URBANA — The maker of a commonly used drug treatment for people with multiple sclerosis says it will cover the hospitalization costs of any Health Alliance Medical Plan member who sticks to the treatment regimen and has a severe relapse.

The drug company, Bayer HealthCare, said its agreement with Health Alliance in Urbana represents the first time it has entered into such a contract with an insurer.

Bayer is the maker of Betaseron, an injectable drug intended for patients with relapsing-remitting multiple sclerosis, the most common form of MS, an autoimmune disease affecting the central nervous system.

Betaseron, a brand name for interferon beta-1B, is intended to reduce the frequency of relapses.

An average hospitalization for an MS patient with a severe relapse runs $12,000, the company said.

Bayer offers a program to help patients get started and remain on the medication, and said its agreement with Health Alliance reinforces its belief that when patients stick to the treatment plan, their chances for a better clinical outcome improve.

About 400,000 people in the U.S. have MS, and about 75 to 85 percent of everyone with the disease is initially diagnosed with relapsing-remitting MS, according to the National Multiple Sclerosis Society.

Dr. Robert Parker, Health Alliance's chief medical officer, said this isn't the first time Health Alliance has sought an agreement with a drug company to stand behind the success of a costly treatment for its members.

Health Alliance formerly had a similar agreement with the maker of an osteoporosis drug, he said.

Members are assumed to be complying with treatment as prescribed if Health Alliance is receiving regular pharmacy claims for the medication, Parker said.

Bayer spokeswoman JoAnne Marlin said Bayer is in discussions with other insurers to negotiate similar agreements.