Samidorphan, which was developed by Alkermes, is an opioid receptor antagonist that has been co-formulated with olanzapine into a single-dose oral tablet to mitigate the risk of weight gain while providing the therapeutic effect of olanzapine. In June 2021, the Food and Drug Administration (FDA) approved Lybalvi (olanzapine/samidorphan) for indications including treatment of adults with schizophrenia and/or bipolar I disorder (acute manic episodes or acute episodes with mixed features).