[Chronic dizziness in a pain patient--pharmacogenomic identification of tramadol as cause].

This casuistic reports on a 59-year-old pain patient taking normal dosage Tramadol as analgetic drug, who suffered from chronic dizziness leading to immobilisation for more than 9 months. On admission to inpatient rehabilitation Tramadol was removed in exchange for morphine sulphate with the unexpected result of a prompt and lasting stop of dizziness. A molecular-genetic investigation showed a duplication in the CYP2D6 gene. This genetic situation caused a quick metabolizing-status for substances dependent on CYP2D6 like Tramadol, which is a prodrug. The quick metabolizing-status resulted in an increased rate of active Tramadol-metabolites which caused the chronic dizziness. Under morphine sulphate which is metabolized independently of CYP2D6, a sufficient analgetic outcome could be achieved. Dizziness did not appear in the patient any longer, and he could be mobilised during rehabilitation. Pharmacogenomic knowledge has helped develop a sustainable concept for rehabilitation of this seriously ill patient, and to put it into practise successfully.