Phenytoin = PHT injectable

Therapeutic action

Antiseizure (anticonvulsant).

Indications

Second-line treatment of convulsive status epilepticus.

Forms and strengths, route of administration

This drug should only be used by well-trained personnel in well-equipped hospitals.

During and after administration, have ventilation equipment and solutions for fluid replacement ready for use.

• 250 mg in 5 ml ampoule or vial (50 mg/ml), for IV route only, to be administered through a large central or peripheral vein.
• Dilute the solution in 0.9% sodium chloride only. Do not dilute in glucose.
• For administration use an infusion set or line with a 0.2 micron filter.
• Do not administer by rapid IV injection.

Dose and duration

Child and adult: 20 mg/kg, maximum 2 g, single dose.

• Children 1 month and over and 25 kg or less: add 1 ml (50 mg) of PHT to 9 ml of 0.9% sodium chloride to obtain 10 ml of solution containing 5 mg/ml. Administer by IV infusion using a syringe pump over 20 minutes, maximum 1 mg/kg/minute.
• Children over 25 kg and adults: add undiluted solution to a 100 ml bag of 0.9% sodium chloride and administer by IV infusion. Up to 1 g or up to 50 kg over 20 minutes, max. rate 50 mg/minute. More than 1 g to 1.5 g or over 50 to 75 kg over 30 minutes. More than 1.5 g to 2 g or over 75 to 100 kg over 40 minutes.
• Older patients 65 years and over and adults with cardiac disorders: use undiluted solution in a 100 ml bag of 0.9% sodium chloride and administer over longer durations, with a maximum rate of 25 mg/minute.
• If maintenance treatment is indicated after the loading dose, change to oral route as soon as possible.

Contra-indications, adverse effects, precautions

• Do not administer to patients with bradycardia or atrioventricular block.
• Administer with caution in patients with hepatic impairment, with dose reduction, heart failure, cardiac rhythm disorders, or hypotension.
• May cause irritation or swelling at injection site, necrosis in the event of extravasation, drowsiness, dizziness, headache, behavioural disturbances, hypotension, bradycardia, conduction disorders, gastrointestinal disturbances, hepatotoxicity, haematologic disorders, hypersensitivity reactions, and cardiac complications or coma in overdose.
• Closely monitor heart rate and blood pressure during and after administration. Reduce the infusion rate in the event of bradycardia or drop in blood pressure.
• Avoid IV placement in the hand, foot, or wrist, and closely monitor the injection site, especially in older or very young patients and in patients with cardiovascular disease.
• Before and after infusion, flush the catheter with 0.9% sodium chloride to limit venous irritation and incompatibility with other drugs.
• Avoid or monitor combination with rifampicin, mefloquine, sulfonamides, chloramphenicol, fluconazole, isoniazid, fluoxetine, omeprazole, benzodiazepines, opioid analgesics, antipsychotics, first-generation antihistamines, antidepressants, and other antiseizure medications.
• Phenytoin may reduce the effect of many drugs including diazepam, midazolam, digoxin, corticosteroids, antimicrobials, some antiretrovirals, itraconazole, and warfarin.
• Implants and oral contraceptives: use condoms until next menstruation.
• Pregnancy and breast-feeding: prefer a safer drug such as levetiracetam. If phenytoin is the only option, the risks linked to status epilepticus appear greater than the risks linked to phenytoin.
• Do not mix with other drugs in the same syringe or infusion.