A medication for severe inflammatory spinal arthritis will cost about $40 instead of $1,300 when it is subsidised by the federal government from December.

A medication for treating severe inflammatory spinal arthritis will soon be subsidised by the federal government, bringing the cost of filling a script down from more than $1300 to less than $40.

Simponi will be listed on the Pharmaceutical Benefits Scheme, meaning it will be subsidised by the government, from December 1.

But those who need the medication most won't have to wait until December to get it cheaper, under immediate compassion measures.

The change is expected to save those experiencing inflammatory spinal arthritis up to $15,000 a year.

Those with the condition, technically known as non-radiographic axial spondyloarthritis, experience back pain, fatigue, stiffness and immobility of the joints.

The damage it causes is progressive and irreversible, with patients at risk of spinal fractures and permanent damage to spinal mobility and function.

Simponi helps reduce inflammation and joint destruction for some, through changes to the patient's immune system.

"This listing will save families thousands of dollars and help patients manage their condition and improve their quality of life," Health Minister Greg Hunt said.