Epilepsy Home > Dilantin Dosage

The recommended starting dose of Dilantin for those taking extended-release capsules is 100 mg three times daily or 300 mg once daily. Dosing for the chewable tablets typically starts at 100 mg three times a day. For the oral suspension form, dosing generally starts at 125 mg three times daily. Your healthcare provider will most likely measure the amount of Dilantin in your blood and adjust the amount as necessary.

An Introduction to Dilantin Dosing

The dose of Dilantin® (phenytoin) your healthcare provider recommends will vary, depending on a number of factors, including:
  • The particular Dilantin product
  • Your age and weight
  • The amount of Dilantin in your blood (measured using a blood test)
  • Other medications you may be taking
  • Other medical conditions you may have.
As always, do not adjust this amount unless your healthcare provider specifically instructs you to do so.
It is very important to understand that the different Dilantin products are not interchangeable. Dilantin Kapseals® (capsules) contain phenytoin sodium, while Dilantin Infatabs® (tablets) and oral suspension (liquid) contain phenytoin. These are simply different forms of the same chemical. They work the same way in the body, but the doses are not equivalent. In other words, 100 mg of Dilantin in capsule form is not the same as 100 mg of Dilantin in tablet or suspension form.

Dilantin Dosages for Adults

Refer to the following table for the recommended starting doses for adults.
Dilantin Product
Starting Adult Dosage
Dilantin Kapseals (extended-release capsules)
100 mg three times daily or 300 mg once daily
Dilantin Infatabs (chewable tablets)
100 mg (two tablets) three times daily
Dilantin-125 (oral suspension)
125 mg (5 mL or 1 teaspoonful) three times daily
Most likely, your healthcare provider will measure the amount of Dilantin in your blood (using a blood test) and adjust your dose as necessary. Because it takes a while for the medication to build up in your system, this blood test is most useful 7 to 10 days after starting Dilantin or changing your dosage (when you have reached a steady level). In emergencies, your healthcare provider may start you at a higher amount.
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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