A Senate committee passed legislation that will allow doctors in Maryland to prescribe a lethal dose of medicine to terminally ill patients who want to end their lives, clearing a hurdle for the bill to advance to the Senate floor this week.

But advocates of a national aid-in-dying movement complained that amendments to the Maryland legislation “will make it nearly impossible for patients to access.”

The Senate Judicial Proceedings Committee voted 8 to 3, largely along party lines Friday, to allow the bill to move to the full Senate. Sen. Chris West (Baltimore County) was the only Republican on the panel to vote for the bill.

The committee made significant changes to the bill that were aimed at preventing possible coercion and removing immunity from doctors who participate in the end-of-life option. Advocates say the amendments go too far and hinted at the possibility of withdrawing support for the measure if it remains in its current form.

Sen. William C. Smith Jr. (D-Montgomery), the lead sponsor in the Senate, said he thought the bill “struck a balance between the protections and the access.”

“It was the committee’s will to err on the side of extreme caution,” he said. “I still think it’s a significant step forward and it does represent progress.”

Maryland Sen. William C. Smith Jr. (D-Montgomery) at a pre-session Democratic legislative luncheon in Annapolis in January. (Linda Davidson/The Washington Post)

Kim Callinan, the chief executive of Compassion & Choices, which has led efforts across the country to pass similar legislation, said the Senate version of the bill adds roadblocks not present in any other state. Aid-in-dying laws have been enacted in the District, California, Colorado, Hawaii, Montana, Oregon, Vermont and Washington state.

“It does a disservice when the experience that [terminally ill patients] have is roadblocks,” Callinan said. “All the things that they did in this bill will just further deter doctors from practicing and put more barriers in place for dying patients.”

The House version of the bill, which passed after an emotional debate earlier this month, is modeled after Oregon’s law and would apply to terminally ill people whose doctors say they have less than six months to live. A patient would have to make three requests, both oral and written, to end his or her life, with waiting periods and the ability to rescind the request at any time.

Lawmakers amended the bill late Thursday during a seven-hour discussion in which they went over the 23-page bill line by line and, in some instances, word by word.

The committee considered more than 50 amendments and approved 20.

Among the most controversial ­changes are a requirement that the attending doctor and the consulting doctor are not in the same practice; a mandatory mental health referral from a psychiatrist, psychologist or licensed clinical social worker; a definition of terminal illness that includes descriptions like irreversible and progressive; removal of legal immunity for participating doctors; and a requirement that a consulting physician provide the patient with a list of alternative treatments in writing.

Opponents of the bill say the state is going down a slippery slope, one that could lead to poor and vulnerable patients being pressured into a premature death.

Joseph Marine, an associate professor at the School of Medicine at Johns Hopkins University and a member of the Maryland Against Physician Assisted Suicide coalition, said he considers the bill “fatally flawed.”

“This bill strikes at the heart of the medical principle that we do not cause the death of a patient,” he said.

Sen. Jeff Waldstreicher (D-Montgomery), who voted for the bill, said that he didn’t agree with all of the changes the committee made but that he thought they would help ensure the bill passed this session.

“I think it makes it a tighter bill,” he said. “It also makes it politically palatable on the floor of the Senate.”

Waldstreicher said he did not see the amendments as “dealing a fatal blow” to access. He said if access turns out to be too limited, the legislature could revisit the issue. He said the General Assembly made a similar move after it initially approved a medical marijuana bill that was too restrictive.

In other action, the Senate gave initial approval to a bill that would abolish the state’s handgun review board, replacing the citizen-run panel with administrative law judges.

The panel, which decides whether to overturn a denial from the Maryland State Police for a permit to carry a handgun, has come under scrutiny in recent years for increasingly overturning denials for handgun permits. The bill has not been considered by the House.

The Senate also advanced legislation that would allow people to register to vote at the polls on Election Day. That bill has already passed the House.