Health experts are calling the case of two doctors arrested last week on suspicion of assisting in the death of a 51-year-old woman with ALS "fundamentally different" from past euthanasia cases that led to other doctors' convictions for murder in Japan, because she allegedly asked them to kill her for money on Twitter.

Yoshikazu Okubo, who operates a clinic in Natori, Miyagi Prefecture, and Naoki Yamamoto, a doctor in Tokyo, allegedly administered a lethal dose of barbiturates to Yuri Hayashi at her home in the western Japan city of Kyoto on Nov. 30 with her consent, investigative sources said.

Short-acting barbiturates, such as pentobarbital, taken in large dosages cause death by respiratory arrest and are known to be used by groups that assist with suicides in Europe and the United States.

Hayashi's disease, amyotrophic lateral sclerosis, also known as Lou Gehrig's disease, causes gradual paralysis with no fundamental treatments established.

According to the sources, neither Okubo, 42, nor Yamamoto, 43, were the woman's attending physician, and the ALS patient and Okubo are believed to have exchanged messages using the social networking service for nearly a year prior to her death.

It was Hayashi who offered 1.3 million yen ($12,400) for the job, nearly the same amount charged by a Swiss group for assisting suicides.