In the headache business, they're called losers : the patients who don't respond to anything.

They change doctors like underwear, and they pop pills with painful abandon.

They're prime candidates for drug abuse, because when your head hurts like that all the time, you'll do almost anything . . . .

"Twenty years age," says Dr. Seymour Diamond, executive director of the American Association for the Study of Headache (for doctors) and of the National Migraine Foundation (for those with the headaches), "we had nothing. All we could say was, 'Well, you'll just have to live with it.'"

It is not nearly as hopeless today for the approximately 45 million Americans whose heads hurt badly enough to send them to the doctor. And not even for the third of them who get genuine migraines, that granddaddy of sick headaches.

But even with major leaps in understanding the mechanics of various headaches and even greater leaps in therapies, there are still sufferers for whom relief has not yet been found.

The 500 or so physicians from around the world who belong to AASH are constantly looking for new ways to help, and last week around 200 members met in Washington to compare notes on latest techniques, discoveries and useful drugs.

Dr. Diamond, whose Chicago headache clinic is one of the country's largest, was one of the early proponents of biofeedback training for migraine- and some tension-headache patients. He still finds the technique extraordinarily successful with some patients. Hypnosis works with others, and now one -- or another -- class of drug developed for ailments quite other than headaches . . .

Some of Diamond's own recent research has centered around indomethacin -- an anti-inflammatory drug developed for arthritis -- for treatment of "exertional" headaches: those that strike victims after some form of exertion, either passive (such as a cough), or active, like running, sexual activity, bicycle riding. (This kind of headache can suggest serious disorders like brain tumors, aneurisms or some kind of arterial malformation, warns Diamond, so all such patients should be examined exhaustively with skull X-rays and so-called CAT scans). He has found that some patients who have no other disorders respond positively to the drug.

Among other findings reported by major headache-research physicians:

Patients who get "classical" migraine headaches (with pre-headache visual disturbances) tend to be more prone to motion sickness and dizziness than other headache victime, including "common" migraine sufferers.

More than 50 percent of headache patients surveyed in Michigan said they "felt they were regarded socially with fairness and compassion, with regard to headache," but 25 percent said "they felt they were the object of negative attitudes or social neglect because of their headaches."

Migraine patients who use ergotomine as maintenance therapy may be subject to "rebound" headaches when the drug is withdrawn.

But the most exciting new field of research for migraine sufferers, believes Diamond, may be in the use of the new so-called calcium antagonists, a class of drugs which has shown extreme promise in the prevention of cardio-vascular spasms and arrhythmias.

The drugs are not yet approved in this country for cardiac use, and their application to treatment of vascular headaches like migraine is just beginning to be studied formally. In a small pilot project preliminary to a full-scale study, however, Diamond tried the drug flunarizine on 20 "intractables," or "losers."

"Before I ever undertake something with a new drug I like to get a feel for it," says Diamond. "These were people we'd tried everything on, all types of therapy. This drug wasn't uniformly effective, but we did have five people who were losers who became winners."

"One woman," he says, "had seen close to 20 different physicians and been to five different headache clinics. She was running about two headaches a week, and although she wasn't habituated to anything (drugs), she was incapacitated at least three days out of the week from carrying on any normal activity. She had been tried on all types of drugs and biofeedback therapy. She'd had a course of hypnosis and tried acupuncture.

"This lady had been around, and she wanted help."

She volunteered for the study and now, seven months later, she has "maybe one headache a month." She continues on the drug as a "compassionate" user, permitted to use it even though it is not yet approved by the FDA for use here.

The other four cases are similar, says Diamond. "These won't replace the drugs like Propranalol (another drug developed for high blood pressure which has helped many migraine patients), but it gives us one more thing to try."