SAN DIEGO >> At least 504 terminally ill Californians have requested a prescription for life-ending drugs since a state law allowing doctor-assisted deaths went into effect in June 2016, marking the first publicly released data on how the practice is playing out in the nation’s most populous state.

The number released Thursday represents only those who have contacted Compassion & Choices, an advocacy group that provides information on the process. The organization believes the overall figure to be much higher. State officials have not released data yet.

How the new law is used in California could provide a window into what would happen if the practice spreads nationwide. Some see providing the choice to the dying as a logical evolution in a medical care system advanced in helping people live longer but limited in preventing slow, painful deaths.

Critics say they are concerned that the option will lead to hasty decisions, misdiagnosis and waning support for palliative care, in which dying people can be sedated to relieve suffering.

Betsy Davis was among the first Californians to use the law. The 41-year-old artist with ALS, or Lou Gehrig’s disease, held a party to say goodbye to her family and friends before taking the lethal dose of drugs July 24.

Her sister, Kelly Davis, said the family has no regrets about her decision.

“It’s only strengthened my belief in the law,” Kelly Davis said. “Sometimes I think about where she would have been in the progression of the illness at this point. Would she be on a breathing machine? Would she be able to eat? I think the answer would be yes to the breathing machine, and no to the eating.

“I think how much it would have broken my heart to see her suffering. The fact she had that option, she embraced that option, it gave her back a sense of control,” Davis said.

Oregon was the first state to adopt such a law in 1997. It reported 204 people received life-ending prescriptions last year, and of those, 133 people died from ingesting the drugs, including 19 recipients from prior years. Most were older than 65 and had cancer.

Doctor-assisted deaths are also legal in Colorado, Montana, Vermont, Washington state and Washington D.C.

Under California’s law, which marks its anniversary June 9, patients must be given six months or less to live, make two verbal requests within 15 days of each other and submit a written request.

“We won’t have the full picture until the state releases its data about how many people have utilized the law, but we have enough evidence to show it is working remarkably well in a state with 10 times Oregon’s population,” said Matt Whitaker, Compassion & Choices’ California director.

“The personal stories of the people who have utilized the law show it has provided comfort and relief from intolerable suffering, just as the state Legislature intended it to do,” he said.

The group says 498 health care facilities and 104 hospice centers in California have adopted policies to allow for such prescriptions. More than 80 percent of insurance companies in the state also cover the cost of the drugs, the group said.

Sherry Minor called the law her 80-year-old husband’s “greatest relief.” Retired psychologist John Minor took the lethal drugs in Sept. 15 to end his suffering from terminal lung disease. He wrote two weeks before dying that even morphine was not enough for the intense pain.

“It was such a miracle the law passed,” said Minor, 79, of Manhattan Beach, outside Los Angeles. “He was so incredibly lucky in that way. It was important for us to know that he go the way he wanted to go.”

The law passed in California after 29-year-old Brittany Maynard, who was dying from brain cancer, had to move to Oregon in 2014 so she could end her life.

Her husband said Maynard would be happy to see others like her don’t have to leave her home state to get relief.

“Like Brittany, these terminally ill Californians didn’t want to die — but they were dying — and just wanted the option to die peacefully,” Dan Diaz said in a statement.

The California law is being challenged by the Life Legal Defense Foundation, American Academy of Medical Ethics and several physicians who say determining when someone has six months or less to live is an arbitrary decision that opens the door for abuse. A hearing is scheduled for June 16.