Require higher stimulant doses while on memantine

Been using memantine as a mood stabilizer and tolerance prevention adjunct to my vyvanse prescription for ADD. I noticed I need a much higher dose of vyvanse to achieve the same effects as I had without memantine. Does this make sense to anyone? Seems like the opposite of what I was supposed to expect. Definitely smooths out the Ups and downs but the higher dose thing is slightly worrying. Maybe it’s the D2 agonism? Also worth noting I have decreased DRD2 receptor density according to my genetic results.