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Dilantin (Generic Phenytoin Injection)

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Phenytoin injection, used primarily to manage and prevent seizures, carries several risks and potential side effects:

  • Cardiovascular Risks: There can be serious cardiovascular side effects such as hypotension (low blood pressure) and arrhythmias (abnormal heart rhythms), particularly when administered too rapidly.
  • Central Nervous System Effects: Patients might experience dizziness, drowsiness, nystagmus (involuntary eye movement), and ataxia (loss of coordination).
  • Dermatologic Reactions: There is a risk of severe skin reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis, which are life-threatening conditions.
  • Hypersensitivity Reactions: Allergic reactions such as fever, rash, and lymphadenopathy (swollen lymph nodes) can occur.
  • Hematologic Issues: Blood disorders like leukopenia (low white blood cell count), thrombocytopenia (low platelet count), and agranulocytosis (severe low white blood cell count) are possible.
  • Liver Toxicity: Liver damage, including hepatic necrosis and hepatitis, can occur, which necessitates regular monitoring of liver function.
  • Gingival Hyperplasia: Chronic use can lead to overgrowth of the gums.

Due to these potential risks, phenytoin injection should be administered under medical supervision, with careful monitoring for adverse reactions.

Why is this medication prescribed?

Phenytoin injection is primarily prescribed for:

  • Seizure Control: Phenytoin injection is used to manage and prevent various types of seizures, particularly tonic-clonic (grand mal) and complex partial seizures.
  • Status Epilepticus: It is often administered in emergency situations to control status epilepticus, a prolonged or repeated seizure condition that is a medical emergency.
  • Prophylaxis: It can be used to prevent seizures following neurosurgery or head trauma.

How should this medicine be used?

When using phenytoin, it’s essential to follow your doctor’s instructions carefully. Here are some general guidelines for its use:

  • Administration: Phenytoin injection is typically administered intravenously. The injection should be given by a healthcare professional in a clinical setting to ensure proper monitoring and immediate management of potential side effects.
  • Dosage: The dosage is individualized based on the patient’s condition, age, weight, and response to the medication. For status epilepticus, the initial dose is generally administered as a rapid infusion, followed by maintenance doses if needed. For maintenance therapy, it may be administered in divided doses.
  • Preparation: Phenytoin injection must be diluted with a compatible IV fluid before administration. It is usually diluted in normal saline and must be administered slowly to avoid complications such as cardiovascular issues.
  • Monitoring: During administration, patients should be closely monitored for signs of toxicity, cardiovascular reactions, and other side effects. Blood levels of phenytoin may be periodically checked to ensure they are within the therapeutic range and to adjust the dose accordingly.
  • Precautions: It is important to avoid rapid administration as this can lead to severe hypotension and cardiac arrhythmias. Proper aseptic technique should be used to prevent infections.
  • Interactions: Phenytoin can interact with many other medications, so it’s essential to inform healthcare providers about all other drugs the patient is taking to avoid adverse interactions.

Always follow the specific instructions provided by the healthcare provider and the guidelines given with the medication for safe and effective use.

Other uses for Ergoloid Mesylates

  • Prophylaxis for Seizures: It can be used as a preventive measure in patients at risk of seizures, especially after neurosurgery or severe head trauma.
  • Neuropathic Pain: Though less common, phenytoin has been used off-label for treating certain types of neuropathic pain.

What special precautions should I follow?

Special Precautions to Follow for Phenytoin Injection:

  • Allergies: Inform your healthcare provider if you have a history of allergies to phenytoin or any other medications, especially similar anticonvulsants.
  • Medical History: Share your complete medical history, particularly if you have conditions like heart disease, liver disease, diabetes, porphyria, or bone marrow suppression.
  • Medication Interactions: Phenytoin interacts with many medications, including warfarin, oral contraceptives, and other antiepileptic drugs. Always inform your doctor about all medications and supplements you are taking.
  • Pregnancy and Breastfeeding: Phenytoin can harm an unborn baby and may cause birth defects. Inform your doctor if you are pregnant, planning to become pregnant, or breastfeeding.
  • Proper Administration: Phenytoin should be administered slowly and not exceed the recommended infusion rate to prevent severe cardiovascular reactions. Ensure it is diluted properly with a compatible IV fluid like normal saline.
  • Monitoring: Continuous monitoring of heart function, blood pressure, and respiratory status is crucial during administration. Regular blood tests to monitor phenytoin levels and liver function tests are also important.
  • Side Effects: Be aware of possible side effects, such as dizziness, drowsiness, unsteadiness, nausea, vomiting, or gingival hyperplasia (overgrowth of gum tissue). Report any severe or unusual side effects to your healthcare provider immediately.
  • Avoid Alcohol: Alcohol can increase the risk of side effects and decrease the effectiveness of phenytoin.
  • Driving and Operating Machinery: Due to potential side effects like dizziness and drowsiness, be cautious when driving or operating heavy machinery.
  • Dental Hygiene: Maintain good dental hygiene and regular dental check-ups, as phenytoin can cause gum overgrowth.
  • Missed Doses: If you miss a dose, follow the instructions given by your healthcare provider. Do not double up on doses to make up for a missed one.
  • Storage and Handling: Ensure phenytoin injection is stored as per the manufacturer’s instructions and handled properly to maintain its efficacy and safety.

