The U.S. government paid TV networks to make sure that anyone using drugs was portrayed as a loser. ER, Beverly Hills 90210, Chicago Hope, The Drew Carey Show, 7th Heaven and other shows had their scripts reviewed by the government and changes made so the network could pocket some cash.
This started with the Nixon Admin. in the 1960s, as related by Harlan Ellison among others.
8 Simple Rules: In one episode, Kerry is found with marijuana in her backpack. CJ seems to accept it, but the rest of the cast reacts with great shock, especially her boyfriend and mother. Cate even gives a moving lecture about it. It should be noted that Kerry was only holding the pot for someone else at school and she wasn't actually planning on smoking it herself.
Dr. Franklin becomes addicted to stimulants in Season Three. He's been using them to improve his concentration. Too much tends to have the opposite effect, though. Another doctor lost her license due to the same problem, as seen in Season One's "The Quality of Mercy".
Garibaldi's alcoholism as well. Both are arguably handled well.
For a time, Franklin was on a self-induced detox, going on Walkabout in the station's back alleys so he could work out his problems without entangling his friends. Along the way he meets a singer in a club who he thinks is hooked on a narcotic called Medezine. She is suffering from a cripplingly painful, incurable disease, and the medezine is used to treat the pain.
Breaking Bad: Played straight, and how. Goes into the violence and crime, the desperation, and the screwed up lives of meth addicts. Coke will fuck you up. Heroin will kill you. Even alcohol will make you chuck up your guts if you take a couple of shots when underage. Pot, surprisingly, gets off pretty lightly aside from the (arguably Felony Misdemeanor) reactions of Walt's family. Although it certainly does come out as anti-drugs, Breaking Bad is quite even-handed. The show makes arguments for drugs as a personal choice and portrays a variety of characters (among them Jesse) as high functioning meth addicts. The show is much more critical of the criminal industry surrounding drugs than of the substances themselves (except heroin, which ironically does not get off lightly).
Also, the infamous anti-alcohol episode "Beer Bad".
Xander: And was there a lesson in all this? Huh? What did we learn about beer? Buffy: Foamy! Xander: Good. Just as long as that's clear.
Something of a Broken Aesop in this case since the bad effects weren't caused by the beer; they were caused by a magic potion that happened to be administered via the beer. Possibly this sequence is why the TV Tropes anon-edit password used to be "foamy".
In the sixth season, there is an entire Anvilicious plot arc about Willow becoming addicted to magic, complete with her going to a dealer. Since up until this point magic had been used as a metaphor for lesbian sex, it comes across as particularly tone-deaf.
Riley's blood-addiction thing is a metaphor for drugs (which is also played with in Angel, to an even further degree).
One running theme throughout this show. Perfectionist Annie's backstory is that she got highly addicted to medication, which eventually culminated in a mental breakdown and losing her scholarship. Shirley was once an alcoholic (and it's hinted that the addiction helped caused her divorce). In season 2 Pierce gets addicted to painkillers, and ends up passed out on a park bench before being hospitalised.
One episode also features the Study Group being forced to do a play to kids about why drugs are bad, with Pierce playing drugs - but doing it such a cool way that the kids love drugs. However, when Pierce storms out, he's replaced by Chang, who is incredibly scary and mean - and thus the highly accurate moral of "drugs will turn on you" is made by mistake.
On the other hand, Britta is known to occasionally use recreational drugs, and is perfectly fine.
Deep Love: Kenji's drug addiction is very much this, showing his fall from grace as a Pretty Boy host, to begging for money and owing money to violent loan sharks.
Dinosaurs: Both played straight and played with in this early 90s live-action/rubber suit sitcom. They do a very straightforward Drugs Are Bad episode about the characters finding and abusing a plant implied to be marijuana until one of them just accidentally burns the whole thing while high. At the end, they avert the usual PSA segment about how bad drugs are, when the adolescent son begs the audience to not do drugs so sitcoms can stop getting pushed to makeVery Special Episodes.
The episode "Gridlock" involves a virus that mutated from an incredibly addictive drug named "Bliss", which wiped out a whole city.
On that note, unearthedWord of God from The Sixties describes regenerations "as if [the Doctor] has had the LSD drug and instead of experiencing the kicks, he has the hell and dank horror which can be its effect". No wonder why he might suffer from regenerative trauma after the process.
The expanded universe story "Wonderland" deals with the damaging psychological effects of hippie drug use through the medium of a form of LSD that allows users to hallucinate monsters into existence before killing them.
