- What is Dilantin?
- Why is Dilantin prescribed to patients?
- Do I need a prescription for Dilantin?
- Is Dilantin available as a generic drug?
- What are the side effects of Dilantin?
- What is the dosage for Dilantin?
- Which drugs or supplements interact with Dilantin?
- Is Dilantin safe to use during pregnancy or while breastfeeding?
- What else should I know about Dilantin?
What is Dilantin?
Phenytoin is an oral and injectable anti-seizure medication first synthesized in 1908.
Why is Dilantin prescribed to patients?
Phenytoin is an anti-seizure medication (anticonvulsant) used for preventing or treating generalized tonic-clonic (grand mal) seizures, complex partial seizures (psychomotor seizures), and seizures occurring during or after neurosurgery. It may be used alone or with phenobarbital or other anticonvulsants.
What are the side effects of Dilantin?
Many adverse effects can occur during phenytoin therapy including:
- difficulty focusing (vision),
- unsteady gate,
- abnormal involuntary movements,
- abdominal pain, and
- loss of appetite.
Children and young adults can develop overgrowth of the gums during long-term therapy which requires regular treatment by a dentist. Good oral hygiene and gum massage may reduce the risk. R
ashes can occur in between 1 in 20 and 1 in 10 persons; some may be severe. Additionally, darkening coloration of the skin may develop (more commonly in women). Phenytoin can produce unusual growth of hair in some patients. This reaction most commonly affects the arms and legs but can also affect the trunk and face; it may be irreversible.
Phenytoin can potentially injure the liver although this is an uncommon occurrence.
Phenytoin can cause the platelet or white blood cell counts to drop, increasing the risk of bleeding or infection, respectively. Phenytoin also can cause anemia.
Other important side effects caused by phenytoin include sexual dysfunction, such as:
Antiepileptic medications have been associated with an increased risk of suicidal thinking and behavior. Anyone considering the use of antiepileptic drugs must balance this risk of suicide with the clinical need for the antiepileptic drug. Patients who begin antiepileptic therapy should be closely observed for clinical worsening, suicidal thoughts or unusual changes in behavior.
What is the dosage for Dilantin?
The dosing of phenytoin is patient specific. It may be given once, twice, 3, or 4 times daily. Doses are often adjusted to find the optimal dose based on measurement of blood levels. Taking phenytoin with food may reduce some of the side effects. Elderly patients, debilitated persons, and patients with certain kidney or liver diseases may need lower doses. The suspension should not be given at the same time as tube feedings since tube feedings bind to phenytoin and reduce its absorption. The recommended adult dose is 100 mg two to four times daily. Some patients may require 200 mg three times daily. Patients stabilized on 100 mg three times daily may receive 300 mg once daily of the extended release capsules.
Which drugs or supplements interact with Dilantin?
There are many potential drug interactions with phenytoin. Phenytoin can increase the metabolism (elimination) of many drugs, reducing their concentrations in the body. Drugs that may be affected include:
- digoxin (Lanoxin),
- carbamazepine (Tegretol, Tegretol XR, Equetro, Carbatrol),
- clonazepam (Klonopin),
- corticosteroids (for example, prednisone),
- oral contraceptives,
- paroxetine (Paxil, Paxil CR, Pexeva),
- tacrolimus (Prograf),
- valproic acid (Depakote, Depakote ER, Depakene, Depacon, Stavzor), and
- warfarin (Coumadin).
Phenytoin can interact with these drugs not only when it is added to therapy but also when it is discontinued. In the latter case, the concentration of the other drugs may increase. Sometimes the effect may be unpredictable. Phenytoin's metabolism may be affected by other drugs. Drugs that increase phenytoin blood levels and toxicity include:
- acute alcohol intake,
- amiodarone (Coradone),
- cimetidine (Tagamet),
- diazepam (Valium, Diastat),
- fluoxetine (Prozac),
- fluvoxamine (Luvox),
- methylphenidate (Concerta),
- omeprazole (Prilosec),
- sertraline (Zoloft),
- tolbutamide, and
- trazodone (Desyrel).
The oral absorption of phenytoin can be reduced by any of the following:
- antacids containing magnesium,
- calcium carbonate, or aluminum;
- calcium salts; or enteral feeding products (tube feedings).
