UPDATE 1-Insys posts bigger loss amid bribery probe of founder

(Adds details on Subsys, probe)

Nov 2 (Reuters) - Insys Therapeutics on Thursday posted a quarterly loss that was bigger than analysts' expectations, as it faced soft demand for its flagship opioid painkiller Subsys, which is at the center of a federal probe at the company.

Insys's billionaire founder John Kapoor was arrested on charges that he participated in a scheme to bribe doctors to prescribe Subsys. Kapoor, also Insys's majority shareholder, resigned from the company's board on Sunday.

Shares of the Arizona-based drugmaker are down 45 percent since the beginning of the year.

The company said on Sunday it recorded $150 million as its "best estimate of the minimum liability" to settle a U.S. Department of Justice investigation into Subsys.

Subsys is an under-the-tongue spray for cancer patients that contains fentanyl, an addictive opioid painkiller, and is at the center of allegations against the company over its marketing practices for the drug.

Insys reported a net loss of $166.3 million or $2.30 per share in the third quarter ended Sept. 30, compared to a net income of $2.9 million or 4 cents per share, a year earlier.

Excluding one-time items, Insys lost 21 cents per share. Analysts on average had expected a loss of 16 cents, according to Thomson Reuters I/B/E/S.

Net revenue fell to $30.7 million from $57.8 million. (Reporting by Manas Mishra in Bengaluru; Editing by Sai Sachin Ravikumar)