Dragnet: This 1960s show handled this with all the finesse of a sledgehammer to the face. There was the couple who was so busy getting high that they let their daughter drown in a bathtub. There was "Blue Boy" who dosed on LSD and buried his head in the dirt while "painted up like an Indian and after chewing the bark off a tree. Sgt. Friday also told us about the guy who dropped acid and pulled his own eyes out so he could "get a better look", about the teenagers in San Jose who went blind from staring into the sun while on an LSD trip and lectures a group of people on how marijuana irreparably destroys your judgment, but alcohol doesn't.
Hawaii Five-O brought us "Up Tight", the sad tale of a young woman who jumped off a cliff and the Timothy Leary Expy who gave her the stuff... said to be "speed" all the way through the episode, but it was clearly acid. Also from this show, "Two Doves & Mr. Heron", which isn't about drugs per se, but a friend of the "two doves" dies of an overdose.
Marcus Welby MD had "Homecoming", about someone having flashbacks after having been "addicted" to LSD.
In The Young Lawyers episode "The Whimper of Whipped Dogs", Aaron bails out a former fiancee who's become a badly deteriorated heroin addict. Writer Harlan Ellison says the episode as you saw it had so much important parts cut or rewritten that it was a farce compared to his original hellish tragedy. (His version is reprinted in The Glass Teat volume 2.)
The Fresh Prince of Bel-Air: The episode "Just Say Yo" has Will being offered amphetamines so he can stay awake, and Carlton takes some from Will's locker thinking they're vitamins and almost dies as a result.
Fringe: Averted Trope as often as possible. Drugs play a significant role in solving several cases, Walter uses psychotropics all the time (on himself and others), and as of episode 3.19, which is called "Lysergic Acid Diethylamide", Astrid Farnsworth is the only main character who hasn't been under the influence of drugs onscreen at some point.
Gossip Girl: Averted Trope. Nate and Chuck do drugs on a seemingly regular basis with no ill effects thus far. One of Serena's one-nighters OD-ed in a flashback, but they didn't really overdo the Drugs Are Bad point (thankfully).
In one episode, kids who get high on heroin like to throw rocks through the windows of a school that teaches illiterate adults how to read.
In another episode, local youths use remote-controlled planes to smuggle drugs for some reason. Supposedly, this is to get the drugs across the border.
Home Improvement: In one episode, Tim and Jill catch Brad with marijuana and try to convince him that using marijuana is bad, but it is portrayed in a more even-handed way than in many other shows. Jill ends up revealing that she smoked pot in college and once while high bought a stash that was laced with something and she ended up in the emergency room and then was charged with possession and Tim had to bail her out of jail. The end. message was that while marijuana might not be inherently bad it can cause the user to make bad decisions and the potential risk is not worth it. Tim Allen himself rather famously spent a few years in prison for selling drugs, so he'd know.
House: The title character is addicted to Vicodin and isn't above criminal means to ensure a steady supply. This is partly a reflection of the fact that he's a Sherlock Holmes Expy (though Holmes' drug taking would have been legal at the time).
How I Met Your Mother: the characters smoke pot on occasion, no big deal is made out of it and eventually they decide they are too old for such proclivities.
Intervention: May be the strongest argument ever made against drugs. Or the not-so-awesomeness of having a serious disease; Intervention certainly doesn't really moralize about their choices and covers more on the aspect of people having a serious disease and how their drug use is more of a symptom of that disease than the actual cause.
JAG: In the episode "JAG TV", Harm investigates a sailor on an aircraft carrier who apparently committed suicide by jumping in front of a F-14 during landing. Turns out the reason was his drug use plus other personal problems.
When Creative has to work on a Saturday to come up with ideas for a new Bacardi Rum campaign, Kinsey (Sterling Cooper Creative's resident Pretentious Intellectual) makes a point of saying how much he is inspired by "Mary Jane." He tracks down some marijuana (that is, he calls an old college buddy of his to bring it into the office), and he and one of the other Creative guys starts smoking it, having engineered to get Peggy out of the office. She storms back in, and very pointedly says "My name is Peggy Olson and I'd like to smoke some marijuana." Not only does she seem to really enjoy being blazed, she ends up actually finishing the assignment by the end of the episode. It potentially crosses over into Inversion territory when Peggy's secretary Olive, a rather conservative older woman who'd been warning Peggy about how bad it was, receives a (completely stoned) lecture/Reason You Suck Speech from Peggy about how she (Peggy) was going places and how Olive had already decided not to (more or less).
Peggy also smokes up in Season 4, after visiting what appears to be an outpost of The Factory, when it is raided by the police. She successfully hides, avoiding arrest.
The writers do, however, appear to have a problem with heroin: when (commercial artist and Don's first flame in Season 1) Midge comes back in Season 4, she's prostituting herself to pay for her habit.
