Considering that the frequent occurrence of cluster seizures and a high seizure density seems to be linked to a poor drug responsiveness in canine epilepsy patients and upregulation of p-glycoprotein and that cluster seizures have a major impact on quality-of-life in epilepsy patients, we separately assessed an effect on occurrence of cluster seizures defined as days with cluster seizures. This evidence concerns the gene ABCB1 and epilepsy.