Interaction between tramadol (TRAMAL, generics) and lamotrigine (LAMICTAL, generics): A 70-year-old patient with epilepsy, after decades of pharmacotherapy, has histologically confirmed antiepileptic drug-induced osteomalacia with pronounced skeletal deformation and an abnormal fracture tendency. The convulsive disorder, which has existed since childhood, is satisfactorily stable on lamotrigine (LAMICTAL, generics), valproate (CONVULEX, generics) and two other antiepileptic drugs. Following an elbow fracture, in hospital he received tramadol (TRAMAL, generics) plus dipyrone (NOVALGIN, generics) for pain relief, while his antiepileptic medication was maintained. 24 hours after the start of this co-medication, he presented nystagmus, double vision, severe ataxia, syllabic speech, drowsiness and nausea. The attending physicians initially interpreted the symptoms as central nervous effects of the opioid and discontinued tramadol, but at the same time arranged for the levels of the administered antiepileptic drugs to be measured. When the laboratory results were received and showed an extremely elevated lamotrigine level of 21.5 µg/ml (therapeutic range: 1.5-4 µg/ml), the neuropsychiatric symptoms had already subsided completely (NETZWERK Report 15.301). Lamotrigine is eliminated with the aid of UDP-glucuronyltransferases (UGT). If these are inhibited, for example by valproate, the half-life is considerably lengthened. The usual lamotrigine dose should therefore be reduced during co-medication with valproate (GlaxoSmithKline: LAMICTAL Summary of Product Characteristics (SPC), as at Sept. 2008). Tramadol is also eliminated with the aid of glucuronic acid conjugates (Grünenthal: TRAMAL SPC, as at July 2008). In the patient concerned, elimination of lamotrigine may already have been reduced by valproate and further inhibited by the additional administration of tramadol - resulting in an excessive lamotrigine level (Drug Commission of the German Medical Association: letter of 2 April 2009). As epilepsy patients are particularly at risk of injuring themselves, then possibly requiring analgesics, the possible interaction with tramadol seems relevant to us.