The FDA issued a warning letter to United Exchange Corp. for serious quality violations, including using products from “multiple sub-standard contract manufacturers” at its Cypress and Rialto drug manufacturing plants.

The agency inspected the two facilities from April 2 to 6, 2018, and found that they did not properly monitor contract manufacturers and used multiple CMOs that the agency had previously cited for good manufacturing practice violations.

“Your firm lacks a robust quality system and enabled the introduction of adulterated drug products into the U.S. market,” the agency said.

The two facilities lacked proper procedures for handling deviations, investigations and specification failures by their contractors. The agency reminded the company that it treats contractors as “extensions of the manufacturer” and said the drugmaker is responsible for the quality of its drugs “regardless of agreements” with contract facilities.