Phenobarbital is probably at present the most widely used medicinal agent in the treatment of convulsive states. Inasmuch as its action is merely palliative, treatment is often prolonged or continued indefinitely. An inadequate dose is usually prescribed by the general practitioner, as he fears toxic effects. Therefore phenobarbital is frequently in disrepute with the patient before he comes to the specialist. Textbooks also are conservative with regard to this drug. Though the virtues of phenobarbital are admitted, the hazards are too often overemphasized.
In our experience in 600 cases of convulsive states, large doses of phenobarbital have often been necessary to keep patients free from seizures. Yet we have never encountered an instance of serious idiosyncrasy to the drug. Mental deterioration does occur in a variable percentage of epileptic patients,1 and it is conceivable that chronic intoxication with drugs may be partly responsible for intellectual impairment in some patients
SOMERFELD-ZISKIND E, ZISKIND E. EFFECT OF PHENOBARBITAL ON THE MENTALITY OF EPILEPTIC PATIENTS. Arch NeurPsych. 1940;43(1):70-79. doi:10.1001/archneurpsyc.1940.02280010078005