Tachyphylaxis to the Sedative Action of Mirtazapine

Patient: Female, 30 Final Diagnosis: Depression Symptoms: — Medication: Mirtazapine Clinical Procedure: — Specialty: Psychiatry OBJECTIVE: Unusual or unexpected effect of treatment BACKGROUND: The pharmacological term tachyphylaxis is used to describe rapidly occurring response desensitization, a situation where the biological response to a given drug dose diminishes when it is given continuously. This pharmacological phenomenon is well observed in some drug categories such as ephedrine, nitrates, beta blockers and H(2) antagonists. Mirtazapine is a widely-used antidepressant with a multimodal mechanism of action. CASE REPORT: In the present case, we report rapid onset and consistent tachyphylaxis regarding the sedative action of mirtazapine in a 30-year-old female. CONCLUSIONS: To our knowledge this is the first reported case of rapid onset and consistent tachyphylaxis to the sedative effect of mirtazapine confirming the complexity of the pharmacological profile of the drug.