If there's any way you can get your children to watch "Epidemic!" at 8 tonight on Channel 5, do it. Do it if it means signing a note excusing the undone homework. Do it if it means chaining them to the TV set.

The subtitle of "Epidemic!" is "Why Your Kid Is On Drugs."

If he or she isn't, and it makes you feel better, read it with one of these substitutions: Why your neighbor's kid . . . Why your kid's friend . . . Why somebody else's kid . . .

And one more thing, alcohol is a drug. Believe it. In any case, you will after you've watched what this glossy and persuasive documentary has to say.

The basic message is simple. We're losing a generation to drugs: cocaine, speed, Quaaludes, even paint solvents, but most especially to marijuana and alcohol. The hour-long documentary will be followed by another hour of discussion among substance abuse experts in this area, parents of drug users and questioners from an audience at the University of the District of Columbia, where the local segment was taped.

It is conventional wisdom among youngsters that marijuana doesn't hurt you.

Nowhere other than tonight's program has that folklore been so impressively refuted. Studies of rhesus monkeys demonstrate that the drug suppresses reproductive hormones and can kill or permanently damage unborn fetuses of user mothers. But most horrifying is the apparent onset, in a man barely out of his twenties, of a kind of senile dementia. Brain scans indicate that his daily use of marijuana over a period of years has caused an encrustation of the spaces between neurons--brain cells -- so that the brain's normal electrochemical functions have been short-circuited. In other words, he has lost his memory exactly like an old person who is considered senile.

"Epidemic!" producers say it should be no surprise that 3.3 million American teen-agers have trouble with alcohol abuse. Yet alcohol, the experts note, is "far more toxic than all the drugs of abuse put together."

It is the third leading cause of death, says one physician -- not just in itself, but through drunken driving, alcohol-induced cancers and alcohol-induced cardiovascular or liver disease.

And why not, asks the narrator, to a backdrop of TV beer commercials all promising good times, good fellowship, sex, fun, adventure, beautiful people. . . . Even peer pressure, that all-time seducer of teens into the "in" group, cannot equal TV, song lyrics and movies in their message that stoned is good and escape from reality is all there is, that if you feel bad there is a pill to take, if you have a headache, get rid of it fast, fast, fast . . .

"Epidemic!'s" employment of techniques often used in the TV commercial rather than the TV documentary makes the program an effective weapon in countering the supergloss of a typical TV beer ad.

The program is a syndicated project -- Gannett broadcasting's first -- and has been or will be shown in about 40 major TV markets.

Last spring, Dallas and Houston stations combined forces to produce a Texas-wide version of "Epidemic!" and aired the two shows back-to-back. They counted 150,000 phone calls -- until the Houston phone circuits blew.