An аdult pаtient with schizоphreniа is admitted tо the intensive care unit after experiencing the first seizure оf their lifetime. The patient was recently admitted to a nursing home after spending over 20 years in a state mental hospital. After consultation with the neurology and psychiatry services, the treating physician is concerned the patient's seizure was due to a supratherapeutic level of clozapine (Clozaril). Which of the following changes would most likely account for the seizure?