“Alcohol is a mild poison” has been a house rule within my extended roleplaying circles for a long time. It fits well into almost any setting or metaphysics, and allows you to do interesting things with intoxication.
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Hmmm. It's often said that the difference between medicine and poison is a matter of dosage.
Which means that you could potentially use lesser restoration to kill someone who is receiving mundane treatments for a lethal disease.
Or, heck, consumed in sufficiently large doses, even water can be toxic.
That relationship is why in every edition but fifth, healing is necromancy, and why Heal and Harm are identical in 3rd/pf, because they're the same fundamentally, you just had to tweak the settings on one to get the other.