Separating the administration of phenytoin and enteral feeding products, antacids, or calcium salts by at least 2 hours will help avoid this interaction.
Is Dilantin safe to use during pregnancy or while breastfeeding?
There is an increased risk of malformations and birth defects in women taking phenytoin. Thus, phenytoin should be used in pregnancy only if the physician feels that the potential benefit outweighs the risk.
Phenytoin is secreted into breast milk. Breastfeeding is not recommended for persons taking phenytoin.
What else should I know about Dilantin?
What preparations of Dilantin are available?
Capsules (extended or immediate release): 30, 100, 200, and 300 mg; Chewable Tablet: 50 mg; Suspension: 125 mg/5 mL; Injection: 50 mg/mL.
How should I keep Dilantin stored?
Capsules, tablets, and suspension should be kept at room temperature, 68 F - 77 F (20 C - 25 C).
How does Dilantin work?
The exact mechanism of action is not known, Phenytoin may work by reducing the sensitivity of nerves in the brain to excessive stimulation and reducing transmission of impulses between nerves.
When was Dilantin approved by the FDA?
Phenytoin was originally approved by the FDA in 1939.
Multimedia: Slideshows, Images & Quizzes
Epilepsy & Seizures Quiz: What Causes Seizures?
Do you know the difference between seizures and epilepsy? What are the types of seizures? Take the Epilepsy & Seizures Quiz to...
Systemic Lupus Erythematosus Quiz: Test Your SLE IQ
This Lupus Quiz covers causes, signs, symptoms, facts, and treatments for this inflammatory autoimmune disease....
Picture of Gingival Hyperplasia from Phenytoin
The mechanisms of adverse reactions to drugs vary. Some, like the urticarial or eczematous, are clearly based on an allergic or...
Related Disease Conditions
Cushing's syndrome, sometimes referred to as hypercortisolism, is a hormonal disorder caused by prolonged exposure to high levels...
Peripheral Neuropathy (Causes, Symptoms, Treatment Medications)
Peripheral neuropathy is a problem with the functioning of the nerves outside of the spinal cord. Symptoms may include numbness,...
Learn about osteoporosis, a condition characterized by the loss of bone density, which leads to an increased risk of bone...
Epilepsy is a brain disorder in which the person has seizures. There are two kinds of seizures, focal and generalized. There are...
Lupus (Systemic Lupus Erythematosus or SLE)
Systemic lupus erythematosus is a condition characterized by chronic inflammation of body tissues caused by autoimmune disease....
Fabry Disease (Symptoms and Life Expectancy)
Fabry disease (Fabry's disease, alpha-galactosidase-A) is a genetic disorder with symptoms such as burning sensations in...
Peyronie's Disease (Curvature of the Penis)
Peyronie's disease or curvature of the penis (Peyronie disease) is a condition in which scar tissue develops inside the penis....
Pain that originates in the face is referred to as trigeminal neuralgia. This pain may be caused by: an injury, an infection...
Preeclampsia and Eclampsia
Preeclampsia is a condition in pregnant women marked by high blood pressure and a high level of protein in the urine. Eclampsia...
Seizures Symptoms and Types
Seizures are divided into two categories: generalized and partial. Generalized seizures are produced by electrical impulses from...
Fragile X Syndrome
Fragile X syndrome is the most common inherited form of mental retardation. It's caused by a mutation on the X chromosome. People...
Cysticercosis (Pork Tapeworm Infection)
Cysticercosis is an infection caused by Taenia solium, the pork tapeworm. Symptoms include seizures, lethargy, nausea and...
Treatment & Diagnosis
- Epilepsy and Seizures FAQs
- Systemic Lupus Erythematosus FAQs
- Drugs: The Most Common Medication Errors
- How To Reduce Your Medication Costs
- Pharmacy Visit, How To Get The Most Out of Your Visit
- Indications for Drugs: Approved vs. Non-approved
- Drugs: Buying Prescription Drugs Online Safely
- Medication Disposal
- Dangers of Mixing Medications
- Herbs: Toxicities and Drug Interactions
- Generic Drugs, Are They as Good as Brand-Names?
Medications & Supplements
Prevention & Wellness
Subscribe to MedicineNet's General Health Newsletter
Health Solutions From Our Sponsors
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
FDA Prescribing Information