PHENOBARBITAL AND VALPROATE
Serum phenobarbital levels can be increased by sodium valproate. Small reductions in sodium valproate levels have also been reported. Valproate has been reported to cause increases, decreases, and no change in serum primidone levels. Primidone-derived phenobarbital levels appear to be increased by valproate. Combined use of phenobarbital and valproate may cause an increase in serum liver enzymes.
Use of this combination may result in excessive sedation and lethargy. To control this interaction the dosage of phenobarbital has been reduced by about 30 to 50%, without loss of seizure control. Indicators of phenobarbital toxicity include drowsiness, ataxia or dysarthria. Monitor levels as necessary. Valproate has been associated with serious hepatotoxicity, especially in children aged less than 3 years, and this has been more common in those receiving other antiepileptics. Valproate monotherapy is to be preferred in this group.
Use of this combination may result in excessive sedation and lethargy. To control this interaction the dosage of phenobarbital has been reduced by about 30 to 50%, without loss of seizure control. Indicators of phenobarbital toxicity include drowsiness, ataxia or dysarthria. Monitor levels as necessary. Valproate has been associated with serious hepatotoxicity, especially in children aged less than 3 years, and this has been more common in those receiving other antiepileptics. Valproate monotherapy is to be preferred in this group.