You shouldn't be doing drugs and yes, they do slow down your heart rate.
Some drugs are depressants which means that they slow down our reactions.
They can slow down your central nervous system (Brain)
Depressants
Depressants slow everything down. They affect the central nervous system and "depress it."
Alcohol and marijuana are two drugs that slow a persons reactions, alcohol can also slow down the body's functions and can shut down a persons liver. Almost all other drugs are stimulants that can speed a persons heart rate and brain activity.
BRAIN! They slow down the chemical firing rate in your brain i believe. =]
It lowers the blood pressure, and lowers the heart rate for starters.
they stop the signals travelling down the nerves by blokcing the synapses
Drinking alcohol temporarily slows the rate of respiration.
nurofen
Suppressants speed your system up, while depressants slow you down.