PHENYTOIN injectable

Prescription under medical supervision

Therapeutic action

– Anticonvulsant


– Emergency treatment of convulsive status epilepticus

Presentation and route of administration

– 250 mg in 5 ml ampoule (50 mg/ml) for infusion in 0.9% sodium chloride. DO NOT DILUTE IN GLUCOSE.

Dosage and duration

– Child 1 month and over and adult: one dose of 15 to 20 mg/kg to be administered over 20 minutes minimum and 60 minutes maximum
– The concentration of the diluted solution should be between 5 and 10 mg/ml. The infusion rate should not exceed 1 mg/kg/minute or 50 mg/minute (25 mg/minute in elderly patients or patients with cardiac disorders). 
For example:
Child weighing 8 kg: 160 mg (20 mg x 8 kg), i.e. 3.2 ml of phenytoin in 17 ml of 0.9% sodium chloride over 30 minutes
Adult weighing 50 kg: 1 g (20 mg x 50 kg), i.e. 20 ml of phenytoin in a bag of 100 ml of 0.9% sodium chloride over 30 minutes

Contra-indications, adverse effects, precautions

– Do not administer in patients with bradycardia, atrioventricular block.
– Administer with caution in patients with hepatic impairment (reduce dosage), heart failure, cardiac rhythm disorders, hypotension.
– Administer with caution in patients taking:
• sulfonamides, chloramphenicol, fluconazole, isoniazid, fluoxetine (effects of phenytoin increased);
• rifampicin , ciprofloxacin, ritonavir, folic acid (effects of phenytoin decreased).
– May cause:
• hypotension, bradycardia, conduction disorders, depression of the central nervous system when administered too quickly;
• irritation or swelling at injection site; necrosis in the event of extravasation;
• decreased coordination, confusion, dizziness, headache, nausea, vomiting; 
• hepatotoxicity; haematologic disorders; allergic and cutaneous reactions, sometimes severe.
– Use a large catheter.
– Monitor closely heart rate, blood pressure and respiratory rate during and after administration. Reduce the infusion rate in the event of a drop in blood pressure or bradycardia.
– For women taking estroprogestogen, use condoms until next menstruation (decreases the efficacy of the contraceptive).
– Pregnancy and breast-feedingrisks related to status epilepticus are greater than risks related to phenytoin.


– Never dilute phenytoin in glucose (risk of precipitation).
– After each infusion, rinse with 0.9% sodium chloride to limit local venous irritation due to alkaline pH of phenytoin.
– Do not mix with other drugs in the same infusion.
– Storage: below 25 °C - 
If refrigerated a deposit may form in the solution that later dissolves at room temperature. Check the solution is completely clear before administration.