A patient who is being treated for temporal lobe epilepsy (complex paial 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:
Answer is B (Decreased Carbamazepine levels): Phenobarbitone is a microsomal enzyme inducer so administration of phenobarbitone induces the metabolism of carbamazepine and reduces its level in blood.
Intracerebral bleeding from worsening bone marrow suppression
Decreased carbamazepine level
Decreased stability of CNS neuronal membranes
Hypokalemia