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.
Which, ironically, is the actual reason Kinder Surprise are illegal in the US: It’s not a specific ban, it’s that you’re not allowed to put non food inside of food. Which is prima facie completely reasonable.