Changes in medication associated with epilepsy‐related hospitalisation: a case‐crossover study

SUMMARY Aim To assess the association between changes in medication and epilepsy-related hospitalisation.Methods Data were obtained from the PHARMO Record Linkage System (Jan 1998 to Dec 2002). We conducted a case-crossoverstudyamongpatientswithafirstep ilepsy-relatedhospitaladmissionwhohad continuouslyusedatleastoneantiepilepticdrug (AED) during a 28-week period before admission. For eac h patient, changes in medication in a 28-day window beforehospitalisation were compared with changes in four earlier 28-da y windows. Evaluated changes were: changes in AEDs (patternand dosage), changes in interacting co-medication and change s in non-interacting co-medication (i.e. introduction of non-interacting drugs). The strength of the association between ch anges in medication and epilepsy-related hospitalisation wasestimated using conditional logistic regression analysis and e xpressed as odds ratios (ORs) with 95% confidence intervals (CI).Results Out of 1185patientswith a first epilepsy- related hospitalisation, 217 patientsmet the inclusioncriteria. Of the changesinantiepileptictherapy,discontinuationshowedatrendtowardsanincreasedrisk ofhospitalisation(OR:2.57;95%CI:0.81–8.17).Drug interactions influencing antiepileptic therapy rarely occurred. Introduction of three or more non-interacting drugs wassignificantly associated with epilepsy-related hospitalisation (OR: 4.80; 95%CI: 2.12–10.87). Of individual drugs, addition ofantimicrobial agents was significantly associated with epilep sy-related hospitalisation (OR: 1.99; 95%CI: 1.06–3.75).Conclusions ChangesinAEDtherapywerenotsignificantlyassociatedwithepilepsy-relatedhospitalisationandfewdruginteractionsinfluencingantiepileptictherapyoccurred.However,patientsstartingthreeormorenewnon-AEDshadanearlyfive times increased risk of epilepsy-related hospital admission. Copyright # 2006 John Wiley & Sons, Ltd.key words—epilepsy; antiepileptic drugs; hospital admission; drug interaction; case-crossover studyReceived 6 December 2005; Revised 22 August 2006; Accepted 2 September 2006