There are a ton of interacting mechanics in this game with different effects which I don't feel have been fully explored. Specifically there are some non standard verbs that have been ignored. Like throwing, or changing your intent. The game as it is doesn't feel incomplete at all because it lacks some of these effects, but I feel they could add an extra dimension to some interactions.
Psychotics
Euphoria: you can't change your intent from helpful, messages about how good everything feels, possible hallucinations, possible collapsing to "feel how nice the floor is", possible forced speech about how great it is or how high you are, hugging everyone.
Enraged: You can't change your intent from harmful, messages show up detailing how your face is feeling red or how angry you are, you occasionally yell, shake angrily, clench your fists, or throw items in your hands.
Harmful effects
Muscle relaxant: Slight difficulty speaking with letters being deleted from your text, unable to take any intent but grab and helpful, cannot run, possibility of falling over and collapsing, possibility of dropping items in your hands. At amounts over the overdose point or as a symptom of disease progression possible incontinence, paralysis, or potentially the inability to breath until the chemical concentration drops lower.
Blood thinners: Wounds bleed more often, could be added as a disease symptom or a side effect added to some of the chems that are already available making them very slightly more situational.
Organ specific damage: Right now most overdoses just give tox damage, I think it might be interesting if instead they damaged the kidneys, lungs, liver, or heart specifically.
Sensitivity: Overdoses happen far more quickly, and even a small amount of alcohol will get you drunk. Probably something to be careful with implementing since there are some bad doctors in medbay.
Blindness: Simple effect, but nothing seems to inflict it but massive eye damage and genetic mutation, blindness toxins or just heavy metal toxicity sounds like it could be interesting.
Immunocompromised: all injuries have a high chance to get infected and there is a chance for spontaneous infection of the organs. (Possibly makes some viral effects less pronounced.)