Hidantal

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Hidantal

Method of action: Antiepileptic

Treatment option:

Medically reviewed

Marina Burgos

Last updated on 10/01/2026

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Hidantal

Property Description
Active ingredient Phenytoin (Diphenylhydantoin)
Forms Tablets, capsules, oral suspension, parenteral solution
Pharmacological class Anticonvulsant, Antiepileptic Drug (AED)
General purpose Management of seizure disorders
Origin Synthetic compound (Hydantoin derivative)

What Type of Medicine is Hidantal? (Identity and Classification)

Hidantal is a trade name for a medication whose active component is the substance Phenytoin, also known chemically as Diphenylhydantoin. It is primarily classified as an antiepileptic drug (AED), placing it within the broader pharmacological category of anticonvulsants. Phenytoin is considered an essential medicine, underscoring its established importance in seizure management globally.

The active substance is chemically categorized as a hydantoin derivative, confirming its status as a foundational, synthetic compound. This compound's efficacy has been clinically recognized through decades of pharmacological studies for its role in controlling electrical activity in the brain.

Composition, Origin, and Forms

The medicine is supplied as a single active ingredient product, consisting solely of Phenytoin combined with a suitable pharmaceutical base. To ensure flexibility in patient care, the medication is available in several dosage forms, including solid oral preparations like tablets and capsules, an oral suspension for easier consumption, and a specialized parenteral solution for injection.

These varied preparations define the possible routes of administration, which are typically oral for chronic, ongoing management and intravenous for urgent medical needs. The liquid oral suspension form is often used for patients, such as children, who may have difficulty swallowing solid forms.

General Purpose: Stabilizing Neuronal Activity

The core general purpose of the medication is to control and suppress the abnormal electrical activity in the brain that characterizes various seizure disorders and epilepsy. This effect is achieved through the stabilization of neuronal activity, which helps limit the capacity of nerve cells to generate rapid, uncontrolled electrical discharges. This action provides the necessary regulation to prevent the onset and widespread propagation of seizures, forming a typical scenario for its use in patients diagnosed with tonic-clonic or complex partial seizures.

What side effects are possible with Hidantal?

Possible Side Effects and Safety Information

The safety profile for Hidantal is defined by its potential for both concentration-dependent toxicity and rare, but serious, idiosyncratic adverse reactions.

Documented Adverse Reactions

Adverse effects are categorized by frequency, as documented in official regulatory sources:

Classification Examples of Reactions
Very Common Nystagmus (involuntary eye movement), ataxia (lack of muscle coordination), dizziness, headache, confusion, nausea, vomiting, hirsutism, and gingival hyperplasia (gum enlargement). These are often dose-related.
Common Tremor, peripheral neuropathy, and megaloblastic anemia.
Uncommon to Rare Severe skin reactions, blood disorders, and liver injury.

Serious and Clinically Significant Safety Concerns

Official documents highlight the risk of several serious, potentially life-threatening adverse reactions that are not related to dose:

  • Severe Skin and Systemic Reactions: These include Stevens-Johnson Syndrome (SJS), Toxic Epidermal Necrolysis (TEN), and Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS). These reactions require immediate attention.
  • Blood and Lymphatic Disorders: Rare, serious blood dyscrasias such as agranulocytosis and aplastic anemia are documented.
  • Hepatotoxicity: Rare cases of toxic hepatitis, including fatal outcomes, have been reported.
  • Cardiovascular Risk: Rapid intravenous administration is contraindicated due to the risk of severe hypotension and cardiac arrhythmias (such as ventricular fibrillation).

Population-Specific Considerations

  • Pregnancy: Use during pregnancy is associated with teratogenic risks, including fetal hydantoin syndrome, necessitating specific regulatory warnings.
  • Genetic Risk: Individuals with the HLA-B*1502 allele may have an increased risk of SJS/TEN and require particular caution.

