A main character is a well documented drug and alcohol addict, slow hints in episodes leading up before full relapse. Drugs are shown widely in packets (Oxy), drugs are shown being taken, snorted, smoked and implied injection. Character is also shown high on many occasions. Very tactfully done though and not over the top.
Another main character is a documented drug user who had not used in years. Shows flashbacks to her drug use and why she is so sensitive about them now.
Drinking is common in bar scenes.
A character's ex-wife was a drug addict.
A main character is alcoholic.