Giving an excuse to someone offering drugs is the only way to refuse them.

False.  You need to be assertive and tell them the answer is no.  You must be clear in your stance in refusing these things.  Making excuses is like hiding and shows weakness. When they see that, they will not stop and will keep harassing you unless you make it clear that you don’t want it.

the answer is solomon northrup. he was a free-born african american, abolitionist and professional violinist that was drugged, kidnapped and sold as slave in 1841 and remained in captivity until 1853 where he regained his freedom with the of the then-governor of new york, washington hunt. he wrote and published his memoirs "twelve years a slave" in 1853, and in this text, he tells the story of his escape thru one of louisiana's swamps (the great pacoudrie swamp) in which he ended up covered in green slime from crossing the surface of the dead water.