Can my meds be prescribed in Japan?

My husband and I intend to move to Japan within the next year or two (location tbd, it would depend on jobs). One of the biggest concerns I have before we even start the process is my daily medications. Does anyone know if the below can be prescribed by a Japanese doctor? Google is not giving the best answers.

Valtrex 500mg daily, not "as needed"

Lamotrigine ER 300mg. It looks that dosage is too high, so I would taper off to a lower one beforehand. And apparently they don't offer the ER version?

by Art-by-B2R