Dilantin (phenytoin) is a prescription drug used in adults and children with certain types of seizures. Dilantin can interact with alcohol, other medications, and some supplements. For example, it can interact with other seizure drugs and antacids.

Dilantin comes as a chewable tablet, an oral suspension (a type of liquid mixture), and an extended-release oral capsule. (“Extended release” means the drug is slowly released into your body over a long period of time.) The drug’s active ingredient is phenytoin.

An interaction can occur because one substance causes another substance to have a different effect than expected. Interactions can also occur if you have certain health conditions.

Keep reading to learn about Dilantin’s possible interactions. And for more information about Dilantin, including details about its uses, see this article.

Before you start taking Dilantin, tell your doctor and pharmacist about any prescription, over-the-counter, or other drugs you take. Sharing this information with them may help prevent possible interactions. (To learn whether Dilantin interacts with herbs or vitamins and supplements, see the “Are there other interactions with Dilantin?” section below.)

If you have questions about drug interactions that may affect you, talk with your doctor or pharmacist.

The table below lists drugs that may interact with Dilantin. Keep in mind that this table does not include all drugs that may interact with Dilantin. For more information about some of these interactions, see the “Drug interactions explained” section below.

Drug group or drug nameDrug examplesWhat can happen
other seizure drugs • carbamazepine (Carbatrol, Tegretol, others)
• ethosuximide (Zarontin)
lamotrigine (Lamictal, Lamictal XR)
• oxcarbazepine (Oxtellar XR, Trileptal)
• topiramate (Qudexy XR, Trokendi XR, others)
could make either drug less effective or raise the risk of side effects from Dilantin
antacids• aluminum hydroxide/magnesium hydroxide (Maalox)
• calcium carbonate (TUMS)
• calcium carbonate/magnesium hydroxide (Rolaids)
could make Dilantin less effective
birth control pills• ethinyl estradiol/desogestrel (Enskyce, Kariva, others)
• ethinyl estradiol/levonorgestrel (Seasonale, Seasonique, others)
• norgestrel (Opill)
could make the birth control pill less effective
blood thinners• apixaban (Eliquis)
• dabigatran (Pradaxa)
• edoxaban (Savaysa)
• rivaroxaban (Xarelto)
• warfarin (Jantoven)
could raise your risk of side effects from the blood thinner or make it less effective
corticosteroids• methylprednisolone (Medrol)
• prednisolone (Omnipred, Prelone, others)
prednisone (Rayos)
may make the corticosteroid less effective
certain antibiotics• ciprofloxacin (Cipro)
clarithromycin
• clindamycin (Cleocin)
• sulfamethoxazole/
trimethoprim (Bactrim, Septra, others)
could make either drug less effective or raise the risk of side effects from Dilantin
certain selective serotonin reuptake inhibitors (SSRIs)• fluoxetine (Prozac)
• fluvoxamine (Luvox)
paroxetine (Brisdelle, Paxil, others)
• sertraline (Zoloft)
could raise the risk of side effects from Dilantin or make the SSRI less effective
certain proton pump inhibitors (PPIs)• dexlansoprazole (Dexilant)
• esomeprazole (Nexium)
• omeprazole (Prilosec)
could raise the risk of side effects from Dilantin or make the PPI less effective
certain statins• atorvastatin (Atorvaliq, Lipitor)
• fluvastatin (Lescol XL)
• lovastatin (Altoprev)
• simvastatin (FloLipid, Zocor)
may make the statin less effective
ticagrelor (Brilinta)could make ticagrelor less effective

Certain health conditions or other factors could raise your risk of harm if you take Dilantin. In such cases, your doctor may not prescribe Dilantin for you. These are known as contraindications. The list below includes Dilantin’s contraindications.

If you’ve had a liver problem with phenytoin: If you’ve had a liver problem while taking phenytoin before, your doctor likely won’t prescribe Dilantin for you. Phenytoin is the active ingredient in Dilantin, so taking Dilantin could lead to the same liver problem.

Before taking Dilantin, tell your doctor if you’ve had a liver problem while taking phenytoin. They can recommend an alternative to Dilantin.

If you’ve had an allergic reaction: If you’ve had an allergic reaction to Dilantin or any of its ingredients, your doctor likely won’t prescribe Dilantin for you. This is because taking the drug could cause another allergic reaction. You can ask your doctor about other treatments that may be better options for you.

Before you start taking Dilantin, talk with your doctor if either of the factors above applies to you. Your doctor can determine whether Dilantin is safe for you to take.

It’s not safe to consume alcohol during your Dilantin treatment. Doing so can affect how well Dilantin works for seizures.

Dilantin and alcohol can also cause some similar side effects, such as dizziness and confusion. Combining alcohol and Dilantin could raise your risk of having these side effects or could worsen them.

If you have questions about avoiding alcohol while taking Dilantin, talk with your doctor or pharmacist.

Learn more about certain drug interactions that can occur with Dilantin.

