Phenobarbitone Pharmacology


About Phenobarbitone
Barbiturate derivative, Sedative-Hypnotic,Anticonvulsant.
Mechanism of Action of Phenobarbitone
Sedative and antiepileptic actions: Phenobarbitone mainly acts on Picrotoxin site of GABA -BZD receptor Cl- (chloride ion) channel complex. It prolongs the duration of GABA induced chloride channel opening and produces hyperpolarisation and decreases firing rate of neurons. This will alters the normal body functions. Phenobarbitone also has GABA mimetic action. At high concentrations Phenobarbitone directly increases chloride ion conductance and decreases transmission of calcium ion (Ca2+ ) dependent neurotransmitters. Phenobarbitone also inhibits excitatory glutamate neurotransmitters. At high concentration it also inhibits sodium ion channel and potassium ion channel. Phenobarbitone is used as an antiepileptic to control partial and generalised tonic-clonic seizures.
Barbiturates activate inhibitory GABA-A receptors and inhibit excitatory AMPA receptors and produces CNS depression.

Pharmacokinets of Phenobarbitone
Absorption: It is well absorbed after oral administration. Distribution: It is widely distributed in the body. Metabolism: It is metabolised in the liver. Excretion: It is excreted mainly through urine.
Onset of Action for Phenobarbitone
1 hour
Duration of Action for Phenobarbitone
10 - 12 hour
Half Life of Phenobarbitone
5 - 7 days
Side Effects of Phenobarbitone
1.Hang over
5.Paradoxical excitement
16 Hypotension
17.Exacerbation of Porphyria
Contra-indications of Phenobarbitone
1.Hypersensitivity to Phenobarbitone and other barbiturates
3.Hepatic impairment
3.Renal impairment
5.Obstructive sleeps apnoea
Special Precautions while taking Phenobarbitone
1.Cardiovascular diseases
2.Patient with acute or chronic pain
4. Alcoholics
5. Drug abuse
6. Shock
7. Debilitated patients
8. Driving vehicles, operating machines and people involving any other dangerous activities
9. Slowly withdraw the drug with caution
Pregnancy Related Information
Use with caution
Old Age Related Information
Use with caution
Breast Feeding Related Information
Children Related Information
Use with caution
Indications for Phenobarbitone
Interactions for Phenobarbitone
Alcohol & other CNS Depressants (other sedatives, hypnotics, anesthetics, antihistamines, tranquilizers, 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, beta-blockers, quinidine, rifampicin, theophylline and metronidazole.
Phenytoin: Effect on phenytoin metabolism is unpredictable.
Frusemide: May produce or aggravate orthostatic hypotension.
Griseofulvin: Interferes with absorption of oral griseofulvin leading to decreased blood levels.
Typical Dosage for Phenobarbitone
Anticonvulsant (Not used for absence and febrile seizure): 60 - 180 mg / day at bed time or 3 divided doses
Sedation: 30 - 120 mg / day in 2 or 3 divided doses
Insomnia: 100 - 200 mg/ day
Maximum dose: 400 mg / day
Anticonvulsant: 1 - 8 mg / kg body weight / day in single dose or 2 divided dose.
Sedation: 8 - 32 mg/ day
Schedule of Phenobarbitone
Storage Requirements for Phenobarbitone
Store at 15 - 25 degree C in a tightly closed container. Keep out of the reach of children.
Effects of Missed Dosage of Phenobarbitone
Take the missed dose as soon as noticed and if it is the time to take the next dose then skip the missed dose.
Effects of Overdose of Phenobarbitone
Give supportive measures and symptomatic treatment. Induce emesis or gastric lavage has to be done. Charcoal can be given to reduce the absorption of the drug. Urine alkalinization also helps to reduce the absorption of the drug. Haemodialysis can be done in severe cases.

Home Delivery for Phenobarbitone in Your City

Medicine India is just a publishing medium for medicine related information and does not provide services or sales of medicines including phenobarbitone.

However, we do publish a comprehensive directory of Pharmacies, Chemists and Druggists in cities all over India. You can use this directory to find the medicine stores in your city (or area) that provide home delivery services for phenobarbitone and other medicines and health products. Home delivery services for phenobarbitone may be free or they may cost you depending on the pharmacy and the minimum order requirements. It would be best to get this clarified while placing the order.

Please be aware that you should take phenobarbitone only if a doctor has recommended or prescribed it. Some or all pharmacies who provide a home delivery service for medicines might insist on a prescription for phenobarbitone before they complete the sale. You can get this information while placing the order for phenobarbitone with the pharmacy.

Phenobarbitone is a generic medicine name and there are several brands available for it. Some of the brands for phenobarbitone might be better known than phenobarbitone itself. If the pharmacy that's willing to deliver medicines to your home doesn't have phenobarbitone in stock, you can ask for one of the branded alternatives for phenobarbitone.