By following these precautions, you can help ensure the safe and effective use of phenytoin injection. Always adhere to the advice and instructions provided by your healthcare provider.

What special dietary instructions should I follow?

  • Consistency in Diet: Maintain a consistent diet, as changes in nutrition can affect phenytoin levels in the blood.
  • Vitamin D and Calcium: Phenytoin can affect bone density, so ensure adequate intake of vitamin D and calcium.
  • Folic Acid: Phenytoin can lower folic acid levels; consider discussing with your doctor whether you need to take folic acid supplements.

What should I do if I forget a dose?

  • Immediate Action: If you miss a dose of phenytoin, take it as soon as you remember. If it is close to the time for your next dose, skip the missed dose and proceed with your regular dosing schedule.
  • Do Not Double Dose: Do not take two doses at the same time to make up for a missed dose. Taking too much phenytoin can lead to serious side effects.
  • Consult Your Doctor: If you are unsure about what to do after missing a dose, contact your healthcare provider for guidance.

What side effects can this medication cause?

Phenytoin injection, like any medication, can potentially cause side effects. Common side effects may include:

  • Dizziness or drowsiness: Phenytoin can affect the central nervous system, leading to dizziness or drowsiness in some individuals.
  • Nausea or vomiting: Gastrointestinal upset is a common side effect of many medications, including phenytoin.
  • Gingival hyperplasia: This refers to an overgrowth of gum tissue, which can occur with long-term use of phenytoin.
  • Injection site reactions: Pain, redness, or irritation at the injection site can occur.
  • Skin rash: Some individuals may experience an allergic reaction to phenytoin, resulting in a rash.
  • Hypotension: Phenytoin can cause low blood pressure in some individuals.
  • Liver toxicity: Rarely, phenytoin can affect liver function, leading to elevated liver enzymes or liver damage.
  • Blood disorders: Phenytoin can affect blood cell counts, leading to conditions such as leukopenia (low white blood cell count) or thrombocytopenia (low platelet count).
  • Osteoporosis: Long-term use of phenytoin may increase the risk of osteoporosis, particularly in older adults.
  • Megaloblastic anemia: Phenytoin can interfere with folic acid metabolism, leading to a type of anemia characterized by large, immature red blood cells.

These are not all the possible side effects of phenytoin injection, and individuals may experience other side effects not listed here. It’s essential to discuss any concerns or potential side effects with a healthcare provider.

What should I know about storage and disposal of this medication?

Storage and Disposal of Phenytoin Injection:


  • Temperature: Store phenytoin injection at room temperature, typically between 20°C to 25°C (68°F to 77°F). Do not freeze.
  • Light Sensitivity: Protect the injection from light. Keep it in its original packaging until ready for use.
  • Environment: Store in a dry place away from moisture and out of reach of children and pets.


  • Unused Medication: Do not flush phenytoin injection down the toilet or pour it into a drain. Follow local regulations for disposing of medical waste.
  • Sharps Disposal: If the injection was administered using a needle, dispose of needles and syringes in a designated sharps container. Follow local guidelines for the disposal of sharps.

In case of emergency/overdose

  • Seek Medical Assistance: In case of overdose or emergency, such as severe allergic reactions, cardiac issues, or overdose symptoms like excessive drowsiness or confusion, seek immediate medical attention by calling emergency services or going to the nearest emergency room.
  • Poison Control: You can also contact your local poison control center for guidance on what to do in case of overdose or accidental ingestion of phenytoin injection.

What other information should I know?

  • Follow-Up: Attend all scheduled appointments with your healthcare provider for monitoring of your condition and response to treatment.
  • Regular Blood Tests: Your doctor may order regular blood tests to monitor phenytoin levels and check for any adverse effects on blood cells and liver function.
  • Avoid Abrupt Discontinuation: Do not stop taking phenytoin suddenly without consulting your doctor, as it may lead to increased seizure frequency or withdrawal symptoms.
  • Medication Identification: Ensure you are familiar with the appearance of your phenytoin injection and always check the label before administration to confirm it is the correct medication and strength.
  • Medical Alert Bracelet: Consider wearing a medical alert bracelet or carrying a medical identification card indicating that you are taking phenytoin in case of emergencies.
  • Inform Healthcare Providers: Inform all healthcare providers involved in your care, including dentists and surgeons, that you are taking phenytoin, as it may interact with other medications or affect anesthesia.
  • Avoid Alcohol: Limit alcohol consumption while taking phenytoin, as it can increase the risk of side effects and reduce the effectiveness of the medication.
  • Educate Close Contacts: Educate family members or close contacts about your condition and how to respond in case of a seizure or emergency situation.

Following these guidelines can help you safely and effectively manage your treatment with phenytoin injection. Always consult your healthcare provider if you have any questions or concerns about your medication or treatment plan.

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