What is Phenytoin 150mg Injection?
Phenytoin 150mg injection is a prescription medicine used to control and prevent some types of seizures. And the generic name of the medicine is Phenytoin, and it belongs to the anticonvulsant/antiepileptic drug category.
It works by slowing down abnormal brain activity that causes seizures, making it an important emergency treatment in hospitals. Phenytoin 150mg injection is often used when oral tablets cannot be given, especially during status epilepticus
Status Epilepticus: When seizures (fits) occur again and again without the patient regaining consciousness, or when a seizure lasts for more than 5 minutes, it is known as Status Epilepticus.
This injection is available under several brand names, such as Dilantin, Eptoin Injection, and Fosphenytoin (a related prodrug) in some cases. Doctors usually administer it through intravenous (IV) for quick seizure control.
Composition and Strength of Phenytoin 150mg Injection
Phenytoin 150mg injection contains Phenytoin sodium as its active ingredient. It is usually formulated in a sterile solution suitable for intravenous (IV) or intramuscular (IM) administration.
- Active Ingredient: Phenytoin Sodium (equivalent to 150 mg of Phenytoin)
- Strength: 150 mg per 2 ml or 3 ml vial/ampoule (depending on the brand)
- Excipients: May include solvents and stabilizers such as propylene glycol, ethanol, and water for injection to maintain stability and solubility.
This specific 150 mg strength is preferred for emergency use, as it provides a fast therapeutic effect in controlling seizures. The injection should always be administered by healthcare professionals to avoid complications.
Uses of Phenytoin 150mg Injection
The use of Phenytoin injection is primarily used in the treatment and prevention of seizure disorders. Some of the key uses include:
- Status Epilepticus (Prolonged Seizures):
Emergency management of life-threatening continuous seizures when oral treatment is not possible. - Seizure Control During Surgery:
Used to prevent seizures in patients undergoing neurosurgery or after head trauma. - When Oral Phenytoin Cannot Be Given:
For patients who are unable to swallow tablets or capsules, the injectable form ensures continued seizure control. - Tonic-Clonic and Partial Seizures:
Helps in controlling generalized tonic-clonic seizures and complex partial seizures.
Phenytoin works by stabilizing neuronal membranes and reducing abnormal electrical activity in the brain, which makes it a cornerstone in the emergency management of epilepsy.
How Phenytoin 150mg injection Works
Phenytoin 150mg injection works by stabilizing the electrical activity in the brain.“It blocks the voltage-gated sodium channels in the brain’s neurons, which stops the rapid and uncontrolled firing of nerve signals. By doing this, it reduces the abnormal brain activity that causes seizures (fits).”
This mechanism helps in:
- Controlling seizure spread within the brain
- Reducing hyper-excitability of neurons
- Protecting brain tissue from prolonged abnormal activity during seizures
Because of its rapid action, phenytoin injection is especially important in emergencies such as status epilepticus where immediate seizure control is needed.
Dosage and Administration
The dosage of Phenytoin 150mg injection varies depending on the patient’s age, medical condition, and severity of seizures. It must always be given under medical supervision.
- Route of Administration: Intravenous (IV) injection is preferred. Intramuscular (IM) injection may be used but is less common due to slow absorption.
- Typical Adult Dose:
Loading dose: Based on the patient’s body weight, 15–20 mg per kg is given intravenously (IV), and it should be administered slowly to avoid heart-related side effects.
Maintenance dose: The further dose is adjusted so that the phenytoin level in the blood remains between 10–20 mcg/mL.
- Pediatric Use: Dosing is based on body weight and must be carefully monitored.
- Rate of Administration: Should not exceed 50 mg per minute in adults (slower in children) to prevent cardiovascular complications.
Important: Self-administration is not recommended. It must only be given in a hospital setting by trained healthcare professionals.
Side Effects of Phenytoin 150mg Injection
Like all medicines, Phenytoin 150mg injection can cause side effects. Some are mild, while others may require medical attention.
