Samidorphan L-malate is the salt form of samidorphan, an opioid antagonist used in combination with the antipsychotic olanzapine to treat schizophrenia and bipolar I disorder, reducing olanzapine's typical weight gain side effect by blocking opioid receptors. It's a fixed-dose combination drug, an atypical antipsychotic with opioid-blocking properties that helps manage symptoms while mitigating metabolic issues, but carries risks like opioid withdrawal if opioids are used concurrently.