(FORTUNE Magazine) – Drugs in their variety affect users in a host of ways -- no single physical symptom provides sure evidence that someone is abusing them. A boss who suspects that a subordinate has a problem should look for behavioral changes -- the person is absent increasingly, exhibits radical mood swings, or begins working in frantic, spasmodic bursts. ) If drug-taking seems the most plausible explanation for such changes, the boss should at least question the employee. If the evidence of drug abuse is irrefutable, the best course is usually to stage an ''intervention.'' This is a common procedure in which a boss, co-workers, friends, and family, together with a counselor, gather and confront the addict in person. Usually this is enough to get him to acknowlege his problem and say that he'll accept help. If he does, he then goes off immediately under the counselor's care for detoxification and, subsequently, rehabilitation. Drug-treatment professionals offer the following advice: Tackle the problem early, when recovery is still possible. Get professional help immediately. Before selecting an intervention counselor, find out how much experience he has had with this type of case. Don't try to counsel the executive yourself. He may get the false sense that you're giving him all the help he needs. Document the deterioration in the executive's performance. Present your information in a factual, firm way. Leave off-the-job behavior to the spouse, family members, or friends. Keep confidential the fact that an intervention is being planned. Three days before a scheduled intervention with the head of an insurance firm, his wife told him of it. Denying he had a problem, he threatened to retaliate if the family and friends proceeded. The intervention never happened. Shortly afterward, in a stupor from drug-taking, the executive asphyxiated himself. Don't be overly sympathetic at the intervention. Allow the executive to feel the full weight of what he is being confronted with. Make sure that the executive enters a specific course of treatment agreed on with the counselor beforehand. Promise the executive complete confidentiality if he will accept treatment, and agree to pay for the treatment. If the executive resists treatment, deliver an ultimatum -- that his job is in jeopardy if he doesn't get help. Besides your company's employee assistance program, other sources of information include: The local chapter of the American Medical Association. A nearby mental health center or mental health association. A drug crisis hot line, like 800-COCAINE. The National Association of Alcoholism Treatment Programs, in Irvine, California, an organization that despite its name also offers help for problems of drug abuse.