As the comment above you alluded to, and as it's been evidenced many times, it is not enough to affect change. These aren't "side effects", the poorest feel the main effect of the sanctions.
They're side effects, but not entirely unintended.
If the head of that state (and party elites etc) don't meet the requests of the sanctioning states, the ensuing poverty can mobilize the impoverished masses. This can backfire and drive them to further nationalism/jingoism, but it opens a window of opportunity for the opposition (and, more cynically, covert agents and external forces).
If the head of that state (and party elites etc) don't meet the requests of the sanctioning states, the ensuing poverty can mobilize the impoverished masses. This can backfire and drive them to further nationalism/jingoism, but it opens a window of opportunity for the opposition (and, more cynically, covert agents and external forces).