Posterior Reversible Encephalopathy Syndrome Induced by Mirtazapine Overdose: A Case Report

Introduction: Posterior reversible encephalopathy syndrome (PRES) is a neurological emergency typically associated with hypertension or drug toxicity. Although mirtazapine is not a classical serotonergic agent, overdose may induce serotonin syndrome, which can contribute to PRES. Case Presentation: A 50-year-old woman presented with seizures, impaired consciousness, and autonomic instability following ingestion of > 300 mg mirtazapine. Magnetic resonance image (MRI) revealed vasogenic edema in the parieto-occipital and frontal lobes. Her clinical features fulfilled the Hunter criteria for serotonin syndrome. Treatment with cyproheptadine led to full clinical and radiological recovery. Discussion: Serotonin syndrome may disrupt cerebral autoregulation and impair endothelial integrity, contributing to PRES. Although rare, similar cases have been reported with other serotonergic agents. This is the first reported case of mirtazapine overdose resulting in serotonin syndrome-associated PRES. Conclusion: Clinicians should recognize that mirtazapine overdose can cause serotonin syndrome and secondary PRES. Early identification and serotonin antagonism are crucial for recovery and prevention of sequelae.