Dilantin (phenytoin) is a brand-name drug prescribed for seizures in adults and children. Dilantin comes as an extended-release oral capsule, chewable tablet, and oral liquid. The dosage can vary depending on the drug form.

Dilantin is approved by the Food and Drug Administration (FDA) in adults and children to:

Dilantin belongs to a drug class called antiepileptics and is available in a generic version.

Keep reading for specific information about the Dilantin dosage for seizures, including its strengths and how to take the medication. For an in-depth look at Dilantin, see this article.

Note: This article describes typical dosages of Dilantin for adults and children provided by the drug’s manufacturer. When taking Dilantin, always follow the dosage prescribed by your doctor.

Below is information about Dilantin’s forms, strengths, and dosages.

Dilantin forms and strengths

Dilantin comes in the following forms and strengths:

  • extended-release (ER) oral capsule, which means the drug is slowly released into your body over time:
    • 30 milligrams (mg)
    • 100 mg
  • chewable tablet: 50 mg
  • oral suspension (type of liquid mixture): 125 mg per 5 milliliters (mL) of suspension (5 mg/mL)

Typical dosages

Typically, your doctor will start by prescribing a low dosage. Then, they’ll adjust it over time to reach the amount that’s right for you. Your doctor will ultimately prescribe the smallest dosage that provides the desired effect.

The following information describes the commonly prescribed Dilantin dosage for adults. However, be sure to take the dosage your doctor prescribes for you. Your doctor will determine the best dosage to fit your needs. In some cases, doctors may adjust your dosage from those shown below.

Dilantin dosage for seizures in adults

Doctors may prescribe Dilantin to treat seizures. The dosage can vary depending on the form of the drug prescribed, as follows:

  • Dilantin ER capsule: Your starting dose will likely be 100 mg. The typically recommended dosage of Dilantin for seizures is 100 mg three to four times per day. The maximum recommended dosage is 200 mg three times per day.
  • Dilantin chewable tablet: Your starting dose will likely be 100 mg (two 50 mg tablets). The typically recommended dosage of Dilantin for seizures is 100 mg three to four times per day. The maximum recommended dosage is 200 mg three times per day.
  • Dilantin liquid suspension: Your starting dose will likely be 125 mg (5 mL). Typically, you’ll take this three times per day. The maximum recommended dosage of Dilantin suspension is 625 mg (25 mL) per day.

For more information about your specific dosage, talk with your doctor.

Children’s dosage

Dilantin is approved to treat seizures in children.

The dosage is based on body weight in kilograms (kg). One kg equals about 2.2 pounds (lb). The dose per kg of body weight is measured in milligrams per kilogram (mg/kg) and is calculated by your child’s doctor.

Below is the typical dosing schedule for children taking Dilantin:

  • Starting dosage: 5 mg/kg per day, divided into 2 or 3 doses
  • Maintenance dosage: 4 to 8 mg/kg per day, divided into 2 or 3 doses
  • Maximum dosage: 300 mg per day

For example, if your child weighs 30 kg (about 66 lb), their doctor will likely prescribe a starting dosage of 150 mg per day. Your doctor will have you divide this into two doses of 75 mg each or three doses of 50 mg each.

Talk with your child’s doctor if you have questions about their dosage.

How to take Dilantin

Always follow your doctor’s instructions for taking Dilantin. Here is some general guidance for how to take the different forms:

  • Dilantin ER capsule: You’ll swallow the capsule whole. Do not divide, crush, or chew it. (If you have trouble swallowing capsules, see this article for tips on how to take this form of medication.)
  • Dilantin chewable tablet: You’ll chew the tablet thoroughly and swallow. You may swallow the tablet whole if preferred.
  • Dilantin liquid suspension: Before you measure each dose, shake the container to mix the ingredients. Your pharmacist can give you an oral syringe or medicine cup to measure your prescribed dose. Do not use a household spoon because it isn’t accurate enough. You should store the liquid at room temperature, which is between 68°F and 77°F (20°C and 25°C).

You can take your Dilantin dose with or without food. It may be helpful to take Dilantin around the same time of day. This helps maintain a steady level of the drug in your body so Dilantin can work effectively.

If you have questions about how to take Dilantin, talk with your doctor or pharmacist.

Long-term treatment

Dilantin is meant to be a long-term treatment. If you and your doctor determine that Dilantin is safe and effective for you, you’ll likely take it long term.

Before you start taking Dilantin, your doctor will discuss your treatment plan with you.

Talk with your doctor if you have questions about how long you can expect to take Dilantin.

ACCESSIBLE DRUG LABELS AND CONTAINERS

Some pharmacies offer labels with large print, braille, or a code you scan with a smartphone to convert text to speech. If your local pharmacy doesn’t have these options, your doctor or pharmacist might be able to recommend a pharmacy that does.

If you’re having trouble opening medication bottles, ask your pharmacist about putting Dilantin in an easy-open container. They also may recommend tools that can make it easier to open bottles.

It’s important that you do not take more Dilantin than your doctor prescribes. For some medications, taking more than the recommended amount may lead to harmful effects or overdose.

Symptoms of an overdose

Overdose symptoms of Dilantin can include:

  • blurred vision
  • lethargy (deep sleepiness or difficulty waking)
  • nausea or vomiting
  • eye movements that you can’t control
  • overactive reflexes
  • problems coordinating movements, such as walking
  • tremors
  • trouble speaking or slurred speech

In severe cases, Dilantin overdose can result in coma.

If you take more than the recommended amount of Dilantin

Call your doctor right away if you believe you’ve taken too much Dilantin. Another option is to call America’s Poison Centers at 800-222-1222 or use its online tool. If you have severe symptoms, immediately call 911 or your local emergency number or go to the nearest emergency room.

If you’d like to learn about seizures and related conditions, see our epilepsy and seizures hub.

Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.