Japandwell
Narcotics and neurotoxin are different drugs. Your posts are confusing me.
Far more worrying is the slit lamp discussion. Regardless of whether there is a slit lamp examination or not, lying to obtain a medical or failing to disclose is a serious offence - called offense in the USA. As a pilot you must be aware of this so surely your advice to your 'student' must be to own up. What on earth is an educated decision???????
Depending on the relationship between you and the student it might also lay you open to criminal prosecution. I know nothing of US law in this respect but our experience of what the Feds do to British citizens who commit offences even if not in the USA suggests you might be incarcerated in the middle of the Arizona desert for 200 years