<prompt>  A patient who is being treated for temporal lobe epilepsy complex partial seizures and who is having recurrent seizures on his chronic regimen of carbamazepine is given phenobarbital as a second drug. However, the seizures increase in frequency. What is the probable reason for the apparent deleterious effect of adding phenobarbital -Intracerebral bleeding from worsening bone marrow supressionDecreased carbamazepine levelDecreased stability of CNS neuronal membranesHypokalemia 