mirzatapine

my mother in law is treated with mirtazapine (rhemeron) + lithium. she started to take 45 mg mirtazapine a day and lithium a month ago. she complains on fatigue, saying that her legs feel heavy and stiff, that her movements are clumsier, and she feels like having a mist in her head. We would like to know whether these are known side effects of her medicine, and especially if and when they are likely to disappear.

i am also taking this medicine - remeron. and the side effects that you remind are very familiar and they tend to go away or the patient gets used to it.