I can think of a hundred other drugs but they're either analogues of a parent compound, which means they're not really unique enough to differentiate, or are substances that few have ever heard of. 13 pages is a good run, but there's not much more to cover unless we move on to non recreational substances, hormones, steroids, RC's (which again are typically too similar to differentiate), or repeat previously mentioned drugs. I'm sure some have escaped the wrath of the riddle, but it's becoming a chore finding one that many have heard of. What good is a riddle if nobody will ever know the answer?