A College Park psychiatrist and two of her assistants have been sentenced on charges of improperly prescribing drugs to scores of patients.

A social worker and an unlicensed therapist working for the psychiatrist, Velma E.L. Powell, illegally wrote prescriptions on slips signed in advance by Powell, prosecutors said. The assistants also switched patients' medications and dosages for powerful tranquilizers and pain killers such as Valium and Demerol, often with little supervision by Powell, according to the prosecutors.

Under Maryland law, only physicians can prescribe drugs.

Some patients with schizophrenia, depression and suicidal tendencies were hospitalized, an unnecessary step "if they had been properly monitored" by a doctor, said Gale R. Caplan, chief of the Medicaid fraud unit in the Maryland Attorney General's Office.

The case against Powell, 41, therapist Joyce V. Woods, 45, and social worker Karen E. Fryer, 35, came after an undercover probe in which investigators posed as patients at Powell's office and a Baltimore grand jury subpoenaed office records that prosecutors said were fabricated or altered.

Powell was fined the maximum $100,000 in Prince George's County Circuit Court on April 3 on charges of illegally prescribing drugs and conspiring with Woods and Fryer to enable them to practice medicine without licenses.

Powell also was ordered to reimburse the state $20,000 for the cost of the investigation.

Powell entered a so-called Alford plea, in which she did not admit guilt but acknowledged the evidence against her could lead to conviction. In addition, Judge Robert J. Woods sentenced her to probation before judgment, which means that after serving five years' probation, she could seek to have her record expunged -- which could make it possible for her to retain her license to practice medicine.

Woods was fined $10,000 this week in Baltimore Circuit Court and given three years' probation on charges of obstructing justice by fabricating patient records sought by a grand jury. Woods also entered an Alford plea.

Fryer was sentenced last May to probation before judgment in Prince George's District Court after pleading guilty to practicing medicine without a license.

Prosecutors said the alleged irregularities occurred from 1984 to 1988 at Powell's office in the 6200 block of Greenbelt Road, where she treated both Medicaid and private patients.

According to prosecutors' statements filed with the court, Fryer said she refilled many prescriptions on her own for a "large variety of medications," including Percodan, the anti-depressant Thorazine, estrogen for menopausal women, antibiotics, steroids and various hormones.

In 1988, the Medicaid fraud unit sent two undercover investigators to Powell's office, one claiming to be suffering from agoraphobia, an abnormal fear of being in open or public places. Powell prescribed an anti-depressant drug called Xanax, then turned the "patient" over to Fryer, the statement said. In subsequent meetings, according to the statement, Fryer switched from Xanax to a drug called Prozac and later increased the dosage of Prozac, apparently without Powell's supervision.

When investigators seized records in Powell's office for the grand jury, according to the statement, experts discovered several pages in Woods's handwriting had been fabricated or altered to make it appear that Powell had approved prescriptions.