A 36-year-old woman has been brought into the Emergency Department (ED) having seizures that have lasted for 35 minutes before her arrival. On arrival, she is continuing to have a tonic-clonic seizure. She is a known epileptic and is currently taking lamotrigine for seizure prevention. She has had a single dose of rectal diazepam by the paramedics on route approximately 10 minutes ago. On arrival in the ED, intravenous access is gained, and a dose of IV lorazepam is administered. After a further 10 minutes, a phenytoin infusion is commenced. A further 20 minutes have passed, and she has failed to respond to your above treatment.