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Olanzapine-samidorphan combination for schizophrenia or bipolar I disorder

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Approved by the FDA on May 28, 2021, olanzapine-samidorphan combination (OSC) (Lybalvi, manufactured and distributed by Alkermes, Inc. Waltham, MA USA) is intended to help mitigate some of the weight gain that can be anticipated with the use of olanzapine alone (Table).1-3 Olanzapine (Zyprexa, originally manufactured and distributed by Eli Lilly and Company/Lilly USA, LLC, Indianapolis, IN USA) is a second-generation antipsychotic that has been available for a quarter century.4 Although highly efficacious,5,6 olanzapine has been associated with weight gain, at times substantial, as well as disturbances in glucose and lipid metabolism.7 The addition of samidorphan, an opioid antagonist, to olanzapine in a single tablet may act to decrease the amount of long-term weight gain that can be expected for some patients taking olanzapine alone, consequently minimizing the anticipated increase in waist circumference (a proxy for the measurement of burden imposed by metabolically active adipose tissue). Approval of OSC for the treatment of schizophrenia was based on 2 pivotal randomized controlled trials and their extension studies.8-11 Approval of OSC for bipolar I disorder (acute treatment of manic/mixed episodes as a monotherapy or adjunctive to lithium or valproate, and as a monotherapy maintenance treatment) was based on legacy studies conducted with olanzapine, after establishing that samidorphan does not alter the pharmacokinetics of olanzapine, including in combination with lithium or valproate.3,12,13 OSC should be distinguished from a different combination product, olanzapine-fluoxetine combination (Symbyax, originally manufactured and distributed by Eli Lilly and Company/Lilly USA, LLC, Indianapolis, IN USA), approved for acute depressive episodes associated with bipolar I disorder and for treatment-resistant depression.14

OSC offers the potential to consider olanzapine earlier in the treatment of schizophrenia or bipolar I disorder, especially among practitioners who might otherwise be hesitant to prescribe this agent because of concerns over the risk of excessive weight gain.

OSC is available in 4 dosage strengths containing 5 mg, 10 mg, 15 mg, or 20 mg of olanzapine; all tablets contain 10 mg of samidorphan.2 The recommended starting dose for OSC mirrors the language contained in the legacy olanzapine product label.4 For schizophrenia, the recommended initial dose (olanzapine/samidorphan) is 5 mg/10 mg or 10 mg/10 mg once daily. For bipolar I manic or mixed episodes, the recommended starting dose for monotherapy is 10 mg/10 mg or 15 mg/10 mg, and for use with lithium or valproate, 10 mg/10 mg. For all indications, the recommended target dose can be 10 mg/10 mg, 15 mg/10 mg, or 20 mg/10 mg, with 5 mg/10 mg as an additional potential dose for maintenance monotherapy of bipolar I disorder. The maximum dose is 20 mg/10 mg once daily. Because the amount of samidorphan in each tablet is fixed at 10 mg, combining tablets of OSC, or cutting OSC tablets in half, is not advisable.

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