Synonyms for Exhausting (same or very similar meaning)
WordNet sense 1 (having a debilitating effect):
drainingWordNet sense 2 (impairing the strength and vitality):
debilitatingWordNet sense 3 (producing exhaustion):
tiring, wearing, wearyingWordNet sense 4 (requiring great physical effort):
effortfulFrom the ODE community, based on WordNetadd/edit