Overdose and Emergency Response

Overdose and When to Seek Help

Phenytoin, the active substance in Hidantal, overdose presents a spectrum of documented signs, primarily affecting the Central Nervous System (CNS). Initial manifestations are often dose-dependent and include nystagmus (uncontrolled eye movement), ataxia (poor coordination), slurred speech, somnolence, and mental confusion. In severe overdose cases, these symptoms may progress to stupor and coma.

The official regulatory profile emphasizes the risk of life-threatening outcomes, including severe cardiovascular events. These may involve severe hypotension (low blood pressure) and various cardiac arrhythmias, which can lead to respiratory depression or cardiac arrest. This risk is particularly noted following rapid intravenous exposure.

Immediate medical attention is required when any overdose is suspected. Government guidance strictly mandates that individuals call a Poison Control Center or emergency room right away. Since no specific antidote is known, clinical management involves strictly symptomatic and supportive care, including continuous monitoring of the electrocardiogram (ECG) and blood pressure, as stated in official labeling. Special consideration is given to critically ill and elderly patients, who are documented to be at higher risk for severe cardiovascular complications.

Therapeutic Uses of Hidantal

What Hidantal Treats: Main Uses and Benefits

The medication is commonly used to help manage symptoms related to specific seizure types, which are conditions characterized by periods of heightened neurological activity. Its uses generally address tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures.

Hidantal is relevant for easing symptom clusters that may become intense or disruptive, such as uncontrolled muscle contractions and motor fluctuations. This support helps address symptoms of increased neurological activity that interfere with daily functioning and contributes to easing the overall symptom load. It is applied in clinical settings that involve acute or unstable symptom patterns, assisting with maintaining functional stability when symptoms become temporarily overwhelming.


Key Therapeutic Domains

The medication is utilized across domains where short-term symptomatic assistance is needed, including supporting functional stability during acute episodes, managing symptoms of heightened neurological activity, and providing supportive relief in high-stress clinical contexts. It provides supportive relief when symptoms related to organ-specific functional stress appear suddenly.

“The support provided may help offer symptomatic relief that helps patients cope more steadily during difficult episodes.”


Quick Fact: Support for Motor Fluctuations

Hidantal plays a role in managing symptoms of increased neurological or muscular activity, which contributes to maintaining a sense of stability when these symptoms become more noticeable.

Eligibility and Restrictions for Use

Hidantal (phenytoin) is generally prescribed for the control of certain types of seizures, including generalized tonic-clonic and complex partial seizures, and for the prevention and treatment of seizures occurring during or following neurosurgery. It may be used in adults and children, with dosing carefully individualized based on age, weight, and serum drug levels.


Contraindications (Who Should Not Use Hidantal)

Individuals should not use Hidantal if they have a history of hypersensitivity or allergic reaction to phenytoin, any of its inactive ingredients, or other medications in the hydantoin class (such as ethotoin or fosphenytoin). Additionally, due to the risk of serious cardiac effects, it is contraindicated in patients with certain heart rhythm problems, including sinus bradycardia, sinoatrial block, second- and third-degree atrioventricular (AV) block, or Adams-Stokes syndrome.


Warnings and Precautions

Caution is advised for patients with certain medical conditions, as the drug may worsen them or require dose adjustment. This includes liver disease, kidney disease, diabetes, porphyria, or hypoalbuminemia (low blood albumin). Pregnant women should not start taking this medication unless the benefit clearly outweighs the risk, as phenytoin can be harmful to the fetus, causing fetal hydantoin syndrome. Patients should also be aware of the potential for severe skin reactions, which can occur weeks to months after starting the drug.

What should I know about interactions with other medicines?

