Other kinds of narcotic or hallucinogenic drugs increase your senses, which makes it easier for you to travel in other worlds. They work as a shortcut, but since you don't know how to handle those drugs you are on a dangerous journey. If you search for spirituality with drugs in your body, your protection is low. If you should meet immature spirits you don't know how to handle them, and it could get very uncomfortable for you. Don't take the chance.
Skilled shamans know how to protect themselves and how to handle unwanted spirit beings.
Without drugs, the road to other worlds could seem to be longer, but the detour is worth to make since you're keeping your control and the ability to protect yourself. You can reach the same experience without drugs as you can with drugs, but it requires practice. Skill always requires practice, no matter what you're trying to achieve. The risks in reaching other worlds with the help of drugs are too big. You may get to pay a price that is far too high.