These include: • valproate, used to treat epilepsy and mental health problems • carbamazepine, used to treat epilepsy and mental health problems • phenytoin, primidone or phenobarbitone, used to treat epilepsy • olanzapine, used to treat mental health problems • risperidone, used to treat mental health problems • rifampicin, which is an antibiotic • a combination of lopinavir and ritonavir, used to treat Human Immunodeficiency Virus (HIV) infection • hormonal contraceptives, such as the Pill (see below).