Competitive inhibitors increase the Km of the substrate. The Km represents how easily a substrate can bind the active site, with a lower Km representing easy binding, and a higher Km meaning more difficult. If you add a competitive inhibitor, like ethanol in this case, it makes it more difficult for the methanol to bind the active site, because it must compete with the ethanol.

lolol so instead of using fomepizole they just gonna get him real drunk

I hate these so much these questions give me MCAT PTSD

The Km is inversely related to the affinity of the enzyme for its substrate so in this case we want to increase Km so that the affinity of hepatic alcohol dehydrogenase decreases for methanol and the ethanol can then act as a competitive inhibitor by overcoming the concentration of methanol thus preventing toxicity.

I feel like everyone is talking about all these reactions when I just draw out the graph. We wanted to increase the Km (move it on the X axis), that would lead to it crossing on the y axis (Vmax). if we kept the Km at the same spot, it wouldn't overlap the point on the max else they'd have been the exact same lines...

Correct me if I'm wrong, but I think the reason ethanol is used to competitively inhibit alcohol dehydrogenase is because its' metabolite (acetaldehyde) is much less toxic than formaldehyde (what methanol is catabolized to).

So you better have a "bad situation" than a "worse situation".

This would be, of course, in case fomepizole is not available and in accordance to the guidelines.