I just wanna say this should be edited from the OP, quoted:
You mean pharmaceuticals help cure and relieve people all around the world. From my knowledge, cocaine, heroin, and other various lethal substances do not have any valid positive effects on the human brain or body. Marijuana is the only researched narcotic that has some positive effects, and I'd say is one of the least harmful depending on how it is used. Pharmaceuticals and general narcotics should be differentiated.
Drugs and pharmaceuticals are synonyms. But let's see..
Cocaine is Schedule II in the US. That means that it has medically accepted use but it has a high potential for abuse.
Heroin itself is Schedule I, but that doesn't mean it has no medical use at all. It's very well known that heroin is a really really powerful painkiller. It's just that better ones exist to prescribe to people.
"Various lethal substances" can mean anything, but here's some things I consider 'lethal substances.' Methamphetamine is commonly prescribed as ADHD medicine under the brand name Desoxyn. Oxycodone is just as powerful and addictive as heroin, commonly prescribed for pain treatment under the brand name Oxycontin. loving Tylenol, which is OTC, causes countless hospital visits because of the relatively small therapeutic window (that's the term you were looking for).
However, that's only what the government recognizes. On the topic of magic mushrooms as a medicinal treatment for cluster headaches (nicknamed 'Self Delete headaches' because they are widely believed to be the most painful experience a human being can have), Harvard Medical School released a study that noticed that "Twenty-two of 26 psilocybin users reported that psilocybin aborted attacks; 25 of 48 psilocybin users and 7 of 8 LSD users reported cluster period termination; 18 of 19 psilocybin users and 4 of 5 LSD users reported remission period extension."
[1] So this means that 22/26 people were able to stop the attack after it started, 25/48 were able to stop chains of them, and 18/19 experienced longer breaks between episodes. The LSD sample size was lower, but still 7/8 and 4/5 are huge numbers. Neither LSD nor magic mushrooms have accepted medical use in the US.