PHENOBARBITONE

Indications & Dose:

All forms of epilepsy except typical absence seizures

•  BY MOUTH

Child 1 month–11 years: Initially 1– 1.5 mg/kg twice daily, then increased in steps of 2 mg/kg daily as required; maintenance 2.5–4 mg/ kg 1–2 times a day

Child 12–17 years: 60–180 mg once daily

Adult: 60–180 mg once daily, dose to be taken at night

Status epilepticus

• BY INTRAVENOUS INJECTION

Adult: 10 mg/kg (max. per dose 1 g), dose to be administered at a rate not more than 100 mg/minute, injection to be diluted 1 in 10 with water for injections

• BY SLOW INTRAVENOUS INJECTION

Child 1 month–11 years: Initially 20 mg/kg, dose to be administered at a rate no faster than 1 mg/kg/minute, then 2.5–5 mg/kg 1–2 times a day Child 12–17 years: Initially 20 mg/kg (max. per dose 1 g), dose to be administered at a rate no faster than 1 mg/kg/minute, then 300 mg twice daily 

Contraindications:

Barbiturates are contraindicated in Acute Intermittent Porphyria, uncontrolled pain and debilitated individuals and in cases of alcohol and drug abuse. Hyperkinetic children. 

Side Effects:

Main side effect is sedation (which disappears after a few weeks due to development of tolerance). In young and elderly, causes confusion and paradoxical excitement or agitation. Irritability and hyperactivity in children may be seen. Megaloblastic anaemia, osteomalacia and skin rashes may occur. Rarely hepatitis and agranulocytosis may occur. The toxicity is manifested by hypotension, ataxia, dizziness, respiratory depression, coma and death

Cautions:

Precautions:

Chronic use of barbiturates may result in intolerance and drug dependence. Barbiturates cause decreased efficacy of other drugs because of hepatic microsomal enzyme induction in liver and accelerated metabolism of oral anticoagulants, oral contraceptives and phenytoin. Respiratory insufficiency.

Pregnancy & Breastfeeding: use with caution.

Old age: may be given in reduced dose. 

Interaction:

Drugs Alcohol and other CNS Depressants (other sedatives, Hypnotics, Anesthetics, Antihistamines, Tranquillizers, Phenothiazines): Additive CNS depression.

Valproic acid: Increases efficacy of barbiturates. Half life of valproic acid may be decreased.

Chloramphenicol: Efficacy of barbiturates increased.

Barbiturates may decrease  efficacy of chloramphenicol.

MAOIs: Effects of barbiturates prolonged.

Efficacy of the following drugs decreased by barbiturates: Oral anticoagulants, Digitoxin, TCAs, Corticosteroids, Doxycycline, Oral contraceptives and estrogens, Acetaminophen, ß-Blockers, Quinidine, Rifampicin, theophylline and Metronidazole.

Phenytoin: Effect on phenytoin metabolism is unpredictable.

Furosemide: May produce or aggravate orthostatic hypotension.

Griseofulvin: Interferes with absorption of oral griseofulvin leading to decreased blood levels. 

Warnings:

Adverse Effects:

Lactations:

Special Precautions:

Counselling:

Side Effects Or Adverse Reactions:

Patient And Carer Advice: