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Drug Information
Pharmacokinetics
| Indication
& Dosage | Action
| Interacations |
Adverse
Effects & Precautions |
Brands available in Market
Primidone is readily absorbed from
the gastrointestinal tract and is reported to have a plasma half-life
ranging from 10 to 15 hours, which is shorter than those of its
principal metabolites phenylethylmalonamide and phenobarbitone, both of
which are active. It is excreted in urine as unchanged drug (40%) and
metabolites.
Primidone is widely distributed but is only partially bound to plasma
protein; it has been suggested that it exhibits variable binding of up
to about 20%. It crosses the placenta and is distributed into breast
milk.
Indication
& Dosage
Oral
TONIC-CLONIC (GRAND MAL) AND PARTIAL ESPECIALLY PSYCHOMOTOR SEIZURES:
Start wiht 125mg daily in late evenings. Increase if necessary, by 125mg
every 3 days upto 500mg/day. Further increments of 250mg given upto1.5g
in adults Children: Upto 2yrs-250-500mg daily. 2-5 yrs-500-750mg daily.
6-9yrs-0.75-1.0g daily. 6-9yrs-0.75-1.0g daily. Maintenance doses for
adults and children may be given in 2 divided doses
ESSENTIAL TREMOR: 50mg daily increasing gradually upto 750mg daily.
Action
Raise seizure thresholds. Partly metabolised to
phenobarbitone which also exerts anticonvulsant activity.
Primidone is metabolised in the body in part to phenobarbitone and interactions recorded for phenobarbitone might potentially occur in patients receiving primidone. In addition, enzyme-inducing drugs enhance this metabolism and have the potential to produce elevated phenobarbitone concentrations.
Adverse Effect & Precautions
Serious toxicity is rarely seen. Hedache, sedation, drowsiness,
irritability, anaemia and impairment of higher intellectual functions
may occur.
Precaution: Respiratory
disease, hepatic and renal diseases. Simulataneous administration of
primidone with alcohol and CNS depressants should be avoided. Sodium
valproate may inhibit the metabolism of primidone with alcohol and CNS
depressnats should be avoided. Sodium valproate may inhibit the
metabolism of primidone. Abrupt withdrawal. Children.
Pregnancy: Use with caution.
Breast Feeding: Use with caution.
Man: May be given in reduced dose
