An Alexandria judge has ordered a Northern Virginia physician to pay $550,000 in damages to an Alexandria kidney specialist for what the judge called the doctor's "particularly reprehensible" takeover of the specialist's medical practice.

In addition, Circuit Court Judge Wiley R. Wright Jr. awarded the specialist, Dr. Raphael J. Osheroff, half of any future profits from a competing Woodbridge kidney treatment clinic established later by his former colleague, Dr. Robert Greenspan.

Osheroff, medical director of the Northern Virginia Dialysis Center in Alexandria, was undergoing psychiatric care for severe depression and had left his practice in Greenspan's hands at the time of the alleged takeover in 1979, the judge said.

"Not only did Dr. Greenspan solicit Dr. Osheroff's patients, but he also engaged in a whole series of improper acts calculated to deprive Dr. Osheroff of his practice," Wright said in a decision handed down Tuesday.

The judge said Greenspan's conduct was "particularly reprehensible" because Osheroff was "suffering or recovering from a severe mental depression" while Greenspan was trying to take "unfair advantage" of him.

"What I did, I did to protect patients," Greenspan said in an interview yesterday. He said Judge Wright's decision would be appealed.

Two codefendants in the suit, Dr. Steven Tolkan and a nurse, Margaret Hess, former employes of Osheroff, both were cleared of wrongdoing by Wright.

According to court papers, Osheroff sold the Alexandria clinic and a similar clinic he owned in Fredericksburg, Va., to a Boston-based health care corporation in 1977. The corporation, National Medical Care Inc., retained him as medical director of the facilities under a profit-sharing agreement.

In 1978, according to Judge Wright's decision, Osheroff hired Greenspan and Tolkan to help provide medical care to kidney disease sufferers. On Jan. 2, 1979, Osheroff voluntarily admitted himself to Chestnut Lodge, a private psychiatric hospital in Rockville.

During his absence, Greenspan agreed to oversee the practice, the judge said. While Osheroff was at Chestnut Lodge, Tolkan received a $20,000 annual salary increase, with the knowledge of Osheroff's lawyer. Greenspan's salary rose from $45,000 to $100,000, "although Dr. Greenspan never mentioned it to Dr. Osheroff," Wright said.

Greenspan also received permission from Virginia health authorities in 1979 to open a new kidney clinic in Woodbridge, giving Osheroff's accountant the impression "the new unit would be jointly operated with Dr. Osheroff," Wright said.

Greenspan's application for the new unit, Prince William Dialysis Facility Inc., used information "gleaned in large measure" from Osheroff's Alexandria practice, according to the judge.

Osheroff returned to his medical practice in November 1979 and fired Greenspan the following month. Wright said that before Greenspan left he actively solicited Osheroff's patients to switch to the new Woodbridge clinic, in violation of medical ethics.

A written form soliciting business was presented to kidney disease sufferers "while many of the patients were undergoing dialysis and many of the patients became upset over the situation," Wright said in his decision.