Common Side Effects of Dilantin (Phenytoin)

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Dilantin (phenytoin) is a prescription drug. It is an anti-epileptic drug that is also called an anticonvulsant. This medicine works by slowing down the impulses in the brain that can lead to seizures.
Dilantin, in other words, is used in controlling seizures. However, this medicine does not help in treating all types of seizures, and only your doctor who is aware of your history can let you know if this medicine is right for you. 


How It Works

Phenytoin is a part of a drug group known as antiepileptic drugs or AEDs. A drug group is a group of medication that can work similarly and are often used in treating similar medical conditions.
Phenytoin, in turn, works by not allowing the seizure activity to spread inside the brain. This medication also helps by controlling the neurons inside the brain and not allowing them to become active. When these neurons are not active, this reduces the number of seizures you have.


Side Effects

Some common side effects on Phenytoin include:
  • A headache
  • Nausea
  • Vomiting
  • Constipation
  • Dizziness
  • Drowsiness
  • Feeling of spinning
  • Trouble sleeping
  • Nervousness


If any of these effects start to get worse and become persistent, let your doctor know immediately.
Phenytoin may also lead to bleeding and swelling of gums and in cases like this, massage your gums and brush your teeth to reduce this problem and get rid of it.
Remember that your physician has advised you this medication because he or she believes that the benefits this medication has are far greater than the risk of side effects. Many people who use this drug do not experience any dangerous side effects but if you
undergo any of the following sensations, visit your doctor:
  • Unusual eye movement
  • Loss of coordination
  • Confusion
  • Slurred speech
  • Twitching of muscles
  • Blurred vision
  • Facial changes
  • Excessive growth of hair
Some people who take Phenytoin may also experience suicidal thoughts, depression, and other mental conditions. Tell your doctor instantly if you notice any change in your mental mood or behavior.
For males, it is possible that they may experience a painful and prolonged erection that might last for hours; if this occurs then stop using this drug and seek medical help.



Before using this medication, make sure that your doctor is aware of all your allergies and also aware if you are allergic to any other anti-seizure medication.
Dilantin medication may contain some inactive ingredients that can cause allergic reactions as well.
Before using this drug, let your doctor know about your medical history, especially if you have abused alcohol in the past, or had blood conditions, liver disease, diabetes, lupus, vitamin B-12 deficiency, or folate.
This medication may even make you drowsy and dizzy, so avoid alcohol and marijuana after using this drug and do not use machinery, drive, or do any activity that requires you to stay alert.
Limit the consumption of alcohol when using this drug as this may have a direct effect on your blood level.
If you have diabetes, then this drug may increase the sugar level in your blood so check it regularly, and in case of any abnormal results; let your doctor know.
With this medicine, you may need to take Vitamin D supplements as this will keep your bones strong and prevent it from weakening.
During pregnancy, use this drug if absolutely necessary as it may harm your unborn baby.
Untreated seizures can also be very dangerous and might be fatal for pregnant women and babies, so do not stop taking Dilantin unless told by your doctor otherwise.
If you are trying to conceive, talk to your doctor about the risk and benefits this drug has.
Also, birth control pill, implants, and patches may not work with this medication so do discuss dependable forms of birth control with your doctor.
Phenytoin can pass into your breast milk so make sure you talk to your doctor before you breastfeed.



Phenytoin can interact with other medications, vitamins, or herbal products. Some interactions can also increase the chances of you being more susceptible to side effects.
Some drugs that can interact with Phenytoin are listed below.

Drugs for the heart

Taking Phenytoin along with drugs for cardiovascular conditions can increase the level of phenytoin in the body and lead to more side effects. These drugs include amiodarone and ticlopidine. 

Drugs for cholesterol

Using phenytoin with fluvastatin can increase the level of both these drugs and hence can lead to greater side effects.
Anti-seizure drugs
Taking phenytoin along with anti-seizure drugs can lead to an increase in the amount of phenytoin in the body. Examples of these drugs include:
  • Ethosuximide
  • Felbamate
  • Oxcarbazepine
  • Methsuximide
  • Topiramate
Some anti-seizure drugs, when taken with phenytoin in the body, can reduce the level of phenytoin in your body which is why this drug may not be able to control seizures. These drugs that lower the functionality of phenytoin includes carbamazepine and vigabatrin.

Antifungal drugs

Taking phenytoin with antifungal drugs can increase the level of phenytoin inside your body. This can also increase side effects, and these drugs include:
  • Ketoconazole
  • Itraconazole
  • Miconazole
  • Voriconazole
  • Fluconazole

Antibiotics and cancer drugs

Taking phenytoin along with cancer drugs and antibiotics can also increase the amount of phenytoin in the body. Some examples of such drugs include chloramphenicol, capecitabine, and fluorouracil.


How to take Dilantin

Do not stop using this drug suddenly as it can lead to some very serious problems which include more seizures or seizures that can persist.
If you miss a dose, then you can increase the risk of having seizures, so it is advised that you take this medication at the same time every day; this way you’ll remember to take it.
Do not overdose on this drug as it has some very dangerous symptoms on overdosing such as tremor, slurred speech, overactive reflexes, and lack of energy, vomiting, nausea, and blurred vision. You can also end up in a coma due to increased dosage.


Common Side Effects of Diltiazem

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Diltiazem is a medication that can be used to treat hypertension and chest pain along with certain rhythm disorders.
Diltiazem is available in three forms; an immediate release capsule, extended-release capsules, and as an intravenous solution. This medication acts as a calcium channel blocker.

Read more: Common Side Effects of Diltiazem

Common Side Effects of Diovan HCT

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Hydrochlorothiazide is a thiazide water pill that can help in preventing your body from absorbing high amounts of salt. Absorbing high amounts of salt can lead to fluid retention. A water pill can help in producing more urine, and this helps in getting rid of any extra salt or water present in our body.
Valsartan or hydrochlorothiazide is a prescription drug that is known by its brand name of Diovan HCT. This drug is used in treating high blood pressure, and high blood pressure, if left untreated, can lead to heart attacks, kidney problems, and stoke.
This medication is usually given after other blood pressure medications have been tried and tested without any success.

Read more: Common Side Effects of Diovan HCT

Common Side Effects of Diphenhydramine

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Diphenhydramine belongs to the family of medication known as antihistamines. This family of drugs is used for relieving symptoms of allergies, common cold, and hay fever. When one's body comes in contact with an allergy trigger such as pollen, dust mites, ragweed, etc., chemicals called histamines are formed.

These chemicals then cause the nose tissues to swell up making it stuffy which causes your noses and eyes to run and itch. These chemicals can also cause hives as well as other skin rashes. Antihistamines are drugs used to block these histamines which then reduce the allergy symptoms.

This drug helps in relieving not only different allergies but can also be used for seasonal allergies as well as food allergies. Diphenhydramine is used for treating allergy symptoms that include rashes, itchy and watering eyes and nose, cough, etc. This medication is also used for treating dizziness, vomiting, and nausea that is caused by motion sickness. It even helps in relaxing the mind and allows you to sleep easily.

Read more: Common Side Effects of Diphenhydramine