bupropion + lithium + mirtazapine + thyroid hormone

This is a combination regimen consisting of four agents commonly used in the management of treatment-resistant depression (TRD): bupropion, lithium, mirtazapine, and thyroid hormone. - **Bupropion** is a norepinephrine-dopamine reuptake inhibitor (NDRI) antidepressant that increases synaptic concentrations of norepinephrine and dopamine by inhibiting their reuptake. - **Lithium** is a mood stabilizer with multiple mechanisms including modulation of neurotransmitter release and second messenger systems; it is often used as an augmentation agent in depression. - **Mirtazapine** acts as an antagonist at central presynaptic α2-adrenergic inhibitory autoreceptors and heteroreceptors, increasing noradrenergic and serotonergic transmission; it also antagonizes 5-HT2 and 5-HT3 receptors. - **Thyroid hormone** (typically triiodothyronine/T3 or levothyroxine/T4) augments antidepressant response through modulation of gene expression affecting neurotransmitter systems involved in mood regulation. This combination targets multiple neurochemical pathways to maximize antidepressant efficacy for patients who have not responded to standard monotherapy or dual therapy approaches[3][4][6]. The use of such multi-drug regimens reflects clinical strategies for complex or refractory cases but carries increased risk for drug interactions and adverse effects.