The letter on Friday asked for “clear answers” to what procedures are in place to “ensure that advisory committee members are properly vetted,” among other questions.

The Academies told The Times that beginning in 2019 Sackler family donations were no longer used for science-related events, research and awards, the purposes for which they were intended. The funds “were never used to support any advisory activities on the use of opioids,” Megan Lowry, a spokeswoman, said.

The donations amounted to roughly $19 million and, as invested funds in the institution’s endowment, were worth about $31 million in late 2021, the most recent accounting available. Universities that accepted Sackler funds, including Tufts and Brown, have reallocated some of the money to addiction prevention and treatment efforts.

Members of the Sackler family who were active in running Purdue Pharma began donating in 2008 to the National Academies of Sciences. The money was used to sponsor forums and studies.

In 2015, family members donated $10 million to launch the Raymond and Beverly Sackler Prize in Convergence Research, according to reports by the organization’s treasurer. Dr. and Ms. Sackler died in 2017 and 2019. An attorney for the family said those donations had “nothing at all to do with pain, medications or anything related to the company.”