* A couple of new films take strong stands against drugs. I'm Dancing as Fast as I Can deals with the abuse of medically prescribed substances such as tranquilizers. At first, the main character finds it easy to deny her addiction since her doctor has sanctioned and even recommended the drug, to ''control her symptoms.'' When she starts withdrawing from dependence, the process is graphically depicted. The first half of the film is both grimly effective and savagely funny as it burrows into the personalities of the woman fighting for freedom and the insecure boyfriend who tries to help her. The second half is less bold and less involving, leading to a trite resolution of the story. The director was Jack Hofsiss, the whiz of Broadway's ingenious ''Elephant Man'' production, in his movie debut.
Christiane F. comes from West Germany, where it was directed by Urlich Edel. The title refers to a teen-age girl -- based on an actual person -- who joins her friends in toying with drugs, then sinks into a nightmare of addiction and prostitution. To its credit, the film never hints at glamorizing its sad subject. But its details are so harrowing and at times so disgusting, that many viewers will be turned off before the message has a chance to get across.