Phenobarbital Question

Bella had her appointment with Dr T today. Her phenobarb level is 27 umol/L which is well below the therapeutic range which starts at 41 umol/L. Her dose is now 1.8 mg/kg which is also below the normal dose. We are going to speed up the weaning process slightly and she will be off the Phenobarb by the end of December. Even though the level is so low I still worry that it may be having some therapeutic effect at these levels. When Bella was on Phenobarb monotherapy she needed a level over 100 umol/L  and a dose of 10 mg/kg for seizure control so I am hoping that it is not still contributing to seizure control at these levels. Does anyone know if there could still be a therapeutic benefit at these low levels?

On a lighter note Bella is pulling herself up into standing which is a great new achievement.....