The demands from Sprout’s investors are another problem for the embattled drugmaker. Valeant, whose stock has declined more than 85 percent since its peak in August, is struggling to cut costs, fix underperforming businesses and pay down a debt that ballooned to more than $30 billion. The Laval, Quebec-based company, which has delayed filing its annual report pending an internal investigation, also needs to reset a strategy after its business practices came under scrutiny, and is looking for a new chief executive officer to replace Mike Pearson.

The investor group, represented by Boies Schiller & Flexner LLP managing partner Jonathan Schiller, received cash in the acquisition, but they stand to collect royalty payments if the drug is successful. They are requesting that Valeant provide all “books, contracts, documents and records” related to the development and commercialization of Addyi by April 13, according to the letter.

“The Sprout shareholders have a contractual right to obtain the information that we have requested of Valeant,” Schiller said by e-mail. “They also have legal remedies under the merger agreement to pursue claims against Valeant for its failure to perform its obligations.”

Sprout is one of four business lines that have performed poorly and need fixing, Pearson told senior managers this month. The struggling unit has started to cut jobs and eliminated the positions of its two national sales directors, according to people familiar with the matter, who asked not to be identified because the moves aren’t public. In addition, about 12 regional sales directors have been asked to interview for their jobs, the people said.

At the time of the merger agreement in August -- within days of its approval by the U.S. Food and Drug Administration -- both parties expected Addyi to hit $1 billion in net sales in the first full seven quarters following its introduction, the investors said in their letter.

By December, Pearson told investors in a meeting that 2016 sales expectations were in the range of $100 million to $150 million. On March 15, after the letter was sent, Pearson told analysts on a conference call that Valeant had cut that forecast “significantly,” without giving more details.

“Valeant remains strongly committed to Addyi and to ensuring that it remains affordable and accessible to premenopausal women who have been waiting for a medical treatment option,” Little, the company spokeswoman, said in her e-mail. “We continue to work closely with pharmacists, health-care providers, and patients to educate them about Addyi.”

One of Sprout’s investors before Valeant acquired the company was Bill Ackman, the billionaire who runs Pershing Square Capital Management LP. Pershing Square is one of Valeant’s top three shareholders, according to filings; Ackman this month gained a seat on the company’s board and has promised to help turn around the drugmaker. He took a less then 1.5 percent stake in Sprout during a fundraising round, a person familiar with the matter said last year. He declined to comment on the letter.

Addyi has been been struggling in part because the mail-order pharmacy that could have helped distribute the drug, Philidor Rx Services, is now out of the picture following a scandal that forced Valeant to sever the relationship in October. Insurers are denying or limiting coverage for the daily pill, and large pharmaceuticals benefit managers have been blocking it.

Addyi sales are growing after a difficult start, Anne Whitaker, company group chairman, said on a March 15 conference call. About 57 percent of prescriptions written are now being filled and paid for, up from 25 percent to 30 percent in the fourth quarter, she said.

The treatment, which was rejected twice before getting approved, carries a boxed warning, the FDA’s strictest, and women have to sign an agreement acknowledging the risks.

In their letter, the Sprout investors said Valeant failed to comply with its obligation to educate patients and physicians about the product. Valeant was obligated to spend at least $200 million over six quarters starting in January to advertise it in print or television, develop disease-awareness campaigns and make educational materials, among other things, they said.

“Letters like that are designed to get a response and suggest that there may be litigation,” said Charles Elson, director of the John L. Weinberg Center for Corporate Governance at the University of Delaware. “It will go on for a while. These things stretch on for a few years.”