Mixed evidence on the risk of switching
Currently, several TMS devices are FDA-cleared for treating unipolar major depressive disorder, obsessive-compulsive disorder, and certain types of migraine. In March 2020, the FDA granted Breakthrough Device Designation for one TMS device, the NeuroStar Advanced Therapy System, for the treatment of bipolar depression.8 This designation created an expedited pathway for prioritized FDA review of the NeuroStar Advanced Therapy clinical trial program.
Few published clinical studies have evaluated using TMS to treat patients with bipolar depression.9-15 As with any antidepressant treatment for bipolar depression, there is a risk of affective switch from depression to mania when using TMS. Most of the literature available regarding the treatment of bipolar depression focuses on the risk of antidepressant medications to induce an affective switch. This risk depends on the class of the antidepressant,16 and there is a paucity of studies examining the risk of switch with TMS.
Interpretation of available literature is limited due to inconsistencies in the definition of an affective switch, the variable length of treatment with antidepressants, the use of concurrent medications such as mood stabilizers, and confounders such as the natural course of switching in bipolar disorder.17 Overall, the evidence for treatment-emergent mania related to antidepressant use is mixed, and the reported rate of treatment-emergent mania varies. In a systematic review and meta-analysis of >20 randomized controlled trials that included 1,316 patients with bipolar disorder who received antidepressants, Fornaro et al18 found that the incidence of treatment-emergent mania was 11.8%. It is generally recommended that if antidepressants are used to treat patients with bipolar disorder, they should be given with a traditional mood stabilizer to prevent affective switches, although whether mood stabilizers can prevent such switches is unproven.19
In a literature review by Xia et al,20 the affective switch rate in patients with bipolar depression who were treated with TMS was 3.1%, which was not statistically different from the affective switch rate with sham treatment.However, most of the patients included in this analysis were receiving other medications concurrently, and the length of treatment was 2 weeks, which is shorter than the average length of TMS treatment in clinical practice. In a recent literature review by Rachid,21 TMS was found to possibly induce manic episodes when used as monotherapy or in combination with antidepressants in patients with bipolar depression. To reduce the risk of treatment-emergent mania, current recommendations advise the use of a mood stabilizer for a minimum of 2 weeks before initiating TMS.1
In our case, Ms. W was receiving antidepressants (fluoxetine and trazodone), lurasidone (an SGA that is FDA-approved for bipolar depression), and methylphenidate before starting TMS treatment. Fluoxetine, trazodone, and methylphenidate may possibly contribute to an increased risk of an affective switch.1,22 Further studies are needed to clarify whether mood stabilizers or SGAs can prevent the development of mania in patients with bipolar depression who undergo TMS treatment.20
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