Dilantin (phenytoin) is a prescription drug used for certain types of seizures. Dilantin comes as a liquid suspension, oral capsule, and chewable tablet. Your dosage may vary based on certain factors, such as the form you take.

Dilantin is used in adults and children to:

The active ingredient in Dilantin is phenytoin. Dilantin belongs to a group of drugs called antiepileptics.

This article describes the dosages of Dilantin, as well as its strengths and how to take it. To learn more about Dilantin, see this in-depth article.

This section describes the usual dosages of Dilantin. Keep reading to learn more.

What are Dilantin’s forms?

Dilantin comes in three forms:

  • extended-release* oral capsules
  • oral liquid suspension (a type of liquid mixture)
  • chewable tablets

* “Extended release” means the drug is slowly released into your body over a long period of time.

What strengths does Dilantin come in?

Dilantin comes in the following strengths:

  • oral capsules: 30 milligrams (mg) and 100 mg
  • oral liquid suspension: 125 mg per 5 milliliters (mL)
  • chewable tablets: 50 mg

What are the usual dosages of Dilantin?

The Dilantin dosage your doctor prescribes depends on certain factors. These may include:

  • your age
  • body weight (for children)
  • the form you’re prescribed
  • the level of Dilantin in your blood during treatment

Your doctor will determine the best dosage to fit your needs. In some cases, they may adjust your dosage based on how you respond to treatment and other factors.

Dilantin adult dosage for seizures

The information below describes the typical dosages of Dilantin for adults, depending on the form you’re prescribed. If you have questions about your dosage, talk with your doctor.

Dosage of oral capsules

The typical starting dosage of Dilantin extended-release oral capsules is 100 mg taken three times per day.

Your doctor will likely check your blood levels of Dilantin after 7 to 10 days of treatment. They may adjust your dosage if necessary. The usual maintenance (ongoing) dosage for most adults for Dilantin oral capsules is 100 mg taken three or four times per day. If needed, your doctor may increase your dosage up to a maximum dosage of two capsules taken three times per day.

If your seizures are well managed with a dosage of 100 mg taken three times per day, your doctor may recommend changing to a once-daily dosage of 300 mg (three 100-mg capsules taken at once).

Dosage of oral liquid suspension

The recommended starting dosage for adults with seizures is 125 mg (or 5 mL, which equals 1 teaspoonful) taken three times per day. Your doctor will likely test your blood levels of Dilantin after 7 to 10 days of treatment. They may make dosage adjustments if needed. The maximum daily dosage of the liquid suspension is 25 mL per day.

Dosage of chewable tablets

The typical starting dosage of Dilantin chewable tablets for adults is two Dilantin Infatabs (100 mg) taken three times per day. Your doctor will likely test your blood levels of Dilantin after 7 to 10 days. They may adjust your dosage if needed. The typical maintenance dosage for most adults is six to eight Infatabs daily (300 mg to 400 mg) in divided doses.

The maximum daily dosage of Dilantin Infatabs in adults is 12 tablets (600 mg) divided into equal doses. Your doctor or pharmacist will explain your dosing schedule if you’re prescribed the chewable tablets.

What’s the dosage of Dilantin for children?

Dilantin is used to help treat tonic-clonic seizures and temporal lobe seizures in children. It is also used to prevent and treat seizures that may happen during or after brain surgery

The dosage used in children is based on their body weight in kilograms (kg). For reference, 1 kg is equal to about 2.2 pounds (lb).

The dosage amount of Dilantin used in children is the same for all three forms. But the number of capsules, chewable tablets, or teaspoons of liquid suspension your child takes depends on the form.

The starting dosage of Dilantin in children is 5 mg per kg (mg/kg) per day. The dose is divided into two or three doses per day. Your child’s doctor will likely test your child’s blood levels of Dilantin after 7 to 10 days of treatment. They may then adjust their Dilantin dosage up to a maximum dosage of 300 mg per day.

The usual maintenance (ongoing) dosage in children is 4 mg/kg per day to 8 mg/kg per day.

Note: Your child may need an adult dosage of 300 mg per day if they’re ages 6 to 17 years. Your child’s doctor will discuss the best dosage for your child.

For more information about Dilantin’s dosage for children, talk with your child’s doctor or a pharmacist.

How to take Dilantin

Dilantin comes as an oral capsule, an oral liquid suspension, and a chewable tablet. Follow your doctor’s directions on how to take the form of Dilantin you’re prescribed. You may take Dilantin several times per day, depending on your dosage.

Your doctor may need to adjust your dosage and check your blood levels of Dilantin if you switch from taking the oral capsules to the liquid suspension or chewable tablets, or vice versa. This is because the capsules are an extended-release form of Dilantin, while the suspension and tablets are not.

You should not crush Dilantin oral capsules. Instead, swallow them whole. Crushing the capsules can affect how the medication works. You can chew the Dilantin Infatabs or swallow them whole.

For the liquid suspension form, measure out the exact dosage using a measuring device provided by your doctor or pharmacist. Do not use a household teaspoon to measure the dose.

If you have questions or concerns about taking the form of Dilantin you’ve been prescribed, talk with your doctor.

Is Dilantin used long term?

It’s possible. Dilantin is typically used as a long-term treatment for types of tonic-clonic seizures and temporal lobe seizures. If you’re prescribed Dilantin to treat or prevent seizures during and after brain surgery, your doctor will let you know how long you’ll likely need to take the drug.

If you have questions about how long your Dilantin treatment will last, talk with your doctor or pharmacist.

Do not take more Dilantin than your doctor prescribes, as this can lead to harmful effects.

Symptoms of overdose

Symptoms caused by an overdose of Dilantin can include:

In some cases, overdose of Dilantin can also lead to coma.

What to do in case you take too much Dilantin

Call your doctor right away if you think you’ve taken too much Dilantin. You can also call 800-222-1222 to reach America’s Poison Centers or use its online resources. But if you have severe symptoms, immediately call 911 (or your local emergency number) or go to the nearest emergency room.

Disclaimer: Healthline 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.