Not for nothing, apparently, did bartenders in western movies once greet customers with the phrase "Name your poison." Perhaps they should have been taken literally. As the expanding television literature on drug abuse has made tearfully clear, increasing numbers of young people are virtually poisoning themselves on excess.

WRC-TV takes a tiny breather from promoting its local newscasts tonight for a prime-time informational special on drug abuse, "If You'd Only Listen," at 8 on Channel 4. Though anything but imaginatively produced, the hour contains powerful, high-impact testimony from recovered or recovering young abusers of alcohol and other drugs. There is also a rather low-impact four-minute interview, near the end of the hour, with Nancy Reagan, who has made fighting drug abuse a personal crusade.

Reporter Susan King asks Mrs. Reagan the crucial question "Why?" Why is drug abuse on the rise? Mrs. Reagan says "the two main factors" are "peer pressure" and "very poor self-esteem" on the part of the abusers. But these are virtual constants. She ignores King's suggestion that something in modern American society might be to blame. Drug abuse is the kind of problem whose effects are so profound that just about everyone has given up looking for a cause.

It's all damage control now.

Ricky, 15, started taking drugs in the seventh grade because, he says, he wanted to be part of "the in crowd." Alma, 16, started smoking pot at 12 and became addicted to PCP; "I was screamin' a lot," she recalls, and hallucinating elephants. Dan, 17, started using drugs at 12, turned to burglary to pay for his habit and once tried to hang himself with a bed sheet. Nicole, 16, began drinking at 12, eventually became so enslaved to various drugs that she cut her arms with a razor and wrote "I hate you" to her parents in her own blood.

The stories are horrifying, but there's a stirring determination in the eyes of some of those who have been to the brink. Young people inclined toward experimentation with drugs may or may not be affected by what is shown tonight (may not even bother to watch, of course) but certainly there is great credibility in the first-person accounts of those who saw their lives, and the lives of those around them, all but destroyed. As a justifiable scare tactic, a program like this has to be more valuable than public service announcements from intimidating pop stars like Mr. T.

Producer David Bartlett and executive producer Kathleen McCampbell decided to waste the first quarter of the program by opening the hour with a short, locally produced film, "The Glug," about a child whose abuse of alchohol almost kills him. It is well acted by a nearly all-kid cast, but its presence on tonight's program delays the most potent material in it, and seems to serve more as padding than as edification.

In addition, the producers chose to identify the participants with splashy, and inappropriate, electronic graphics that combine a freeze-frame with a hokey print display accompanied by the amplified splatter sound of an electric typewriter. Such sloppily disruptive bursts of schlock-tech add nothing to delivery of the message. The producers give new meaning to the phrase "substance abuse" by abusing the substance of their own program.

Despite the witlessness of those who made the program, and despite the grim nature of what the youthful witnesses have to say, "Listen" is hardly without hope. Linda, 21, a former drug abuser who is now a drug counselor, utters the most inspiring words heard on the program: "My parents never gave up on me." Any parent who can get his or her kid to watch this show is probably doing both of them a favor.