phenytoin, Dilantin, Dilantin-125
Omudhome Ogbru, PharmD
Omudhome Ogbru, PharmD
Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.
Medical and Pharmacy Editor:
GENERIC NAME: phenytoin
BRAND NAME: Dilantin, Dilantin-125
DRUG CLASS AND MECHANISM: Phenytoin is an oral and injectable anti-seizure medication first synthesized in 1908. The exact mechanism of action is not known, Phenytoin may work by reducing the sensitivity of nerves in the brain to excessive stimulation and reducing transmission of impulses between nerves. Phenytoin was originally approved by the FDA in 1939.
GENERIC AVAILABLE: Yes
PREPARATIONS: Capsules (extended or immediate release): 30, 100, 200, and 300 mg; Chewable Tablet: 50 mg; Suspension: 125 mg/5 mL; Injection: 50 mg/mL.
STORAGE: Capsules, tablets, and suspension should be kept at room temperature, 68-77 F (20-25 C).
PRESCRIBED FOR: Phenytoin is an anti-seizure medication (anticonvulsant) used for preventing or treating generalized tonic-clonic (grand mal) seizures, complex partial seizures (psychomotor seizures), and seizures occurring during or after neurosurgery. It may be used alone or with phenobarbital or other anticonvulsants.
DOSING: The dosing of phenytoin is patient specific. It may be given once, twice, 3, or 4 times daily. Doses are often adjusted to find the optimal dose based on measurement of blood levels. Taking phenytoin with food may reduce some of the side effects. Elderly patients, debilitated persons, and patients with certain kidney or liver diseases may need lower doses. The suspension should not be given at the same time as tube feedings since tube feedings bind to phenytoin and reduce its absorption. The recommended adult dose is 100 mg two to four times daily. Some patients may require 200 mg three times daily. Patients stabilized on 100 mg three times daily may receive 300 mg once daily of the extended release capsules.
DRUG INTERACTIONS: There are many potential drug interactions with phenytoin. Phenytoin can increase the metabolism (elimination) of many drugs, reducing their concentrations in the body. Drugs that may be affected include:
Phenytoin can interact with these drugs not only when it is added to therapy but also when it is discontinued. In the latter case, the concentration of the other drugs may increase. Sometimes the effect may be unpredictable. Phenytoin's metabolism may be affected by other drugs. Drugs that increase phenytoin blood levels and toxicity include:
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