Powerful new implants and injections could soon revolutionize the treatment of schizophrenia and address the perennial concern of doctors and families that patients who stop taking their medicines may relapse into psychotic behavior. The new techniques could deliver medicine for weeks or even months at a time.

PROPONENTS SAY SUCH treatments, now in varying stages of development, could eliminate problems with patient compliance if they become widely prescribed.

The new techniques are collectively known as "long-acting" medicines because they involve injections that last for long periods and implants that release drugs slowly. The treatments will not cure schizophrenia, but doctors say they can help patients control their illness, with its delusional or disordered thinking and hallucinations, because they won't have to remember to take their medicine nearly as often.

Some advocates for the mentally ill are worried that new approaches could lead to coercive treatment. Proponents say the new technologies can increase patient choice while lowering the risk of side effects.

"Because it's a mental illness, there is much more fear of coercion," said John M. Kane, chairman of psychiatry at Zucker Hillside Hospital in Glen Oaks, N.Y. "But I think that may not take into consideration the nature of these diseases and how devastating they can be and how critical it is to prevent relapses and rehospitalization."

The antipsychotic medicines currently approved in injectable form in the United States come from an older class of drugs that cause severe side effects in many patients. Newer medicines called atypical antipsychotics have largely replaced the earlier drugs, but have not yet been made available in long-acting form.

Now, Janssen Pharmaceutica Products L.P., the maker of risperidone, the country's most frequently prescribed atypical antipsychotic, is applying to the Food and Drug Administration to market an injectable version. Janssen said injectable risperidone has been approved in the United Kingdom, Germany, Austria, New Zealand, Mexico, the Netherlands and Switzerland.

Steven Siegel, a psychiatrist at the University of Pennsylvania, recently unveiled a device the size of a quarter that could be implanted in patients with schizophrenia. Siegel hopes the implants, which have yet to be tested in humans, could one day deliver antipsychotic medicine for a year at a time.

TREND CONTINUES

It is difficult to predict when long-acting antipsychotics with the latest drugs might reach the market - but the trend toward these products is unmistakably on the horizon.

"In schizophrenia, we know that by the end of two years, 75 percent of people are not taking their medicine," said Samuel Keith, chairman of psychiatry at the University of New Mexico in Albuquerque, and a former chief of schizophrenia research at the National Institute of Mental Health.

Keith said everyone finds taking medicine difficult - people given a course of antibiotics often find they have a couple of unused pills by the last day. With schizophrenia, this forgetfulness can be compounded by the delusional and disordered thinking that are hallmarks of the illness.

"There is a part of logic that says, 'If I don't take a medication, that proves I don't have the illness,' " said Keith, who has helped test the injectable form of risperidone for Janssen.

"So someone with schizophrenia will say, 'I'm not going to take my medicine,' and the next morning they don't feel different, so they don't take it that day, either. For a couple of months, you can get away with it, but ultimately you will relapse."

Relapses can be terrifying and involve patients' hearing voices, seeing hallucinations and being unable to distinguish illusion from reality. Doctors say each relapse takes something from patients, leaving them with a longer, harder climb back to normalcy.

Kane said that hospitalizations, suicidal or aggressive behavior, homelessness and lost jobs can follow. "Within a year, about 60 to 75 percent [of patients] will relapse without medication," he said in an interview.

PSYCHIATRISTS' INPUT

A major reason psychiatrists like long-acting medicines is that they facilitate monitoring patients, since the implants would be put in place by a surgeon and injections would be administered by a nurse or another professional.

"If someone is on oral medicines, they could stop taking their medicines, and no one would know," said Kane, who also helped to test the injectable form of risperidone.

If a patient did not show up for an injection, however, Kane said doctors would have a couple of weeks, during which the previous shot was still potent, to make arrangements to bring in the patient for the follow-up injection.

The prospect of such techniques is raising concerns among some patients that the new treatments will be used coercively, effectively replacing the locked wards of mental institutions with what one advocate called a chemical straitjacket.

As states consider shifting laws that allow the forcible hospitalization of some psychotic patients to laws that force outpatient treatment, these advocates worry that injectable medicines may get used against the wishes of large numbers of patients.

"We hate the word 'compliance,' because it makes it sound like we have to be good little boys and girls," said Nancy Lee Head, who has schizophrenia and runs support group programs in Washington for the National Alliance for the Mentally Ill and the DC Mental Health Consumers' League.