Interaction with other seizure drugs

Dilantin can interact with other drugs that are used to treat seizures.

Examples of other seizure medications include:

  • carbamazepine (Carbatrol, Tegretol, others)
  • ethosuximide (Zarontin)
  • lamotrigine (Lamictal, Lamictal XR)
  • oxcarbazepine (Oxtellar XR, Trileptal)
  • topiramate (Qudexy XR, Trokendi XR, others)

What could happen

The outcome of an interaction between Dilantin and another seizure drug depends on the specific drug.

For example, taking Dilantin with certain seizure drugs may cause your body to break down either drug more quickly than it should. This can lower the level of either drug in your body, which could make that drug less effective.

However, taking Dilantin with other types of seizure drugs may cause your body to break down Dilantin more slowly than usual. This can lead to high levels of Dilantin in your system, which could increase your risk of side effects.

What you can do

Doctors may prescribe Dilantin with other seizure drugs, even those that it interacts with.

If you take Dilantin with another seizure drug, your doctor may adjust your dosage of either medication. This helps make sure the level of the drug in your body is high enough to treat your condition without raising your risk of side effects. You should not take a higher dose of either medication than your doctor prescribes.

If you have questions about taking Dilantin with other seizure drugs, talk with your doctor or pharmacist.

Interaction with antacids

Dilantin can interact with antacids, which are used to treat conditions such as heartburn and indigestion.

Examples of antacids include:

  • aluminum hydroxide/magnesium hydroxide (Maalox)
  • calcium carbonate (TUMS)
  • calcium carbonate/magnesium hydroxide (Rolaids)

What could happen

Dilantin may be less effective if taken with antacids. Antacids may prevent your body from absorbing Dilantin. This may lead to low levels of Dilantin in your system, preventing the drug from working as well as it should.

What you can do

If you have heartburn or indigestion while you’re taking Dilantin, talk with your doctor. They may advise you to avoid antacids. Instead, your doctor can recommend other options for easing your symptoms.

If you have questions about taking Dilantin with antacids, talk with your doctor or pharmacist.

Interaction with birth control pills

Dilantin can interact with birth control pills, which are used to help prevent pregnancy.

Examples of birth control pills include:

  • ethinyl estradiol/desogestrel (Enskyce, Kariva, others)
  • ethinyl estradiol/levonorgestrel (Seasonale, Seasonique, others)
  • norgestrel (Opill)

What could happen

Birth control pills may be less effective if taken with Dilantin. This is because Dilantin can cause your body to break down the active ingredients in birth control more quickly than usual. This can lead to low levels of the active ingredients in your system, making the birth control pills less effective.

What you can do

Before starting Dilantin treatment, tell your doctor if you take birth control pills. They may recommend switching to a different birth control option, such as a nonhormonal birth control.

If you have questions about taking Dilantin with birth control pills, talk with your doctor or pharmacist.

Dilantin may have other interactions. They could occur with supplements, foods, vaccines, or even lab tests. See below for details. Note that the information below does not include all other possible interactions with Dilantin.

Does Dilantin interact with supplements?

Before you start taking Dilantin, talk with your doctor and pharmacist about any herbs or vitamins and supplements you take. Sharing this information with them may help you avoid possible interactions.

Dilantin may interact with sodium bicarbonate (baking soda) supplements. Some people use these supplements as an antacid for treating conditions such as heartburn and indigestion (upset stomach).

Dilantin may be less effective if taken with sodium bicarbonate. These supplements may prevent your body from absorbing Dilantin, leading to low levels of the drug in your system. This could prevent the drug from working as well as it should.

Dilantin may also interact with caffeine supplements, which are often taken to help people stay awake. Taking Dilantin with caffeine supplements could make the supplements less effective.

Your doctor or pharmacist can recommend safe alternatives to sodium bicarbonate and caffeine supplements.

Dilantin interactions with herbs

Dilantin may interact with St. John’s wort, which is often used to ease symptoms of depression and other health conditions.

Taking Dilantin with St. John’s wort could lead to a low level of Dilantin in your system, which could make the drug less effective.

Before you start Dilantin treatment, tell your doctor if you take St. John’s wort. They may suggest alternatives to the supplement, or they may prescribe a drug other than Dilantin.

Dilantin interactions with vitamins and minerals

Dilantin may interact with vitamin D. Taking them together could make vitamin D less effective. Your doctor may adjust your dosage of vitamin D during your Dilantin treatment.

In addition, Dilantin may interact with folic acid. Taking Dilantin with this vitamin could increase your risk of seizures or make Dilantin less effective. If you take them together, your doctor may adjust your dosage of folic acid or Dilantin.

Dilantin may also interact with minerals such as calcium, magnesium, and aluminum. Taking Dilantin with these minerals can lower the level of Dilantin in your body. This could make the drug less effective.

It’s important to check with your doctor or pharmacist before taking any of these products with Dilantin.

