My at a glance emergency list:
Naloxone (especially helpful in case of fentanyl–or any opiate–overdose)
Any kind of depressant
Cocaine info, via Drugs.com
Although drugs.com seems to go a modern route when it comes to treatments (which is okay if that is what you are looking for!), I have found drugs.com to be a very great resource for learning about a drug and it’s symptoms and side effects.
Or, Cocaine info via Recovery.org
Learn about causes, withdrawal, recovery.
Fentanyl is a synthetic opioid and is up to 100 times stronger than other opioids like morphine, heroin or oxycodone. It is a narcotic analgesic. (drugs.com)
Naloxone is used to reverse an opioid overdose and help restore breathing by blocking or reversing the opioid effects.
Learn how to use Naloxone before it is needed.