Phenytoin Sodium Tablets

Oral absorption is slow, 85-90% is absorbed by the small intestine, the absorption rate varies greatly from person to person and is affected by food. Newborns absorb very poorly. Oral bioavailability is about 79%, distributed in intracellular and extracellular fluids, and the intracellular content may be more than the extracellular content, with an apparent distribution volume of 0.6L/kg. The plasma protein binding rate is 88-92%, mainly bound to albumin, and the protein binding in brain tissue may be even higher. The blood concentration reaches its peak 4-12 hours after oral administration. It is mainly metabolized in the liver, and the metabolites are pharmacologically inactive, mainly hydroxyphenytoin (accounting for about 50-70%). This metabolism has genetic polymorphism and racial differences. There is an enterohepatic circulation, which is mainly excreted through the kidneys, and alkaline urine excretion is faster. T1/2 is 7-42 hours. For patients who take phenytoin sodium for a long time, T1/2 can be 15-95 hours, or even longer. After a certain dose of the drug is applied, the liver metabolism (hydroxylation) capacity reaches saturation. At this time, even if the dose is increased by a small amount, the blood concentration increases nonlinearly and sharply, and there is a risk of poisoning. The blood concentration should be monitored. The effective blood concentration is 10~20mg/L. Oral administration of 300mg daily can reach a steady-state concentration in 7~10 days. When the blood concentration exceeds 20mg/L, toxic reactions are likely to occur, such as nystagmus; when it exceeds 30mg/L, ataxia occurs; when it exceeds 40mg/L, serious toxic effects often occur. It can pass through the placenta and can be secreted into breast milk.

The main ingredient of this product is phenytoin sodium, its chemical name is: 5,5-diphenyl-2,4-imidazolidinedione sodium salt, chemical structure formula is: Molecular formula: C15H11N2NaO2 Molecular weight: 274.25

This product is white tablets or film-coated tablets.

It is suitable for the treatment of generalized tonic-clonic seizures, complex partial seizures (psychomotor seizures, temporal lobe epilepsy), simple partial seizures (localized seizures) and status epilepticus. It can also be used to treat trigeminal neuralgia, recessive dystrophic epidermolysis bullosa, paroxysmal choreoathetosis, paroxysmal control disorders (including behavioral disorders such as anger, anxiety and insomnia due to excessive excitement), myotonia and cardiac conduction disorders in case of overdose of tricyclic antidepressants. This product is also suitable for ventricular and supraventricular arrhythmias caused by digitalis poisoning, and has poor efficacy on arrhythmias caused by various other reasons.

Common dosage for anti-epileptic drugs in adults: 250~300mg per day, 100mg at the beginning, twice a day, increase to 250~300mg within 1~3 weeks, divided into three times for oral administration, the maximum dose is 300mg once, 500mg per day. Due to individual differences and saturated pharmacokinetic characteristics, medication needs to be individualized. After the application achieves control of seizures and the blood drug concentration reaches a steady state, a long-acting (controlled release) preparation can be used instead, which is taken at once. If the seizures are frequent, 12~15mg/kg can be taken in 2~3 times, once every 6 hours, and 100mg (or 1.5~2mg/kg according to body weight) can be given from the next day, 3 times a day until the appropriate dose is adjusted. Common dosage for children: 5mg/kg per day, divided into 2~3 times, adjusted as needed, and not more than 250mg per day. The maintenance dose is 4~8mg/kg or 250mg/m2 according to body surface area, divided into 2~3 times, and blood drug concentration monitoring can be performed if conditions permit. Commonly used dosage for antiarrhythmic adults: 100-300 mg, taken once or divided into 2-3 times, or 10-15 mg/kg on the first day, 7.5-10 mg/kg on the second to fourth day, and maintenance dose of 2-6 mg/kg. Common dosage for children: Start with 5 mg/kg of body weight, divided into 2-3 times orally, and adjust the daily dosage to no more than 300 mg according to the condition, and the maintenance dosage is 4-8 mg/kg, or divided into 2-3 times orally according to the body surface area of 250 mg/m2. Common dosage for collagenase synthesis inhibitors for adults starts with 2-3 mg/kg daily, divided into 2 times, and within 2-3 weeks, increase to the dosage that the patient can tolerate, and the blood drug concentration reaches at least 8 μg/ml. Generally 100-300 mg per day.