Hidantal (Phenytoin) is primarily involved in pharmacokinetic interactions, a classification defined by its regulatory profile. The drug is metabolized by the CYP2C9 and CYP2C19 enzymes, making its concentration susceptible to co-administered medicines that inhibit these pathways (e.g., Amiodarone, Fluoxetine, Azole antifungals), which can increase Phenytoin plasma levels. Conversely, Phenytoin is officially documented as an inducer of hepatic metabolizing enzymes, which may accelerate the clearance and reduce the exposure of numerous co-administered drugs that are substrates of the CYP system.

The regulatory label includes strict restrictions: Co-administration with the antiviral medicine Delavirdine is contraindicated due to the potential for loss of virologic response. Furthermore, it is suggested that Phenytoin not be administered concomitantly with enteral feeding preparations and related nutritional supplements, as this is associated with lower-than-expected Phenytoin serum levels. Acute alcoholic intake is documented to potentially increase levels, while chronic alcohol use may decrease levels.

For specific populations, official regulatory guidance states that patients with hepatic or renal impairment or hypoalbuminemia have an increased fraction of unbound Phenytoin. This requires that monitoring should account for this specific clearance consideration.

Mechanism of Action

The pharmacological mechanism of Hidantal, or Phenytoin, centers on the use-dependent blockade of voltage-gated sodium channels ( Na^+) found within neuronal membranes. This interaction is selective; the drug binds preferentially to the channel when it is in its inactive state, a condition reached during and immediately following high-frequency cellular firing. By stabilizing the Na^+ channel in this non-conducting state, Phenytoin effectively prolongs the refractory period. This action critically restricts the necessary inward flow of sodium ions, thereby inhibiting the nerve cell's intrinsic capacity to generate sustained high-frequency repetitive firing (SHFRF). The resulting neuronal membrane hyperpolarization and inhibition of electrical signal spread throughout the central nervous system (CNS) constitutes the direct physiological effect of the mechanism. However, this action is constrained, as the drug does not modulate T-type calcium channels, limiting its effect to primarily Na^+-dependent neuronal conductance pathways.

Dosage and Administration Information

How to Use Hidantal (Phenytoin) — Official Administration Guidelines

Hidantal (phenytoin) is for oral administration and must be used exactly as prescribed by a physician. The official instructions emphasize that dosage is highly individualized and requires close medical monitoring.


Dosage and Timing

Administration Element Official Instruction
Route and Dosing Oral administration; doses are typically divided into one to three daily doses. Initial adult doses are often 100 mg three times a day (t.i.d.).
Timing with Meals The medicine should be taken with or immediately after meals.
Frequency Adjustment Dose adjustments, whether increasing or decreasing, should not be made more frequently than every 7 to 10 days as steady-state blood levels require time to achieve.

Administration Rules

  • Preparation: If using the oral suspension (liquid form), the bottle must be shaken well before each use to ensure the medication is evenly mixed. Use a calibrated measuring device, not a household spoon, to ensure accuracy.
  • Missed Dose: If a dose is missed, take it as soon as possible, unless it is almost time for the next scheduled dose. Do not double the dose to make up for the missed one.
  • Discontinuation: The medicine must not be stopped abruptly. Discontinuation or dose reduction must be done gradually and only under the supervision of a physician, as sudden cessation can lead to serious problems.
  • Age-Specific: Dosing for children is typically calculated based on body weight (mg/kg/day). Elderly patients often require a lower initial dose and slower titration due to altered drug clearance.

Recent Clinical Evidence

Research Evidence / Overview of Studies for Hidantal

Evidence for Use in Generalized Tonic-Clonic Seizures

The evidence base for Hidantal in the context of generalized tonic-clonic seizures is largely drawn from Randomized Controlled Trials (RCTs) and systematic reviews. These studies examined how symptoms evolved in observed populations, focusing on time-based outcomes like the duration until a seizure relapse occurred and the proportion of patients who achieved a seizure-free period for a significant duration. The studies included adults and older children newly or recently diagnosed with this specific seizure type. The findings describe patterns observed when Phenytoin was compared to other established antiepileptic drugs, with some trials noting results that were not notably different for the outcomes examined. Comparative evidence is lacking with some of the newer medications used today.

