When the Rev. Dmitri Dudko, a dissident Russian Orthodox priest, unexpectedly appeared on Soviet television last June and confessed slander against the state, he stunned human rights advocates in the U.S.S.R. and abroad.

But many of his followers, or "spiritual children," refused to believe that his recantation was genuine, coming as it did after six months in prison and secret interrogations.

A recent report from Moscow received by the New York-based Research Center for Religious and Human Rights in Closed Societies suggests that Father Dudko's televised about-face confession might have been drug-induced. The Rev. and Mrs. B. S. Hruby, leaders of the Research Center, said they considered the report authentic and its sources unimpeachable.

According to the report, Dudko, 58, was held for two months in a jail cell in Moscow's Lefoto Prison after his arrest on Jan. 15. He then was transferred to the psychiatric ward of the prison hospital, where he spent nearly four months under "medical" treatment.

After his appearance on Soviet television June 20 when he read a statement saying he had yielded to "propaganda voices directed at undermining our system," the hero of the Soviet religious freedom movement was released from custody.

He was not immediately allowed to return to his home parish in the village of Brabnevo, about 50 miles outside the capital. Instead, he was sent to another out-of-the-way parish, nearer Moscow, where some of his followers managed to call on him and witnessed what the report said was his "erratic behavior."

Said the report: "He would come to greet his visitors at the door dressed in his underwear, then fail to acknowledge them, go to bed, turn to the wall and fall asleep."

Father Dudko's "somnolence and peculiar conduct lasted two weeks," the report continued, "after which he began acting normally, but would not refer to his televised confession, to his hospital treatment or to the period immediately following his release."

The priest then was permitted to return to his home parish, the report said, but "acquired, obviously without his consent, a 'secretary' who presents herself as his 'spiritual daughter.'"

According to the report, the woman is "extremely solicitous" and "insists on accompanying Father Dudko everywhere he goes outside his home, even to his medical appointments [and] opens all his mail and closely watches all his contacts."