Basic Trope: A character is portrayed as living a functional life despite his/her addiction to drugs.
Straight: Bob is addicted to drugs, but manages to function well socially, hold down a steady job, and hide his addiction from most of his friends.
Exaggerated: Bob's life as a married man with three kids, his career as a surgeon, his sideline as an exercise coach, his holiday hobby of exploring jungles, and his physical health in general are all completely unaffected by the fact that he's addicted to several varieties of hard drug, including heroin, crack cocaine and ecstasy.
Downplayed: Bob is almost always seen with a beer in his hand when he's at home, but never appears inebriated, and nobody comments on it.
Justified: Bob has severe chronic pain and the drugs he took ends up building up such a dependence that he'd have trouble kicking the habit if he somehow lost all the chronic pain. He is determined to live as he did before the accident.
Bob is a drug addict, and as a result his life has completely fallen apart - he can't hold down a job, he lives in a slum, his wife has left him, his kids hate him, and his health is rapidly deteriorating.
Bob has recently stopped taking drugs, but this results in the majority of his friends leaving him because they consider him no fun when he isn't on drugs, his boss firing him for not working all night due to being extremely hyped up from the drug, and being in debt to the rehab clinic.
Subverted: It turns out that Bob has never taken drugs and was only pretending to be a Functional Addict to impress his friends; after he starts taking drugs for real, things go downhill as he loses his job, his wife divorces him, he goes bankrupt, and his health starts to deteriorate.
Double Subverted: ...but then it turns out that Bob was fired due to a long record of poor performance, his wife was planning to divorce him long before he started drugs, his financial trouble is due to accumulated gambling debts, and his deteriorating health is due to a Soap Opera Disease he hasn't told anyone about. Drugs become one of the few things that aren't actively wrecking his life.
Parodied: Bob is so convinced that drug addiction is completely inconsequential that he celebrates Christmas by dumping crack cocaine in the water main.
Zig Zagged: How Bob deals with drugs is incredible inconsistent. In some episodes he's a complete wreck. In other ones he's about as good as everyone else including being sober. In other ones he's more functional than everyone else. However it is later revealed that he wasn't on drugs on the earlier episodes just dealing with mental health issues. He later did start taking drugs to self medicate however.
Averted: Bob is addicted to drugs, and while it isn't necessarily a major part of the story or even his character, he does suffer from most of the issues that tend to be associated with it - health issues, financial trouble and general instability in his life.
Enforced: The overall story makes Bob's status as a Functional Addict seem somewhat implausible and/or irrelevant, but the author is a hardline activist for the legalisation of narcotics and shoehorns it in anyway.
Lampshaded: "Boy, Bob seems pretty normal for a bloke who's been hooked on the pill for that long, doesn't he? Not like on TV at all."
Invoked: Facing a difficult time in his life, Bob starts taking drugs because he's done years of research on narcotics and is certain that he's the sort of person who will function relatively well even if he does become addicted.
Defied: The Aggressive Drug Dealer picks out Bob as a victim specifically because he knows that Bob's life is in a shambles and his mental state is already shaky, and thus he's unlikely to become this kind of addict.
Discussed: "Bob, shouldn't you talk to someone about this pill-popping thing? I know you seem pretty normal now, but stuff like this never ends well on TV."
Conversed: Alice and Bob watch a TV show in which a character is portrayed as mostly functional despite his drug addiction; they then get into an argument about whether this is plausible.
Deconstructed: Bob, a Functional Addict, gives a lecture at a high school explaining that drugs can be very dangerous, that his own situation certainly doesn't mean everyone who becomes an addict will be functional, and that the drugs he takes could still have a negative effect on his life.
Reconstructed: ...but also elaborates on his own current lifestyle as a Functional Addict and explains how it IS medically plausible.