This includes opiates which are pain killers and other drugs such as sedatives. It is important to remember that classification of drugs is not as clear cut as it may sound. The way a drug affects an individual is not simply down to the chemical itself. The effects depends on how the drug is taken, the dose, your mood at the time, who you are with, where you are, your expectations of what the drug will do, what you have eaten that day, etc. This results in the effects often being very unpredictable.
Drugs work in different ways.
Psychoactive drugs contain chemicals which alter the function of the brain. The chemicals in the drug are taken to the brain through the bloodstream which is why they effects differ for different methods of taking the drugs. They get into the bloodstream by injecting, smoking, sniffing, or swallowing the drug. It is important to remember that the street names for drugs vary from one area to another. It is also difficult to know the real identity and purity of a drug when it is purchased ilegally.