BANGOR – Some of the 15 church members treated in what may be the largest acute arsenic poisoning case on record have been sent home, and the rest are expected to be discharged within weeks, if not days.

But even out of the hospital, they will continue to take medication to drive any lingering arsenic out of their bodies and will undergo frequent monitoring of heart, kidney and liver functions. And they will be advised not to eat shellfish or flounder, cod and other groundfish.

Because arsenic poisoning is so rare, the poisonings from tainted coffee at the Gustaf Adolph Evangelical Lutheran Church in New Sweden provide a unique opportunity for doctors to study and to record what works, and what doesn’t, to help future victims.

“I’ve heard this called the largest mass poisoning with arsenic, or perhaps the largest mass poisoning in the United States, in many, many years,” said Dr. Anthony Tomassoni, director of the Northern New England Poison Center in Portland, who has been involved daily.

The patients range in age from about 30 to 70. A 16th patient, who was 78, died within hours of being stricken. Investigators deemed his death a homicide and said a church member who committed suicide five days later was at least partially responsible.

The seven sickest patients remain at Eastern Maine Medical Center in Bangor, where their conditions were upgraded this week – three from critical to serious and four from serious to fair.

Doctors trying to determine when to let them go home must look at several factors, said Dr. Erik Steele, the hospital’s vice president for patient care.

Because they must be able to take medications by mouth, patients with lingering nausea would have to remain in the hospital, he said. Vital organs such as heart, lungs and kidneys must be functioning reasonably well, and patients should have some support at home.

The main reason for keeping patients in the hospital now is to monitor them for heart arrhythmia, or irregular heartbeat. The heart must be closely monitored because arrhythmia can lead to cardiac arrest.

In the days after they are discharged, patients will need daily electrocardiograms, Tomassoni said.

Doctors will keep close tabs on their overall health and will monitor their arsenic levels. Patients cannot eat shellfish or groundfish because they contain minute amounts of arsenic that could skew routine testing.

While confidentiality rules bar doctors from referring to specific cases or providing detailed accounts, they say they are pleased with how patients responded to treatment.

All but one of the eight patients at Cary Medical Center in Caribou, where church members began showing up soon after leaving the April 27 coffee hour, were discharged this week.

For the most part, patients should be able to return to work and pursue their normal routines, Tomassoni said, although they may want to avoid particularly strenuous activities until their EKG readings stabilize.

“No doubt there’s going to be some social and emotional consequences. This is an exposure that happened in a very close-knit group in a very small community,” he said.

As for long-term physical effects, doctors acknowledge there is much they don’t know.

“Any patient who has had a substantial arsenic poisoning faces an uncertain risk of long-term complications,” Steele said. “You won’t know until you get there.”

Tomassoni said studies of the long-term impact of arsenic generally focus on exposure to low levels in drinking water over years and even decades. There are no studies of the long-term effects of a single high exposure, he said, but New Sweden is likely to shed some light on that question.

Steele considers it an obligation.

“There are so few cases that doctors have a duty to share the information they have so that the next patient gains some of that benefit,” he said.