The future of cheaper medicines and 60-day dispensing is again up in the air, with the Senate likely to consider a push to scrap the change.

The federal opposition initially sought to move a disallowance motion overturning the Labor government policy in the Senate on Thursday.

But Liberal and Nationals senators decided to seek to defer the vote.

However, Labor received the backing of crossbenchers - including David Pocock, Lidia Thorpe and Jacqui Lambie - to stop the motion being deferred, which could lead to a vote occurring on Thursday.

At that stage, Labor expects the disallowance motion will be voted down.

The coalition supports 60-day dispensing and cheaper medicines, but is against the government's approach, arguing pharmacies would face closures and might need to lay off staff to cover costs due to lost income.

Under the changes, about six million Australians can expect to see their costs halved for 320 common medicines.

The pharmacy sector has been fiercely lobbying against the shift from the existing 30-day limit, arguing it will lead to significant financial losses for the industry.

The nation's doctors have hit back, saying the changes will make medicines more affordable for patients and will free up clogged GP clinics by reducing the frequency of repeat visits.

Australian Medical Association president Steve Robson said the coalition had the opportunity to implement the same measures when it was in government, but instead chose to kill the plan.

"It's time that people in the Senate overall took the opportunity to make medicines affordable at a time of cost-of-living crisis," he told reporters in Canberra.

Royal Australian College of General Practitioners president Nicole Higgins said the policy was recommended to government more than five years ago, but the coalition "folded under pressure from the pharmacy owners".

"We're calling on the Senate to put patients before profit," she said.

Health Minister Mark Butler said the government was determined to make medicines cheaper, dismissing criticism that the policy had been rushed.

He said the government had fruitful discussions with the crossbench ahead of the vote being delayed.