Primidone Pharmacology

Primidone

About Primidone

Pyrimidinedione derivative,deoxybarbiturate, Anticonvulsant.

Mechanism of Action of Primidone

Primidone is a Deoxybarbiturate. In the liver Primidone is metabolised to active metabolites Phenobarbitone and Phenylethylmalonamide (PEMA). The anticonvulsant activity is mainly due to these metabolites. 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. Thus due to the presence of active metabolites Primidone is used as an antiepileptic to control partial and generalised tonic-clonic seizures.

Pharmacokinets of Primidone

Absorption: Primidone is absorbed after oral administration. Distribution: It is distributed widely throughout the body. Metabolism: It is metabolised in the liver to Phenobarbitone and Phenylethylmalonamide (PEMA). Excretion: Excreted mainly in urine. Drug is also excreted through faeces and breast milk.

Onset of Action for Primidone

Within 60 minutes

Duration of Action for Primidone

1 day

Half Life of Primidone

6 - 14 hours

Side Effects of Primidone

1. Drowsiness
2. Ataxia
3. Nausea
4. Vomiting
5. Blurred vision
6. Anaemia
7. Sedation
8. Headache
9. Irritability

Contra-indications of Primidone

1. Hypersensitivity to Primidone
2. Porphyria

Special Precautions while taking Primidone

1. Hepatic impairment
2. Renal disease
3. Respiratory diseases
4. Slowly withdraw the drug with caution
5. Patient should be cautioned about driving a car, operating a car or work requiring mental alertness

Pregnancy Related Information

Use with caution

Old Age Related Information

Use with caution

Breast Feeding Related Information

Use with caution

Children Related Information

Use with caution
NEONATES: Contraindicated

Indications for Primidone

Anticonvulsants

Interactions for Primidone

Acetazolamide: May decrease concentration of primidone.
Carbamazepine: Efficacy of primidone, phenobarbital decreased and serum concentration of carbamazepine increased.
Hydantoins: Concentrations of primidone and its metabolites phenobarbital and PEMA may be increased.
Isoniazid: Primidone concentration may be enhanced.
Nicotinamide: Clearance rate of primidone may be decreased.

Typical Dosage for Primidone

Adult: 100 - 125 mg at bed time. Increase the dose by 100 - 125 mg every 3 days up to 500 mg / day. If sufficient response dose not occur dose can be again increased by 250 mg every 3 days up to 2g / day.
Maintenance dose: 250 mg 3 - 4 times daily.
Children (above 8 years): 100 - 125 mg at bed time. Increase the dose by 100 - 125 mg every 3 days up to 500 mg / day. If sufficient response dose not occur dose can be increased by 250 mg every 3 days up to 2g / day.
Maintenance dose: 250 mg 3 - 4 times daily
Children (6 - 8 years): 50mg at bed time for 1 - 3 days.Then increase the dose to 100 mg / day in 2 divided dose for 4 - 6 days. Then again incease the dose to 200 mg / day in 2 divided dose for 7 - 9 days.
Maintenance dose: 375 -750 mg/ day in 3 divided doses

Schedule of Primidone

Storage Requirements for Primidone

Store at room temperature in a tightly closed container. Protect from direct light and heat. Keep out of the reach of children.

Effects of Missed Dosage of Primidone

Take the missed dose as soon as noticed and if it is the time for next dose then skip the missed dose. Do not double the dose.

Effects of Overdose of Primidone

Give supportive measures and symptomatic treatment. Drug can be removed from the body by emesis or gastric lavage. Alkalinization of urine and forced diuresis enhances the excretion of the drug from the body. Absorption of the drug can be reduced by administration of activated charcoal. Haemodialysis can be done if necessary.

Home Delivery for Primidone in Your City

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

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 primidone and other medicines and health products. Home delivery services for primidone 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 primidone 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 primidone before they complete the sale. You can get this information while placing the order for primidone with the pharmacy.

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