Sunday's test of an emergency system for delivering medication to Twin Cities households via the U.S. mail went off without obvious hitches, but it'll take time to assess it for less obvious problems and barriers, a spokesman for the Minnesota Department of Health said Sunday evening.

Operation Medicine Delivery was the first full-scale test of a strategy for distributing medicine in the event of, for instance, an epidemic or large-scale anthrax attack. About 300 mail carriers delivered a simulated supply of the antibiotic doxycycline in the form of an empty pill bottle to 37,000 residential addresses in four metro-area ZIP codes -- 55101, 55102, 55411 and 55422, which include parts of St. Paul, north Minneapolis, Robbinsdale, Crystal and Golden Valley.

"We're very pleased with how the field portion of this test went," said Buddy Ferguson, spokesman for the state Health Department. All deliveries, which began early in the morning, were completed by 3:30 p.m., he said.

"We think this will be a very promising option in the event of an emergency" that requires medication distribution, he said. "But there are lots of moving parts to it, and still lots of things yet to assess, lots of people, including law enforcement, to talk to about potential barriers that might be out there." A complete assessment will take days or weeks, he said.

Operation Medicine Delivery, funded by the U.S. Department of Health and Human Services as part of its national emergency response planning efforts, was pilot-tested in Boston, Philadelphia and Seattle, but the Twin Cities' test was the first one conducted on a broad scale.

Residents who received the empty pill bottles can simply recycle them, officials said.

PAMELA MILLER