Used primarily in the treatment of major depressive disorder, (R)-Mirtazapine acts as a noradrenergic and specific serotonergic antidepressant. It enhances central noradrenergic and serotonergic activity by blocking presynaptic alpha-2 adrenergic receptors. Its strong antagonism of postsynaptic 5-HT2 and 5-HT3 receptors contributes to improved mood, reduced anxiety, and fewer gastrointestinal side effects compared to other antidepressants. It is also prescribed off-label for insomnia, appetite stimulation, and nausea control, particularly in palliative care settings. Due to its sedative properties, it is often administered at bedtime. The (R)-enantiomer is responsible for most of the pharmacological activity, making it a key component in achieving therapeutic effects with lower dosing and potentially fewer side effects.