OTTAWA -- The federal government's controversial bill on assisted dying sailed through the House of Commons on Tuesday, approved by a vote of 186-137.

"It's an historic day," Health Minister Jane Philpott said immediately following the vote, thanking MPs for passing a bill she said "will essentially transform end-of-life care options for Canadians."

Only four Liberal MPs -- including Rob Oliphant, the chair of a special joint parliamentary committee that had recommended a much more permissive approach to assisted dying -- voted against Bill C-14, as did most Conservatives, all New Democrat and Bloc Quebecois MPs and Green Leader Elizabeth May.

But the bill now heads into choppier waters in the Senate, where the government has less control over the agenda and many independent-minded senators are pushing for amendments.

It is virtually guaranteed the bill will not be passed by Monday, the day the ban on assisted dying is formally lifted in accordance with last year's landmark Supreme Court ruling.

"No, no, impossible," Sen. Claude Carignan, Conservative leader in the Senate.

Senators are not dragging their feet; they've agreed to extend their sitting hours and have taken the usual step of inviting Justice Minister Jody Wilson-Raybould and Philpott to testify about the bill before the entire Senate on Wednesday.

However, they must still debate the bill at second reading, send it to committee to hear from some half a dozen witnesses, propose and consider possible amendments and debate and vote on the bill a final time.

Carignan said more than 40 Conservative senators want to speak during second reading debate alone and he expects "many amendments" will be proposed. Consequently, he said the bill can't be put to a final vote until the end of next week at the earliest, possibly sometime the following week.

Advocates of assisted dying are urging senators to scrap the bill's restrictive eligibility criteria. Without that change "Bill C-14 will be constitutionally dead on arrival," said Shanaaz Gokool, CEO of Dying with Dignity Canada.

"(That's) a warning the Liberal government has chosen to ignore. We encourage members of the Senate not to make the same mistake."

However, a number of disability rights advocates are urging passage of the bill, despite their concerns that it doesn't go far enough to protect the vulnerable. They argued that an imperfect bill is better than no legislation at all.

That continued to be the message from Wilson-Raybould and Philpott as they kept up the pressure Tuesday to have the bill enacted by June 6.

In the absence of a new law, the Supreme Court's criteria for allowing assisted dying would apply. But Wilson-Raybould suggested that would amount to "one of, if not the broadest assisted dying regimes in the world."

"Under an approach where any serious medical condition is eligible, the law would be saying that an assisted death could be an acceptable treatment for a soldier with post-traumatic stress disorder, a young person who suffered a spinal cord injury in an accident or a survivor whose mind is haunted by memories of sexual abuse," she said.

Wilson-Raybould also argued there is uncertainty whether the court's criteria would have "the legal effect of completely striking down existing criminal law that prohibits consensual killing and the aiding of suicides outside of an assisted dying context." She did not explain that assertion.

In what's known as the Carter decision, the Supreme Court ruled that consenting adults have a right to seek medical help to end their lives if they have "grievous and irremediable" medical conditions that are causing enduring suffering that they deem intolerable.

Bill C-14 sets out considerably more restrictive eligibility criteria, allowing assisted dying only for clearly consenting adults "in an advanced stage of irreversible decline" from a serious and incurable disease, illness or disability and for whom natural death is "reasonably foreseeable."

Jocelyn Downie, a professor in both the medicine and law faculties at Dalhousie University, said Wilson-Raybould is misrepresenting the Supreme Court ruling.

The court said the medical condition must be irremediable, while PTSD and memories of sexual abuse "may well be remediable," Downie said. Moreover, she said a young person's initial response in the days or even months following a spinal cord injury would not be considered "enduring" suffering, as the court required.

"To suggest that somehow the sky is going to fall on June 6 is specious," agreed NDP justice critic Murray Rankin, noting that medical regulators in every provinces have issued strict guidelines doctors must follow in providing assistance in dying.

Unless it's amended by the Senate, Rankin predicted the bill will face court challenges and be found unconstitutional.

"People who won that hard-fought victory in Carter are going to be back in the Supreme Court in a few months. That's wrong," he said.