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Understanding Dilantin: A Comprehensive Guide for Physicians

Updated: May 23



Patient on IV (cannot take oral)

Dilantin 100 mg IV every 8 hours

Patient can eat soft/regular diet

Dilantin 100 mg orally three times a day (postprandial)

Patient on IV and enteral feeding

Dilantin 50 mg orally twice three times a day with feeds


Dilantin, also known by its generic name phenytoin, is a cornerstone in the management of seizure disorders. As a physician, it’s crucial to have a deep understanding of its dosage, administration, mechanism of action, and patient education strategies. This blog will provide an in-depth look at these aspects to ensure optimal patient care.

Dosage and Administration Adult Patients

For adults, the initial dose of Dilantin is typically 100 mg taken three times daily. Maintenance doses usually range from 300 mg to 400 mg per day, divided into one to three doses. Some patients may require higher doses to achieve therapeutic levels, which generally range from 10-20 mcg/mL.

Pediatric Patients

In children, dosages are often calculated based on body weight, at approximately 5 mg/kg/day, not exceeding 300 mg per day. The total daily dose is divided into two or three administrations.

Key Teaching Points for Patients

Educating patients on the proper use of Dilantin is critical for effective seizure management and minimizing adverse effects. Here are essential points to cover:

  1. Medication Adherence:

  • Stress the importance of taking Dilantin exactly as prescribed.

  • Warn against abrupt discontinuation, which can precipitate seizures.

  1. Administration Guidelines:

  • Can be taken with or without food but should be consistent each time.

  • For liquid forms, use a proper measuring device.

  • Do not crush or chew extended-release capsules.

  1. Monitoring for Side Effects:

  • Common side effects include dizziness, drowsiness, nausea, and vomiting.

  • Serious adverse effects to watch for include rash, hepatic dysfunction, and hematologic abnormalities.

  • Advise patients to report signs of allergic reactions, unusual bruising, or jaundice immediately.

  1. Drug Interactions:

  • Dilantin interacts with various medications, including other anticonvulsants, anticoagulants, and certain antibiotics.

  • Ensure patients maintain an updated list of all medications and supplements for review.

  1. Regular Monitoring:

  • Periodic blood tests are necessary to monitor serum phenytoin levels and ensure they stay within the therapeutic range.

  • Liver function tests and complete blood counts are also recommended.

  1. Oral Hygiene:

  • Phenytoin can cause gingival hyperplasia.

  • Encourage patients to practice good oral hygiene and schedule regular dental check-ups.

Mechanism of Action

Phenytoin’s efficacy in seizure control is primarily due to its action on voltage-gated sodium channels in neuronal membranes. By blocking these channels, phenytoin slows their recovery from the inactivated state to the closed state. This delay prevents the rapid, repetitive firing of action potentials that characterizes seizures.

Additionally, phenytoin reduces synaptic transmission by limiting the spread of seizure activity across neuronal networks. This stabilization of neuronal membranes is key to its anticonvulsant properties.


Dilantin remains a vital medication in the management of seizure disorders. By understanding its proper use, mechanism of action, and key points for patient education, physicians can enhance treatment outcomes and ensure patient safety. Regular monitoring and patient engagement are essential components of successful long-term seizure management.


  1. Dilantin (Phenytoin) Prescribing Information. Accessed on [19/5/2024 ].

  2. Guidelines for the Management of Epilepsy. American Epilepsy Society. [19/5/2024]

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