The season 4 episode "Blood Brothers" features heavy usage of crack. It is no way promoting it and shows its negative effects of it.
Main protagonist smokes three cigarettes at once in the Pilot; however, it was a trick to see the laser rays. Besides this, he never smokes or drinks alcohol.
"Twenty questions" (S6E4) features protagonist's fight to prevent his 15-year-old friend's alcoholism; scenes of excessive beer consumption and intoxication of teenagers is shown twice in this episode, with adverse effects of alcohol and bad peer-pressure is emphasized.
You see the occasional use of alcohol and cigarettes with some episodes showing harder drugs like prescription pain meds or crack. Sometimes the main character is drugged in order to get information out of him or to try to keep him from stopping whatever bad thing they are going to do.
Occasional smoking, consumption of wine or other alcoholic beverages. Mostly shown as used in moderation.
Smuggling, production or possession of heroin, cocaine, methamphetamine and PCP is shown in various episodes, always by the villians.
Illegal drug operations are severely fought against by the allied characters, and the main protagonist frowns upon the use of tobacco and alcohol products.