A dvances in the understanding of neurobiological and neuro psychiatric pathophysiology have opened new avenues of treatment for psychiatric patients. Historically, with a few exceptions, most psychiatric medications have been administered orally. However, many of the newer treatments require some form of special ized administration because they cannot be taken orally due to their chemical property (such as aducanumab); because there is the need to produce stable blood levels of the medication (such as brexanolone); because oral administration greatly diminished efficacy (such as oral vs IV magnesium or scopolamine), or because the treatment is focused on specific brain structures. This need for specialized administration has created a subspecialty called interventional psychiatry.Part 1 of this 2part article provides an overview of 1 type of inter ventional psychiatry: parenterally administered medications, includ ing those administered via IV. We also describe 3 other interventional approaches to treatment: stellate ganglion blocks, glabellar botulinum toxin (BT) injections, and trigger point injections. In Part 2 we will review interventional approaches that involve neuromodulation. Parenteral medications in psychiatryIn general, IV and IM medications can be more potent that oral medica tions due to their overall faster onset of action and higher blood con centrations. These more invasive forms of administration can have significant limitations, such as a risk of infection at the injection site, the need to be administered in a medical setting, additional time, and patient discomfort.

While most psychiatric treatments have traditionally consisted of pharmacotherapy with oral medications, a better understanding of the pathophysiology underlying many mental illnesses has led to the recent increased use of treatments that require specialized administration and the creation of a subspecialty called interventional psychiatry. In Part 1 of this 2-part article ("Interventional psychiatry [