It is given that medical illness is common in psychiatric patients and that psychiatric pathology is common in medical conditions. Within the emergency department, psychiatric patients make-up one of the major diagnostic categories. Evaluation of pre-existing and comorbid psychiatric conditions and their treatments, which can have a profound impact on the patient's medical evaluation, differential diagnosis, and treatment plan, should quickly follow stabilization of the emergency condition. According to the NIMH Epidemiologic Catchment Area Program, more than half of those that abuse drugs have a psychiatric comorbidity with an odds ratio of 4.5. Polypharmacy is a growing national problem, not just in the comorbid medical-psychiatric patient, and is noted especially in select patient populations like nursing homes, a growing referral source for many emergency departments. Psychiatric patients are often taking adjunctive medications such as tricyclic antidepressants, anticonvulsants, and benzodiazepines that can be adjusted to serve dual therapeutic purpose.