Ketamine + Mirtazapine together

Ketamine + Mirtazapine:

1. Neurochemical interactions: Ketamine blocks NMDA glutamate receptors and also has an affinity for opioid receptors and an effect on monoamines. Mirtazapine blocks 5-HT₂A/₂C and 5-HT₃ and increases norepinephrine via α₂ blockade. Mirtazapine has no direct action on NMDA or GABA; the agents act partly on different systems. Due to 5-HT₂A and 5-HT₃ blockade, mirtazapine may possibly reduce some emotional side effects of ketamine (e.g., nausea).

2. Therapeutic effect: In a clinical setting, ketamine is often combined with antidepressants. The combination with mirtazapine is considered relatively safe, and it is sometimes suggested that it may support the antidepressant response (for example, through mirtazapine's noradrenergic boost). Ketamine can complement the action of mirtazapine with rapid mood improvement. However, the powerful sedative effects of mirtazapine can influence the subjective ketamine experience. Low doses of ketamine alongside mirtazapine can enhance overall sedation, which in some cases can disrupt the therapeutic setting (e.g., reduced emotional sharpness). Nevertheless, patients undergoing ketamine therapy are often advised to continue their medication, as the combination is generally well tolerated.

3. Danger or risks: The main risk is severe sedation and cognitive impairment. Mirtazapine causes drowsiness (especially at the start), and ketamine induces a dissociative feeling. Together, at high doses, they can lead to severe drowsiness, dizziness, and (in exceptional cases) respiratory depression. This risk is higher in the elderly or frail. Additionally, hypotension may occur because both agents slightly lower blood pressure. Serotonin syndrome is unlikely (ketamine causes minimal serotonergic stimulation). In general, there is no indication of increased organotoxicity, and clinical studies show no serious interaction, provided dosage is cautious. Outside of clinical settings, the combination is not recommended.