WASHINGTON (AP) -- Someone sent free boxes of once-a-week Prozac to south Florida depression patients - people who don't take regular Prozac and hadn't even discussed trying the new version with their doctors.

It's not clear how many patients got the unsolicited Prozac, which came to light when one furious recipient filed an invasion-of-privacy lawsuit this week against her doctors, her pharmacy and Prozac maker Eli Lilly & Co.

Lilly is investigating and apologized Wednesday for the incident. The Food and Drug Administration is watching closely.

The case - apparently the first time a powerful prescription drug has been mailed, much like laundry detergent samples are - surprised medical experts who warned that unsolicited drug mailings are dangerous and may be illegal.

"I'm incredulous," said drug safety expert Michael Cohen of the nonprofit Institute for Safe Medication Practices. "It's a dangerous precedent. You might have (people) other than the patient picking it up out of the mailbox and taking it. It could be a child."

Laws governing prescription-writing and pharmacy practices vary by state. The drugstore chain Walgreens maintains it properly filled prescriptions from doctors' offices and mailed them for free because it had "coupons" from Lilly to provide reimbursement. The Florida woman's doctors aren't talking.

Lilly issued a statement late Wednesday saying it was inappropriate to mail medicine to patients without their request.

"To the extent Lilly personnel may have participated in this program, Lilly apologizes to those patients affected by it," said spokeswoman Debbie Davis. "We are investigating this matter vigorously and if company policies were violated, Lilly will take appropriate action."

The FDA - which regulates prescription medicines, their makers and their marketing - is monitoring the case to see whether it needs to intervene.

"Although the acts of prescribing and providing the drug likely come under state jurisdiction, FDA intends to keep an eye on this case because of the promotion issues it may raise," said spokesman Larry Bachorik.

The Broward County, Fla., woman, identified in court documents only as S.K., this week sued her doctors, Walgreens and Lilly, charging invasion of privacy and improper medical practice.

"Dear Patient," reads a letter accompanying the pills that was signed by her local doctors. "We are very excited to be able to offer you a more convenient way to take your antidepressant medication.

"For your convenience, enclosed you will find a FREE one-month trial of Prozac Weekly," the letter continues, before cautioning patients to stop their regular antidepressant one day before starting the once-a-week version.

"It really upset me," S.K. said in a telephone interview arranged by one of her attorneys, Stephen Sheller of Philadelphia.

She said her grandchildren might have opened and swallowed the mailed drug, and anyone seeing her mail would learn she had depression, which she keeps private. "Then I started to think, 'Wait a minute, how did they know to send them to me?"'

S.K. said her doctor maintains the office physicians signed a blank form letter provided by a Lilly salesman. S.K.'s medical records show no Prozac prescription, said fellow attorney Gary Farmer Jr. of Fort Lauderdale.

Representatives for the doctors' office, Holy Cross Medical Group, did not return calls seeking comment.

The lawsuit charges that Walgreens must have allowed access to patient prescription records, providing Lilly with a list of antidepressant users. S.K. said she tried Prozac once years ago - the prescription was filled by a Walgreens in Massachusetts, she contends - but had a bad side effect and switched to a competing drug that she has used ever since.

Walgreens didn't allow anyone access to patient records and properly filled prescriptions from doctors' offices for all the Prozac it mailed, said Michael Polzin from the chain's Deerfield, Ill., headquarters.

He wouldn't say how many samples Walgreens mailed, or how much the Lilly coupons reimbursed the pharmacy for the drugs. A month's supply of Prozac Weekly costs about $63 wholesale.

"How would we know the patient didn't know the prescription was coming?" Polzin asked.

Copyright 2002 The Associated Press. All rights reserved.