(Reuters) - McKesson Corp’s shareholders voted against the company’s executive pay policy, following a campaign that criticized the drug wholesaler for its role in the U.S. opioid drug epidemic.

Three U.S. state treasurers and the International Brotherhood of Teamsters campaigned against McKesson’s pay practices and urged it to appoint an independent chairman.

“The Compensation Committee will conduct a thorough review of the current executive compensation plan and consider implementing changes that further drive alignment between incentives and shareholder value,” McKesson said on Wednesday.

The company also said it would split the role of chairman and CEO in the future, commencing with its next CEO.

Shareholders Teamsters and state treasurers from Illinois, Pennsylvania and West Virginia urged McKesson to take stringent efforts to combat the opioid epidemic plaguing the country.

Opioid drugs, including prescription painkillers and heroin, killed more than 33,000 people in 2015, according to the Centers for Disease Control and Prevention (CDC), and have led to widespread regulatory and federal response.

Another bone of contention for shareholders was McKesson Chief Executive John Hammergren’s compensation.

Hammergren was paid more than $20 million for the year ended March 31, despite a record $150 million settlement that McKesson paid to resolve a U.S. probe into whether it failed to report suspicious orders of addictive painkillers.

Teamsters said on Wednesday the change in policy would hopefully provide greater oversight and accountability for how prescription drugs are distributed in the United States.

“This shareholder vote should serve as a wake-up call to AmerisourceBergen, Cardinal Health and other companies involved in the manufacturing or distribution of prescription opioids.”

McKesson and rivals AmerisourceBergen Corp and Cardinal Health have been sued by several West Virginia counties for failing to report suspicious orders of opioids.

Shares of McKesson, which is due to report its quarterly results on Thursday, were down 1 percent at $165.80 in afternoon trading on Wednesday.