BALTIMORE, DEC. 12 -- Johns Hopkins Hospital, facing opposition from many of its 1,568 doctors, has backed away at least temporarily from an unprecedented plan to require the doctors to undergo periodic drug and alcohol testing.

Announced in February and originally set to go into effect last July, the urinalysis program encountered unexpected resistance from staff doctors, who said that such testing would be unreliable and overly intrusive.

The hospital's medical board, consisting of department heads and other top leaders, voted Nov. 27 to put off the testing indefinitely, giving the hospital more time to persuade rank-and-file doctors to accept it.

Hamilton Moses III, the hospital's vice president for medical affairs, said the controversy "has not weakened our intent to ask the hospital's medical staff to squarely face the significant social problem of substance abuse or the intolerable situation in which only some health-care workers are tested, but not others."

The testing program, which Hopkins officials said would be the first of its kind in the nation, would require each doctor to be tested every two years during "re-credentialing," a period of several weeks to months in which doctors are evaluated for reappointment to their jobs, according to hospital spokeswoman Carol Pearson.

If a doctor were to test positive for drug use, she said, another test would be done to make sure the first test was accurate, and then the doctor would be offered counseling or treatment if the first test's results were confirmed. Tests indicating drug use would not be automatic grounds for suspension or dismissal, Pearson said.

Although the hospital played down the postponement, staff doctors saw it as a victory. "The bottom line is that this is a major retrenchment by the hospital," said cardiologist Sidney Gottlieb, chairman of the hospital's faculty council.

He said several other key physician groups, including the hospital's ethics committee, oppose testing and may succeed in stopping it altogether.

Meanwhile, the hospital said it is going ahead with a modified plan on Jan. 1 that will require most job applicants, including doctors, to undergo a one-time drug and alcohol test.

Applicants will be tested for alcohol, barbiturates, cocaine, marijuana, PCP, heroin and other opiates. Under current policy, employees are subject to testing only if drug use is suspected.

In a carefully worded news release, the hospital said its board of trustees agreed with the medical board to postpone routine drug testing of its physicians but looks forward to "eventual implementation."

The statement added that the trustees asked that a "more intensive education effort be made with the medical staff to increase acceptance of across-the-board testing . . . ."

Hopkins's decision to be a leader in physician testing did not stem from any particular incident at the hospital, officials said, but from the medical board's concern about increased drug abuse in society as a whole.

Doctors have complained there is no statistical evidence that drug and alcohol abuse is severe enough among doctors to justify what they see as the heavy-handed and intrusive requirements of testing.

"It creates a witch hunt atmosphere," Gottlieb said. Also, he said, testing is so unreliable that if "you eat a poppy seed bagel, you're going to test positive for marijuana." Professional reputations could be ruined, he added.

However, hospital spokeswoman Joann Rodgers said the testing program is "not designed to punish . . . . This is a program to find physicians who need help and to save their careers and their expertise.

"We recognize their {privacy} concerns," she said, "but those concerns are not so important as protecting patients from the possibility of harm by an impaired physician."

Gottlieb acknowledged that some doctors abuse drugs and alcohol, "and that could be the reason for their opposition" to testing. But he contended that the incidence is small and should be handled voluntarily by "more widespread education and treatment."

A Harvard School of Public Health study in the early 1980s indicated that 10 percent of physicians sampled in New England reported using drugs at least once a month.

J. Michael Compton, acting executive director of the Maryland Board of Physician Quality Assurance, said the board has disciplined 27 doctors in the state since mid-1988 for "drug-related reasons." He said some were accused of using drugs, others of selling them.