Any patient requesting the fatal medication would have to make two oral requests, 15 days apart, and submit a written request witnessed by two people, including one person who is not a relative, heir, attending doctor, or connected with a health facility where the requester lives.

Critics say assisted suicide laws could exploit depressed or vulnerable people who worry they've become a burden on their families.

"This is not an issue of choice and keeping government out of end-of-life issues," said Chris Carlson, chairman of the Coalition Against Assisted Suicide. "It is a matter of injecting government more into end-of-life issues, and it raises serious questions about who will do the choosing."

Those who support I-1000 say it's a humane choice for those who feel they have no other option.

"The people who choose the law really want to live and have likely been through chemo or surgeries, and now it's to the point where they can no longer choose life," said Arline Hinckley, a social worker who has worked with terminally ill patients and is working with the Yes on I-1000 campaign. "I think the person who can't choose life should have the right to chose the kind of death they want."

Forty-nine people died under the terms of the law last year, according to a report by the Oregon Department of Human Services. Since it went into effect, more than 340 patients have used the law to end their lives.

Most suffered from cancer, and the most common end-of-life reasons they expressed were loss of autonomy, loss of dignity and a decreasing ability to participate in activities they enjoyed.