mebendezol

Never heard of it so probably not a great recreational drug. Oooh Wikipedia confirms

Mebendazole is a highly effective, broad-spectrum antihelmintic indicated for the treatment of nematode infestations

Mebendazole sometimes causes diarrhea, abdominal pain, and elevated liver enzymes. In rare cases, it has been associated with a dangerously low white blood cell count, low platelet count, and hair loss,[14][15] with a risk of agranulocytosis in rare cases.