of course you are able to.. maybe you mean should i?
well from a health point of view, probably best not too the combining of e with a depressant (like alcohol) is generally considered a no no... it will definitly dehydrate you faster, and the e will be dehydrating you enuf already... so your comedown wil be worse, and combined with a hangover too... also the amphetamine will mask the amount of alcohol you have drunk, so yo may be putting a lot more stress on your liver/kidneys than you realise.
from a general enjoying your roll point of view, probably not either, it will dull the euphoric feeling, and why would you want that?
most people i know cant stand to be around alcohol while rolling. and especially not around drunk people, there is nothing worse than trying to deal with drunk people while eing or tripping. it is just awful....
just stick to water is my advice, you'll hopefully be having enuf fun you wont want to drink.
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.... he who makes a beast of himself, rids himself of the pain of being a man...