PHENOBARBITAL = PB injectable

Therapeutic action

• Antiseizure (anticonvulsant), sedative

Indications

• Second-line treatment of convulsive status epilepticus

Forms and strengths, route of administration

• 200 mg in 1 ml ampoule (200 mg/ml) for IV infusion in 0.9% sodium chloride
• DO NOT ADMINISTER BY DIRECT IV INJECTION. DO NOT ADMINISTER THE SOLUTION UNDILUTED.
• DO NOT ADMINISTER BY SC INJECTION (risk of necrosis).

Dosage and duration

• Loading dose:
  • Child 1 month and over:
    • Use diluted solution: add 1 ml (200 mg) of PB to 9 ml of 0.9% NaCl to obtain 10 ml of solution containing 20 mg of PB per ml.
    • Administer 20 mg/kg (max. 1 g) over 20 minutes by IV infusion using a syringe pump (or only if not available, using a pediatric infusion set).
    • If seizures do not stop after the end of the first dose, readminister half dose: 10 mg/kg as above.
  • Adult: 
    • 15 mg/kg (max. 1 g) single dose over 15 minutes 
    • Use diluted solution as above (20 mg/ml) if administered by IV infusion using a syringe pump.
    • Use undiluted solution if administered by IV infusion in a bag of 100 ml of 0.9% NaCl. 

Do not exceed an infusion rate of 1 mg/kg/minute in children and 100 mg/minute in adults.

• 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 severe impairment of respiratory, renal or hepatic function (risk of accumulation).
• Administer with caution in children, older patients and patients with mild to moderate impairment of respiratory, renal or hepatic function.
• May cause :
  • drowsiness, dizziness, headache, behavioural disturbances;
  • dose-dependant respiratory depression;
  • hypotension, apnoea, laryngospasm, shock, especially if administered rapidly by IV route and if large doses are administered;
  • haematologic disorders, gastrointestinal disturbances;
  • hypersensitivity reactions sometimes severe;
  • coma in the event of overdose.
• Monitor closely respiratory rate and blood pressure during and after administration.
• Avoid or monitor the combination with:
  • mefloquine (reduced effect of PB);
  • benzodiazepines, opioid analgesics, antipsychotics, first-generation antihistamines (hydroxyzine, promethazine), antidepressants, other antiseizure medications, etc. (increased sedation).
• Use with extreme caution with benzodiazepines and opioids analgesics (increased risk of respiratory depression).
• PB may reduce the effect of many drugs:
  • diazepam, midazolam, antimicrobials, some antiretrovirals, corticosteroids, tricyclic antidepressants, itraconazole, direct-acting antivirals for chronic hepatitis C, warfarin, etc. Adjust dosage if necessary.
  • implants and oral contraceptives: use condoms until next menstruation.
• Pregnancy and breast-feeding: prefer a safer drug (levetiracetam). If PB is the only option, the risks linked to status epilepticus appear greater than risks linked to PB.

Remarks

• PB is subject to international controls: follow national regulations.
• Do not mix with other drugs in the same syringe or infusion.

Storage