Does Dilantin have food interactions?

Dilantin may interact with food formulas given through tube feedings. Taking Dilantin with these food formulas could make Dilantin less effective. Your doctor can recommend what to do if this interaction may affect you.

Although Dilantin may interact with sodium bicarbonate (baking soda) supplements, it’s not likely to interact with baking soda in foods. This is because foods typically contain less baking soda than a sodium bicarbonate supplement.

If you have questions about foods to avoid while taking Dilantin, talk with your doctor.

Does Dilantin interact with vaccines?

There are currently no reports of vaccines interacting with Dilantin chewable tablets, oral suspension, or extended-release oral capsules. If you have questions about getting certain vaccines during your Dilantin treatment, talk with your doctor.

Does Dilantin interact with lab tests?

Dilantin may interact with several lab tests, including certain tests for:

Before having any lab tests, be sure the person giving the test knows you’re taking Dilantin. They can tell you whether the test may be affected by Dilantin and what you should do.

Does Dilantin interact with cannabis or CBD?

Cannabis (commonly called marijuana) and cannabis products, such as cannabidiol (CBD), have been reported to interact with Dilantin.

Combining Dilantin with cannabis may raise the risk of side effects from Dilantin. The cannabis product may also be less effective.

Before you start treatment with Dilantin, tell your doctor and pharmacist if you use cannabis. By sharing this information with them, you may help prevent possible interactions.

Note: Cannabis is illegal at a federal level but is legal in many states to varying degrees.

Certain medical conditions or other health factors may raise the risk of interactions with Dilantin. Before taking Dilantin, talk with your doctor about your health history. They’ll determine whether Dilantin is right for you.

Health conditions or other factors that might interact with Dilantin include:

Diabetes or high blood sugar: Taking Dilantin may increase your blood sugar levels. If you have diabetes or high blood sugar, talk with your doctor before taking Dilantin. They can let you know whether it’s safe to take this drug.

Kidney or liver problems: If you have a kidney or liver problem (such as kidney failure or liver failure), talk with your doctor before starting Dilantin treatment.

If you have a kidney or liver condition, your body may not break down Dilantin properly. This can lead to high levels of the drug in your system, which raises your risk of side effects. Your doctor may prescribe a lower Dilantin dosage for you to reduce this risk.

Doctors are also unlikely to prescribe Dilantin for people who have had a liver problem while taking phenytoin in the past. Phenytoin is the active ingredient in Dilantin, so taking Dilantin could lead to the same liver problem.

Porphyria: Taking Dilantin may worsen a blood disorder called porphyria. If you have this condition, your doctor can help determine whether it’s safe to take Dilantin.

Pregnancy: Dilantin may not be safe to take during pregnancy. If you’re pregnant or planning a pregnancy, talk with your doctor before taking Dilantin.

If you do take Dilantin while pregnant, consider enrolling in the drug’s pregnancy registry. This registry collects details about pregnancy issues reported with Dilantin. To learn more, visit the registry website, call 888-233-2334, or talk with your doctor.

Breastfeeding: It’s not known whether it’s safe to take Dilantin while breastfeeding. The drug passes into breast milk, but it isn’t known whether the drug may cause side effects in a child who is breastfed. If you’re breastfeeding or planning to do so, talk with your doctor about your options.

Allergic reaction: If you’ve had an allergic reaction to Dilantin or any of its ingredients, your doctor will likely not prescribe Dilantin. This is because taking the drug could cause another allergic reaction. You can ask your doctor about other treatments that may be better choices for you.

Current or past depression, mood problems, or suicidal thoughts: In rare cases, taking Dilantin may lead to mood changes, such as worsening depression and suicidal thoughts or behaviors. If you’ve had depression, mood problems, or suicidal thoughts before, talk with your doctor before taking Dilantin. They can help determine whether the drug is a safe treatment option for you.

Help is out there

If you or someone you know is in crisis and considering suicide or self-harm, please seek support:

If you’re calling on behalf of someone else, stay with them until help arrives. You may remove weapons or substances that can cause harm if you can do so safely.

If you are not in the same household, stay on the phone with them until help arrives.

Was this helpful?

Taking certain steps can help you avoid interactions with Dilantin. Before starting treatment, talk with your doctor and pharmacist. Things to discuss with them include:

  • whether you drink alcohol or use cannabis
  • other medications you take, as well as any vitamins, supplements, and herbs (they can also help you fill out a medication list)
  • what to do if you start taking a new drug during your Dilantin treatment

It’s also important to understand Dilantin’s label and other paperwork that may come with the drug. Colored stickers that describe interactions may be on the label. And the paperwork (sometimes called the patient package insert or medication guide) may have other details about interactions. (If you did not get paperwork with Dilantin, ask your pharmacist to print a copy for you.)

If you have trouble reading or understanding this information, your doctor or pharmacist can help.

Taking Dilantin exactly as prescribed can also help prevent interactions.

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.