Common Side Effects:
Serious Side Effects (Require Immediate Medical Help):
- Irregular heartbeat or low blood pressure during IV infusion
- Severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis)
- Liver problems (yellowing of skin or eyes, dark urine)
- Blood disorders (low white blood cells or platelets)
- Allergic reactions (swelling, difficulty breathing)
Regular monitoring of blood phenytoin levels, liver function, and cardiac status is essential to minimize risks.
Precautions and Warnings
Before using phenytoin injection 150 mg, certain precautions must be considered to ensure safety and effectiveness:
- Medical Supervision Only:
This injection should only be given in hospitals or clinics under a doctor’s supervision due to risks of heart and respiratory complications. - Heart Conditions:
Patients who have heart disease, low blood pressure, or arrhythmia (irregular heartbeat) should take phenytoin very carefully. If the IV injection is given too quickly, these conditions can become more serious. - Liver and Kidney Impairment:
Phenytoin is metabolized in the liver. Therefore, patients with weak liver or kidney function need dose adjustments and require close monitoring.
- Pregnancy and Breastfeeding:
- May cause harm to the unborn baby (teratogenic effects). Should only be used if the potential benefit outweighs the risk.
- It passes into breast milk, so breastfeeding mothers should consult their doctor.
- May cause harm to the unborn baby (teratogenic effects). Should only be used if the potential benefit outweighs the risk.
- Alcohol Use:
Drinking alcohol can affect phenytoin levels in the blood, making seizures more difficult to control. - Allergic Reactions:
Patients with a history of hypersensitivity to phenytoin or related drugs should avoid its use.
Drug Interactions with Phenytoin Injection
Phenytoin interacts with many medicines because it induces liver enzymes (CYP450 system), which can increase or decrease the effect of other drugs.
Common Drug Interactions Include:
- Antibiotics & Antifungals: Rifampicin, isoniazid, chloramphenicol, fluconazole may alter phenytoin levels.
- Other Antiepileptics: Carbamazepine, valproic acid, phenobarbital may interact and require dose adjustment.
- Blood Thinners: Warfarin effectiveness may decrease, raising the risk of clotting.
- Contraceptives: Phenytoin reduces the effectiveness of birth control pills, leading to risk of unintended pregnancy.
- Corticosteroids: May reduce their effectiveness.
- Alcohol: Can either increase or decrease phenytoin blood levels, affecting seizure control.
Because of these interactions, regular blood tests and dose adjustments are essential for patients on long-term phenytoin therapy.
Storage and Handling Instructions
- Store Phenytoin 150mg injection at room temperature (20–25°C), away from direct light and heat.
- Do not freeze the injection.
- Keep the vial/ampoule in its original packaging until use.
- Once opened, use immediately and discard any unused portion.
- Always keep out of reach of children.
Phenytoin Injection: Price and Availability
Phenytoin 150mg injection is available in hospitals, medical stores, and online pharmacies. The price may vary depending on the brand and manufacturer, usually ranging from ₹50 to ₹150 per vial in India. It is mostly sold under brand names like Dilantin Injection and Eptoin Injection.
Frequently Asked Questions (FAQ)
What is the use of Phenytoin 150mg injection?
Phenytoin is mainly used to control seizures, especially during emergencies like status epilepticus, or when oral phenytoin cannot be given.
Can phenytoin injection cause side effects?
Yes, common side effects include dizziness, nausea, rash, and gum overgrowth. Serious reactions like irregular heartbeat or severe skin allergies may also occur.
Is phenytoin injection safe in pregnancy?
Phenytoin may pose risks during pregnancy. It should only be used if the doctor considers it absolutely necessary.
Can phenytoin interact with other medicines?
Yes, it interacts with antibiotics, antifungals, contraceptives, and blood thinners. Always inform your doctor about other medicines you are taking.
Do I need a prescription to buy Phenytoin 150mg injection?
Yes, it is a prescription-only medicine and should not be used without medical advice.
Conclusion
Phenytoin 150mg injection is a life-saving medicine widely used for the emergency management of seizures, particularly status epilepticus. As an effective anticonvulsant, it works by stabilizing abnormal brain activity and providing quick seizure control.