Evidence for Use in Complex Partial Seizures

Hidantal was studied for complex partial seizures (sometimes called focal seizures) through RCTs and other systematic reviews. Research explored outcomes related to episodic or acute changes in seizure frequency. Studies monitored for changes measured during the study period, tracking how the time until a seizure recurred was measured. A known research limitation is that the populations included in the initial regulatory trials were often highly selected. This means the results apply only to the populations studied, and the evidence provides limited context for the use of the drug in patients not included in the original trials.

Research Gaps and Uncertainty

Research has explored the possibility of sustained seizure control over the long term, but long-term effects are not fully established for all aspects of treatment. Data for certain groups, such as pediatric patients, remains insufficient. A major limitation across the evidence base is that the design of many initial trials was for a short duration, and their sample sizes were small when breaking down results into different seizure types. Therefore, comparative evidence is lacking for many direct, high-quality head-to-head assessments against newer antiepileptic drugs.

Frequently Asked Questions (FAQ)

Common questions about Hidantal (FAQ)

Q: What is Hidantal (Phenytoin) and what is it used for?

A: Hidantal is a brand name for the medication phenytoin, which is an antiepileptic drug (also known as an anticonvulsant).

It is primarily used to control and prevent seizures (convulsions) in patients with epilepsy. It can also be used to prevent seizures that may occur during or after neurosurgery.

Q: How does Hidantal work?

A: Hidantal works by stabilizing electrical activity in the brain. It limits the spread of seizure activity by slowing down the movement of sodium ions across nerve cell membranes.

This action makes nerve cells less excitable, which helps to reduce the frequency and severity of seizures.

Q: How should I take Hidantal?

A: Always take Hidantal exactly as your doctor prescribes. The dose is personalized based on your medical condition and response to treatment. Do not change your dose without consulting your doctor.

  • Swallow the capsules or tablets whole with a full glass of water.
  • Try to take the medication at the same time each day to maintain a consistent level in your bloodstream.
  • If you are taking an extended-release form, do not crush or chew it.
  • If you miss a dose, take it as soon as you remember, unless it is almost time for your next scheduled dose. Do not double your dose to make up for the missed one.

Q: Can I drink alcohol while taking Hidantal?

A: You should generally avoid or severely limit alcohol consumption while taking Hidantal. Alcohol can:

  • Increase the risk of central nervous system side effects like drowsiness, dizziness, and coordination problems.
  • Potentially interfere with the drug’s effectiveness in controlling seizures.
  • In some cases, chronic alcohol use can change how your body processes the medication, leading to unpredictable drug levels.

Discuss your alcohol use with your prescribing healthcare provider.

Q: What are some common side effects of Hidantal?

A: Common side effects often involve the central nervous system and can include:

  • Dizziness or lightheadedness
  • Drowsiness
  • Difficulty with coordination (ataxia)
  • Slurred speech
  • Confusion

Other common side effects include:

  • Gingival hyperplasia (swollen or overgrown gums)
  • Mild stomach upset or nausea
  • Unusual eye movements (nystagmus)

Report any concerning or persistent side effects to your healthcare provider.

How should Hidantal be stored and disposed of?

The storage and disposal of Hidantal (phenytoin) must strictly adhere to the conditions outlined in regulatory labeling to maintain stability and safety.

Storage Requirements

Dosage Form Condition Constraint
Oral Forms Store at controlled room temperature (20 C to 25 C) and protect from moisture and light. Do not freeze the oral suspension.
IV Solution Administer diluted solution immediately after preparation. Do not refrigerate the prepared infusion.

All forms must be stored in a tight container and kept out of the reach of children. Unused contents of single-dose injectable containers must be discarded. Expired or unused oral product should be disposed of in accordance with local regulations or a community drug take-back program. Disposal must avoid environmental contamination.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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