Alright, I know we should all suspend our disbelief and all that, but uh…
If you are going to go out of your way to actually name the drug being used, please do a little research and make sure the drug in question actually does what you claim. Cocaine? Not a sedative. Yes, it was used historically for pain killing and soothing tonics. It is still not a sedative.
Chloroform? Very dangerous and doesn’t work at all like it’s advertised on TV. For starters, the average person can hold their breath for at least thirty seconds, so a chemical that has to be breathed in is not your best choice for knocking someone out fast. I hate to break this to you, but there is no wonder drug that will knock people out fast that doesn’t have to be very carefully calibrated to an individual. That’s why anesthesiologists get paid large amounts of money.
Some artistic license can be forgiven. I’ve done the bash over the head with no long term consequences thing a few times in my stories. In real life, the amount of force needed to knock somebody out and the amount needed to kill them overlap considerably, to the point its almost random chance that decides which one is going to occur.
Chemical restraints to exist (we’ve all heard of roofies) but they aren’t instant things and they can and will make a person very ill. They can also kill, particularly if a person is already on medication. At best, they still take about three minutes to work and can take much longer. You will also occasionally find people upon whom they don’t work at all or they have a counter effect. Benadryl is commonly given as a mild sedative, yet on some people it actually works as a stimulant. That could even make for a good story twist for you – your professional kidnapper/assassin doses someone, only to end up with a hyperactive squirrel rather than a compliant sloth.