Apparently most rashes associated with this drug occur within 2 - 8 weeks after starting it.
(note these rashes may be life-threatening: stevens-johnson-syndrome/toxic epidermal necrolysis and drug reaction
with eosinophilia and systemic symptoms (dress)). One source states that stopping the drug at any point & restarting at the same dose can trigger a rash
. So, it's possible, even after a year.