Interventional psychiatry (Part 1)

Advances in the understanding of neurobiological and neuro­psychiatric 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 specialized 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 2-part article provides an overview of 1 type of interventional psychiatry: parenterally administered medications, including 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 psychiatry

In general, IV and IM medications can be more potent that oral medications due to their overall faster onset of action and higher blood concentrations. 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.

Table 1 lists short-acting injectable medications used in psychiatry, and Table 2 lists long-acting injectable medications. Parenteral administration of antipsychotics is performed to alleviate acute agitation or for chronic symptom control. These medications generally are not considered interventional treatments, but could be classified as such due to their invasive nature.¹ Furthermore, inhalable loxapine—which is indicated for managing acute agitation—requires a Risk Evaluation and Mitigation Strategy program consisting of 2 hours observation and monitoring of respiratory status.^2,3 Other indications for parenteral treatments include IM naltrexone extended release⁴ and subcutaneous injections of buprenorphine extended release⁵ and risperidone.⁶

IV administration

Most IV treatments described in this article are not FDA-approved for psychiatric treatment. Despite this, many interventional psychiatric treatments are part of clinical practice. IV infusion of ketamine is the most widely known and most researched of these. Table 3 lists other IV treatments that could be used as psychiatric treatment.

Ketamine

Since the early 1960s, ketamine has been used as a surgical anesthetic for animals. In the United States, it was approved for human surgical anesthesia in 1970. It was widely used during the Vietnam War due to its lack of inhibition of respiratory drive; medical staff first noticed an improvement in depressive symptoms and the resolution of suicidal ideation in patients who received ketamine. This led to further research on ketamine, particularly to determine its application in treatment-resistant depression (TRD) and other conditions.⁷ IV ketamine administration is most widely researched, but IM injections, intranasal sprays, and lozenges are also available. The dissociative properties of ketamine have led to its recreational use.⁸

Hypotheses for the mechanism of action of ketamine as an antidepressant include direct synaptic or extrasynaptic (GluN2B-selective), N-methyl-D-aspartate receptor (NMDAR) inhibition, selectively greater inhibition of NMDARs localized on GABAergic (gamma-aminobutyric acid) interneurons, and the role of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor activation. There are links between ketamine’s antidepressant actions and downstream mechanisms regulating synaptic plasticity, including brain-derived neurotrophic factor, eukaryotic elongation factor 2, mammalian target of rapamycin, and glycogen synthase kinase-3. Multiple other ketamine-associated mechanisms also have been described.^9,10 Action on the mu-opioid receptor is also known, possibly contributing to both antidepressant and anesthetic properties of ketamine.¹¹ Rapid onset of ketamine antidepressant action is especially valuable.¹²

Continue to: Ketamine is a schedule...