OBJECTIVE: In the framework of a case report on a patient suffering from major depression and inflammatory bowel disease we address the pharmacotherapeutical options in case of subtherapeutic mirtazapine levels. METHODS: We applied therapeutic drug monitoring (TDM) and cytochrome P450 2D6 genotyping, and switched to an orodispersible tablet. RESULTS AND CONCLUSION: Thus, mirtazapine plasma levels could be raised and clinical improvement of the depressive symptoms was achieved.