chemical name is 5,5-diphenyl-2,4 imidazolidinedione, having the following structural formula: Each phenytoin chewable tablet, USP for oral administration, contains 50 mg phenytoin, USP. Also contains: Artificial banana flavor, compressible sugar, D&C yellow No. 10 aluminum lake, FD&C yellow No.
Overview
11 DESCRIPTION Phenytoin is related to the barbiturates in chemical structure, but has a five-membered ring. The chemical name is 5,5-diphenyl-2,4 imidazolidinedione, having the following structural formula: Each phenytoin chewable tablet, USP for oral administration, contains 50 mg phenytoin, USP. Also contains: Artificial banana flavor, compressible sugar, D&C yellow No. 10 aluminum lake, FD&C yellow No.
Uses
1 INDICATIONS AND USAGE Phenytoin chewable tablets are indicated for the treatment of generalized tonic-clonic (grand mal) and complex partial (psychomotor, temporal lobe) seizures and prevention and treatment of seizures occurring during or following neurosurgery. Phenytoin chewable tablets are indicated for the treatment of generalized tonic-clonic (grand mal) and complex partial (psychomotor, temporal lobe) seizures and prevention and treatment of seizures occurring during or following neurosurgery. (1)
Dosage
2 DOSAGE AND ADMINISTRATION NOT FOR ONCE-A-DAY DOSING ( 2.1 ) Adult starting dose in patients who have received no previous treatment is two phenytoin chewable tablets three times a day, with dose adjustments as necessary. For most adults, the satisfactory maintenance dose will be six to eight phenytoin chewable tablets daily; an increase to twelve phenytoin chewable tablets daily may be made, if necessary. ( 2.2 ) 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 mg/kg/day to 8 mg/kg/day.
Side Effects
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)...
Interactions
7 DRUG INTERACTIONS Phenytoin is extensively bound to plasma proteins and is prone to competitive displacement. Phenytoin is primarily metabolized by the hepatic cytochrome P450 enzyme CYP2C9 and to a lesser extent by CYP2C19, and is particularly susceptible to inhibitory drug interactions because it is subject to saturable metabolism. Inhibition of metabolism may produce significant increases in circulating phenytoin concentrations and enhance the risk of drug toxicity. Monitoring of phenytoin serum levels is recommended when a drug interaction is suspected. Phenytoin is a potent inducer of hepatic drug-metabolizing enzymes. Multiple drug interactions because of extensive plasma protein binding, saturable metabolism and potent induction of hepatic enzymes.
Warnings
5 WARNINGS AND PRECAUTIONS 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 phenytoin chewable tablets 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. 4 CONTRAINDICATIONS Phenytoin chewable tablets are 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) ] .
Pregnancy
8.1 Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to antiepileptic drugs (AEDs), such as phenytoin, during pregnancy. Physicians are advised to recommend that pregnant patients taking phenytoin enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry. This can be done by calling the toll free number 1-888-233-2334, and must be done by patients themselves. Information on the registry can also be found at the website http://www.aedpregnancyregistry.org/.
Storage
16.2 Storage and Handling Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature]. Protect from moisture.
Frequently Asked Questions
What is Phenytoin used for?▼
1 INDICATIONS AND USAGE Phenytoin chewable tablets are indicated for the treatment of generalized tonic-clonic (grand mal) and complex partial (psychomotor, temporal lobe) seizures and prevention and treatment of seizures occurring during or following neurosurgery. Phenytoin chewable tablets are indicated for the treatment of generalized tonic-clonic (grand mal) and complex partial (psychomotor, temporal lobe) seizures and prevention and treatment of seizures occurring during or following neurosurgery. (1)
What are the side effects of Phenytoin?▼
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)...
Can I take Phenytoin during pregnancy?▼
8.1 Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to antiepileptic drugs (AEDs), such as phenytoin, during pregnancy. Physicians are advised to recommend that pregnant patients taking phenytoin enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry. This can be done by calling the toll free number 1-888-233-2334, and must be done by patients themselves. Information on the registry can also be found at the website http://www.aedpregnancyregistry.org/.
What are the important warnings for Phenytoin?▼
5 WARNINGS AND PRECAUTIONS 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 phenytoin chewable tablets 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. 4 CONTRAINDICATIONS Phenytoin chewable tablets are 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) ] .
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Medical Disclaimer
This drug information is for educational purposes only and should not replace professional medical advice. Drug information is sourced from the FDA National Drug Code Directory and Structured Product Labeling. Always consult with a healthcare provider before starting, stopping, or changing any medication.