In *The Office * thread we were talking about Ryan’s possible drug addiction and I wondered how he could be considered an addict after only one episode of him using, and Hal Briston (and others) said:
I’m wondering what other sitcoms have had drug addicted characters. None come to mind right off the bat, but I thought it might be an interesting thread topic. Who else’s drug problem came up so quickly like Ryan’s? It was a one episode instance for him, but I was told to assume he is a habitual user.
Just sitcoms? Nothing springs to mind, though there have got to be a few examples. Of course, if you include alcoholism (and IMO you should), there are plenty. Homer Simpson, Norm Peterson (Cheers), John Larroquette’s character on The John Laroquette Show (recovering). Gobs more, I’m sure.
The uncle on Family Ties, played by Tom Hanks, was an alcoholic.
Will and Grace had Karen, alcoholic and addict to any number of drugs.
Absolutely Fabulous, the two leads were both alcoholics and drug addicts.
I always got the impression that Norm was addicted not so much to alcohol as to sitting around in a bar.
Sam Malone on Cheers was a recovering alcoholic.
Hawkeye Pierce on MASH had a few episodes relating to problems with alcoholism, but I don’t remember if he stopped drinking.
For the most part, sitcoms try not to weigh themselves down with such dark themes, or deal with it in absurd ways (Absolutely Fabulous).
House is an addict, right? Vicodin or some such?
Oops, I missed that you were asking for sitcoms.
Charlie Sheen’s character, Charlie Harper, on Two And Half Men is clearly an alcoholic and a sex addict.
On the sitcom* Blossom *, the lead character’s older brother was a recovering addict. Unlike many other shows, this was a continuing (although occassional) story line.
On *WKRP in Cincinnati * the salesman (Herb Tarlek) admitted his alcoholism, went to AA and stopped drinking.
*Hill Street Blues * featured two alcoholics: Furillo and LaRue.
This is slightly different from substance abuse, but there was an episode of *Taxi *where Alex became addicted to gambling. It made an impact because Alex was typically seen as the most straight-laced person in the garage, and it took the usually off-kilter (and former drug addict) Reverend Jim to get him to realize that he had a sickness.
Is nicotine addiction on the table? Because that list is gonna be looooooong.
On “Criminal Minds,” Dr. Spencer Reid became an addict when a criminal with two personalities kidnapped him, one personality tortured him, and the other gave him Darvil. He evidentally kicked the drug and is now going to NA.
I hate it when that happens.
ETA: An episode of “Golden Girls” dealt with Rose’s addiction to pain killers after a back injury.
Overall a decent episode, but I really hate single episodes where it is ‘revealed’ that someone has had a major addiction for several decades, but it has never had an impact on their life until that episode and then is neatly cleared up over 30 minutes…never to be mentioned again.
Lucile Bluth (from Arrested Development) is what one may call a functioning alcoholic.
On That 70’s Show, Eric, Donna, Steven, Michael, Fez, Jackie, Leo, Bob, and Midge are all apparently suffering acute reefer madness, as cannabis addicts.
We could call Carla from Cheers a skank, but we could also consider her a sex addict (or heck, call her both!).
There was a guest star on Good Times who was a teen alcoholic–she kept locking herself in the bathroom which caused distress to JJ.
(god help me, I remember this).
I think Rhoda might have dealt with this topic, too. The original Bob Newhart show–half his clientele was addicted (to things other than substances)–but we might be stretching the definition a bit thin. 
(if we include OCD, we’re golden!)
Wasn’t there a character on Bewitched (uncle Arthur?) who was an alky, too?
Back when such matters were dealt with less seriously, you have Otis, the town drunk on The Andy Griffith Show . F Troop also had a town drunk named Charlie, IIRC.
Charles Winchester became addicted to amphetamines in an episode of MAS*H .
Mr. Wick from The Drew Carey Show had a substance abuse problem, and I recall that he was on the medication Anabuse for it.
I think Sonny the Cuckoo had a pretty serious Cocoa Puffs problem.
Andy Sipowicz on NYPD Blue was an alcoholic and through the course of the show’s run went from drunk to recovering drunk to relapsing to recovering many times. Many of the other cops were addicts as well…
I think Jesse from Saved by the Bell got addicted to speed at one point, leading to her attempting-to-be-serious-but-way too ridiculous breakdown: “I’m so excited! I’m so - Scared!”