Publication:

Paradoxical nocturnal agitation associated with mirtazapine therapy

This report describes an 85 year old woman presenting with a mixed delirium with risk factors of hyponatraemia, polypharmacy, and bilateral frontal lobe atrophy with small vessel cerebrovascular disease. Treatment for depression with oral citalopram had been revised to oral mirtazapine, with the aim of reducing the risks of recurrent hyponatraemia noted with the former. She developed an evolving adverse drug reaction (ADR) symptom profile of insomnia, and later severe paradoxical nocturnal agitation. These symptoms were subsequently noted to correlate with both the night-time dosing pattern, and the increased dosing regimen of the mirtazapine. The symptoms settled rapidly following withdrawal of the mirtazapine. The report briefly reviews the relevant literature, and two previously validated causality assessment systems are applied to the index case to support the pharmacovigilance process. This is aimed at promoting objectivity in assessing for the likelihood that the suspected medication (mirtazapine) was the cause for the noted adverse drug reaction.