Has Catholic excommunication ever caused the dethronement of any king?
Wikipedia has a list of people excommunicated by the Catholic Church, with a little explanation of the causes for each case, but (understandably) none of the effects.
I'm curious if this measure has caused the downfall of any ruler, specially in the Middle Ages, when the power and influence of the Catholic Church was most strong.
No king has ever been dethroned as a result of being excommunicated. This mostly due to them being powerful enough militarily and politically in order to deter rival claimants from being able to seize the throne from them. As a result excommunication served more to delegitimize a king's right to rule than to summarily end it. The closest to an actual dethronement was when Holy Roman Emperor Henry IV was compelled to seek absolution for his excommunication from the Pope in 1077. However this wasn't in order to regain his throne as it was to try to regain legitimacy which would help his cause as he was trying to put down several rebellions by rival claimants to the imperial throne.