This product has few side effects, common gingival hyperplasia, and a high incidence in children. Oral hygiene and gingival massage should be strengthened. After long-term use or when the blood drug concentration reaches 30mu;g/ml, it may cause nausea, vomiting and even gastritis, which can be alleviated by taking it after meals. Adverse reactions of the nervous system are related to the dose. Common dizziness and headaches can cause nystagmus, ataxia, slurred speech and confusion in severe cases. Adjusting the dose or stopping the drug can eliminate them; less common adverse reactions of the nervous system include dizziness, insomnia, transient nervousness, twitches, chorea, dystonia, tremor, asterixis, etc. It can affect the hematopoietic system, causing granulocytopenia and thrombocytopenia, and rare aplastic anemia; common megaloblastic anemia can be prevented and treated with folic acid and vitamin B12. It can cause allergic reactions, common rashes with high fever, and rare severe skin reactions, such as exfoliative dermatitis, multiform erosive erythema, systemic lupus erythematosus and fatal liver necrosis, Hodgkin's disease of the lymphatic system, etc. Stop the drug immediately and take appropriate measures if symptoms appear. Long-term use in children can accelerate vitamin D metabolism and cause rickets or bone abnormalities. Use by pregnant women can occasionally cause teratogenesis. It can inhibit the secretion of antidiuretic hormone and insulin, causing blood sugar to rise, and there have been reports of it causing cancer.

Contraindications: Patients with a history of allergy to hydantoins or those with heart function impairment such as Ass syndrome, II-III degree atrioventricular block, sinus node block, sinus bradycardia, etc.

Precautions for children: Since the distribution volume and elimination half-life of children change with age, blood drug concentration should be measured frequently. The pharmacokinetics of this product are special for neonates or infants, and it is difficult to clinically assess the symptoms of poisoning. It is generally not used first. Preschool children have strong liver metabolism, and blood drug concentration needs to be monitored multiple times to determine the frequency and dosage of medication. Precautions for pregnancy and lactation: This product can pass through the placenta and may cause teratogenesis, but it is believed that the risk of teratogenesis due to uncontrolled epileptic seizures is greater than the risk of medication. The pros and cons should be weighed. Patients who can control seizures with this product should continue to take it during pregnancy and maintain blood concentration, and then readjust after delivery. Vitamin K should be supplemented one month before delivery, and vitamin K should be injected into the newborn immediately after delivery to reduce the risk of bleeding. This product can be secreted into breast milk, and it is generally recommended that mothers taking phenytoin sodium avoid breastfeeding. Precautions for the elderly: The incidence of chronic hypoproteinemia in the elderly is high, and there are many combined medications in treatment, and the interactions between drugs are complex. Be cautious when using this product, and the dosage should be low. And monitor blood drug levels frequently.

1. Long-term use of acetaminophen in patients may increase the risk of liver poisoning and reduce the efficacy. 2. It is a liver enzyme inducer. When used in combination with corticosteroids, digitalis (including digoxin), oral contraceptives, cyclosporine, estrogen, levodopa, quinidine, oxytetracycline or tricyclic antidepressants, the effects of these drugs may be reduced. 3. Long-term drinking can reduce the concentration and efficacy of this product, but drinking a lot of alcohol while taking the medicine can increase the blood concentration; combined with chloramphenicol, isoniazid, phenylbutazone, and sulfonamides may reduce the metabolism of this product and increase the blood concentration and toxicity of this product; combined with anticoagulants, the anticoagulant effect will increase at the beginning, but it will decrease with continuous use. 4. When used in combination with magnesium, aluminum or calcium carbonate, the bioavailability of this product may be reduced. The two should be taken 2 to 3 hours apart. 5. When used in combination with hypoglycemic drugs or insulin, because this product can increase blood sugar, the dosage of the latter two needs to be adjusted. 6. In principle, patients who use dopamine should not use this product. 7. This product may enhance the inhibitory effect on the heart when used in combination with lidocaine or propranolol. 8. Although this product consumes folic acid in the body, increasing folic acid can reduce the concentration and effect of this product. 9. The effect of phenobarbital or primidone on this product varies greatly, and the blood concentration should be monitored frequently; when used in combination with valproic acid, there is a protein binding competition, and the blood concentration should be monitored frequently to adjust the dosage of this product. 10. When used in combination with carbamazepine, the latter's blood concentration is reduced. If a large amount of antipsychotics or tricyclic antidepressants are used in combination, epileptic seizures may occur, and the dosage of this product needs to be adjusted.

Light-proof, sealed

0.1 g

36 months

NORTHEAST Pharmaceutical Group Shenyang NO.1 Pharmaceutical Co., Ltd.

• Founded in:

  1989-01-25

• Address:

  No. 8 Kunming Lake Street, Shenyang Economic and Technological Development Zone

• Tax NO.:

  91210106242656694M

• Registered Funds:

  80 million yuan

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