Phenytoin is an antiepileptic medicine used to treat tonic-clonic epilepsy. In addition, this medication may also be indicated to treat and prevent seizures that begin during or after brain surgery and to treat migraines.
This medication works by decreasing excessive electrical activity in the brain and must be prescribed by a neurologist, who may recommend it in the form of 100 mg tablets, 20 mg/mL oral suspension, or 50 mL/mg intravenous injection, which must be applied in a hospital environment.
Phenytoin is obtained in pharmacies upon presentation of a medical prescription and retention of a copy of the prescription by the pharmacy, and can be found under the generic name “phenytoin sodium” or under the commercial names of Hidantal, Epelin, Fenital and Uniphenytoin, for example .
What is it for
Phenytoin is indicated for the treatment of:
- Epilepsy;
- Convulsive seizures, generalized tonic-clonic seizures or complete partial seizure;
- Preventing seizures during or after brain or nervous system surgery
In addition, phenytoin can also be indicated for trigeminal neuralgia, which is a change in a nerve in the face that causes intense pain, like a shock, when touching the face, eating or smiling. Learn more about trigeminal neuralgia.
Phenytoin can also be prescribed for the treatment of migraines, some cases of delirium and hallucinations, some changes in the heart rhythm, and in intoxication due to digitalis ingestion, these are medications that are used to treat some heart problems.
How to use
The recommended form of use and dose of phenytoin vary depending on the person’s age and the problem to be treated.
1. 100 mg Phenytoin Tablets
Phenytoin should be taken with at least half a glass of water, during or after meals.
- Adults: 1 tablet of 100 mg, 3 times a day, for the treatment of seizures during or after neurosurgery, generalized tonic-clonic seizures and complex partial seizures. The maintenance dose is 300 to 400 mg/day, where the maximum dose is 600 mg/day. For the maintenance of status epilepticus in adults, the recommended dose is 100 mg of phenytoin every 6 to 8 hours;
- Children over 6 years old and teenagers: to prevent seizures during or after neurosurgery, the recommended dosage is 5 mg/kg of body weight per day, divided equally into 2 or 3 administrations, with a maximum of 300 mg per day. The usual maintenance dose is 4 to 8 mg/kg of body weight per day.
For elderly people, it is generally recommended to start treatment with 3 mg/kg of body weight per day of phenytoin, in divided doses, increasing according to the concentrations of this medication in the blood and the person’s response.
2. Phenytoin oral suspension 20mg/mL
In adults who have not previously received treatment with phenytoin, it is recommended to start treatment with 5 mL, 3 times a day. If necessary, the daily dose can be increased to 500 mg/day.
In children, the recommended dose is 5 mg/kg of body weight per day, which should be divided into 2 to 3 equal doses and should not exceed the maximum dose of 300 mg/day. Generally, the daily maintenance dose is 4 to 8 mg/kg of body weight per day.
3. Phenytoin Injection 50 mg/mL
The phenytoin injection must be applied directly into the muscle or vein by the nurse, in the hospital, under medical supervision. In children, phenytoin should not be applied to the muscle.
Injectable phenytoin is indicated for adults or children, and the doses must be indicated by the doctor individually according to the condition being treated.
Possible side effects
The most common side effects of phenytoin are nausea, vomiting, diarrhea, abdominal pain, constipation, headache, lack of appetite, tiredness or swollen gums.
In some cases, phenytoin can also cause allergies, causing skin rashes, fever and enlarged lymph nodes, which should be reported immediately to the doctor.
It is also essential to consult a doctor in the presence of mental confusion or severe mental disorder, as this may indicate high levels of phenytoin in the blood.
Phenytoin may cause drowsiness, dizziness, mental confusion, dizziness, visual or attention disturbances, which may impair the ability to drive or operate machines.
Who shouldn’t use
Phenytoin is contraindicated for pregnant or breastfeeding women, and for people allergic to hydantoins or one of the components of this medication.
This medicine should also not be used by people undergoing treatment with delavirdine for HIV, or who use St. John’s wort or contraceptive medicines, analgesics, anti-inflammatories, antibiotics, anticonvulsants, antineoplastics, among others. It is important to always inform your doctor of all medications used.
Furthermore, people with diabetes, thyroid problems, hypotension, heart failure, myocardial infarction, liver or kidney disease or porphyria, or who consume alcoholic beverages, should only take phenytoin under the recommendation of a doctor.
People of Japanese, Thai or Malaysian origin should not take phenytoin, as scientific studies have shown that they have a genetic mutation that is related to the metabolism of some medications, including anticonvulsants.
