I would imagine it is an antiquated term for medications that would be on the counter as opposed to those a pharmacist would have to get from behind it. That's just speculation of course, and anyone is welcome to correct me, but that's basically what some terms boil down to -- they stemmed from things in olden times, and as things changed they began losing their original meaning, but due to the phrases still seeing widespread use, they stuck around.
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Your neurodiverse (Aspie) score: 91 of 200
Your neurotypical (non-autistic) score: 107 of 200
You seem to have both neurodiverse and neurotypical traits