Dexmedetomidine is an alpha-2 agonist commonly used during neurosurgery due to its unique properties as a sedative and anxiolytic with minimal respiratory depression. Neurosurgical patients frequently come to the operating room on anticonvulsant therapy with a history of seizures. The investigators clinical experience suggests that these patients are resistant to the sedative effects of dexmedetomidine. This effect may represent a pharmacokinetic interaction between the anticonvulsant medications and dexmedetomidine or the higher dexmedetomidine dose requirement could result from abnormal pharmacodynamics due to the underlying seizure disorder. The investigators study aims to investigate the pharmacokinetic and pharmacodynamic differences of dexmedetomidine between patients receiving and not receiving enzyme-inducing anticonvulsant therapy and to identify a potential mechanism for these differences.