M*A*S*H: Has one episode where Winchester starts abusing amphetamines, right after he lectures Klinger about the stimulant's many deleterious side effects when he asks for them. Sure enough, those exact side effects kick in and Winchester is a wreck by the time Hawkeye and BJ discover what he is doing and convince him to stop.
One very special episode had him and his friends accidentally acquire a pile of marijuana - these career criminals who spend most of their time drunk react with horror to the stuff, and the folks using the stuff act unlike anyone stoned, ever. It had to be a parody - HAD to be...
Perhaps I'm not remembering it entirely accurately, but as I recall they were simply worried about the consequences of getting caught with so much marijuana, and weren't particularly concerned with any moral implication.
It wasn't even to do with the consequences, it was because of Joy's logic that went along the lines of 'If you get drunk, you throw up and get thin. If you smoke pot, you get the munchies and get fat.'
In an early episode of The Nanny (second episode, in fact), Brighton complained about how he wasn't popular in school, and Fran told him about a kid she used to know who tried smoking to do that; unfortunately, Brighton got the wrong message, and tried to one-up that guy, by doing it himself (not Fran's intention at all), and got caught. At the end of the episode, Fran Scared Him Straight by taking him to the retirement home where her grandmother Yetta, an addicted smoker who was clearly showing the adverse effects of doing it her entire life, lived. (And to drive the point home, Yetta was all-too willing to show him a few of the other residents who were even worse off, which thankfully, happened off screen.) It worked like a charm.
Noah's Arc: Played in with in a counterintuitive way in the movie. When Brandy crashes Noah's wedding we get to see her enjoy a variety of drugs, and its all Played for Laughs with no real consequences. On the other hand, Alex's addiction to caffeine pills is taken seriously by Noah, and that's where the Drugs Are Bad aesop is played out.
Punky Brewster wants to join a clique who call themselves the Chiclets. But in order to join, she has to try drugs. Punky is faced with a quandary until she follows a "Just Say No" campaign. The episode ends with Soleil Moon Frye doing a Just Say No rally in Atlanta and Cherie Johnson doing a campaign in St. Louis.
Revolution: In "Sex and Drugs", Drexel is the personification of this trope. He has poppy fields, which is how he gets the heroin in which he deals. Drexel and a whole squad of goons live in a luxurious mansion as a result of his heroin business. He also reveals that he is the largest heroin supplier in the Monroe Republic, because he paid Miles Matheson, back when Miles was a general in the Republic, large amounts of gold to remove all his competition. His only opposition is a family of Irish cops named the O'Hallorans, who have burned his poppy fields. Bill O'Halloran, the patriarch, reveals that his daughter Rebecca ran away because she wanted a glamourous life with Drexel, and Drexel got her addicted to heroin, killed her and sent her body back to Bill.
Sex and the City: Subverted Trope. Carrie, Miranda and Samantha smoke pot sometimes. Once, when the women were asked where were they going to score some weed, Samantha's response was, "Well, I'd call my dealer, but he's at the Cape."
Small Wonder: In "Vicki and the Pusher", a schoolyard bully tries to get Vicki addicted to narcotics. Vicki takes the drugs home, but she doesn't consume them. Later, the Lawson family help the police conduct a sting at the school.
Spaced: Averted Trope: Recreational drug use is everywhere in the series and is either not a big deal or Played for Laughs.
Stargate SG-1: Late in this show, a cartel of drug runners called the Lucian Alliance formed in the power vacuum left by the fall of the Goa'uld. The SGC responded by mounting raids on their shipping. They end up as the Big Bad of Stargate Universe for much of its run.
Subverted Trope. The main characters smoke pot almost every episode and rarely faced negative consequences as a result. Even after being caught, the characters continue to do it like it never happened.
Further parodied in the episode "Reefer Madness." Red imagines Eric getting convinced to try marijuana by Hyde in a take-off of the Reefer Madness movie, in which Hyde shoots Donna, Eric goes incurably insane, Jackie dances to really fast music, and Kelso ends up with random laughing fits.
Because the idea of monstrous aliens blackmailing the human race for ten percent of their children apparently wasn't far enough over the Moral Event Horizon, Day Five of the mini-series Children of Earth had to reveal that the aliens were using the kids to get high.
Traffic: The British miniseries, and the American film adaptation, have the message "Drugs are bad, but there aren't any easy answers (possible solutions, but not easy ones)."
V: Subverted Trope. In V: The Final Battle, the street smart member of the resistance is selling drugs to Visitors and their collaborators. When his father confronts him on this, the character justifies it as a means to help undermine their enemy in some small way and his father admits he has a point.