Amphastar Pharmaceuticals, Inc. announced that its subsidiary, International Medication Systems, Limited, received an FDA Warning Letter regarding current Good Manufacturing Practice violations at its South El Monte, California facility. The FDA cited issues with investigation procedures, environmental monitoring, and manufacturing equipment following a December 2025 inspection. The company is implementing a remediation plan and evaluating the impact on operations, though it cannot guarantee FDA satisfaction with the response. Amphastar Pharmaceuticals, Inc. is a pharmaceutical company that develops and manufactures generic and specialty injectable drugs.