A Drug Master File (DMF) is a submission to the FDA that may be used to provide confidential, detailed information about facilities, processes, or articles used in the manufacturing, processing, packaging, and storing of drugs. DMFs are not required by law or regulation — they are voluntary submissions that drug substance (API) manufacturers, packaging component manufacturers, and other suppliers use to share proprietary information with the FDA without disclosing it to their customers. For foreign API manufacturers, a DMF is often a critical component of doing business with US drug manufacturers and distributors, because it allows the API manufacturer to support their customers' drug applications (NDAs, ANDAs, or OTC monograph listings) without revealing trade secrets to those customers.
Types of Drug Master Files
The FDA recognizes five types of DMFs, although Type II is by far the most common for foreign API manufacturers. Type I DMFs (Manufacturing Site, Facilities, Operating Procedures, and Personnel) were discontinued by the FDA in 2000 — this information is now included in drug applications directly. Type II DMFs cover Drug Substance, Drug Substance Intermediate, and Material Used in Their Preparation, or Drug Product — this is the type that foreign API manufacturers typically file. Type III DMFs cover Packaging Material. Type IV DMFs cover Excipients, Colorants, Flavors, Essences, or Materials Used in Their Preparation. Type V DMFs cover FDA-Accepted Reference Information. Of these, Type II DMFs are the most widely used and the most relevant to foreign API manufacturers seeking to supply the US pharmaceutical market.
What a Type II DMF must contain
A Type II DMF for a drug substance (API) must contain comprehensive information about the drug substance including its nomenclature, description, and chemical structure; the manufacturing process (including detailed descriptions of synthetic steps, purification procedures, and process controls); specifications and analytical methods for the drug substance, including tests for identity, purity, potency, and impurities; stability data demonstrating the drug substance's stability under specified storage conditions; and information about the packaging and labeling of the drug substance. The DMF must also include information about the manufacturing facility, including its location, layout, equipment, and quality systems. The level of detail required is comparable to what would be included in the Chemistry, Manufacturing, and Controls (CMC) section of an NDA or ANDA.
How DMF authorization letters work
A DMF by itself does not receive FDA approval — the FDA does not independently review or approve DMFs. Instead, a DMF is reviewed only when it is referenced by a drug application (NDA, ANDA, or IND) or another submission. When a drug manufacturer wants to use an API from a DMF holder, the DMF holder issues a Letter of Authorization (LOA) to the drug manufacturer, granting permission to reference the DMF in their application. The drug manufacturer then references the DMF in their application, and the FDA reviews the relevant portions of the DMF as part of the overall application review. This mechanism allows the API manufacturer to maintain the confidentiality of its manufacturing process while enabling its customers to demonstrate to the FDA that their drug product uses a well-characterized, quality-controlled drug substance.
DMF submission process
DMFs are submitted electronically to the FDA through the Electronic Common Technical Document (eCTD) gateway or by direct electronic submission to FDA's DMF mailbox. The submission must be in eCTD format for Type II DMFs related to drug substances. The initial submission includes the complete DMF content, and subsequent amendments are filed to update information such as manufacturing process changes, specification revisions, stability data updates, or facility changes. DMF holders must also submit annual reports to the FDA confirming that the DMF information is current, and must notify the FDA and all authorized references if the DMF is closed or if significant changes are made to the drug substance or manufacturing process.
Common issues with foreign DMF submissions
Foreign API manufacturers frequently encounter issues with DMF submissions including incomplete manufacturing process descriptions, insufficient impurity characterization (the FDA expects thorough identification and control of all process-related and degradation impurities), inadequate stability data (the FDA expects stability studies conducted under ICH guidelines with appropriate storage conditions and time points), and poorly organized submissions that make FDA review difficult. Additionally, foreign API manufacturers must register their drug establishment with the FDA under 21 CFR Part 207 — a DMF does not substitute for establishment registration, and an unregistered establishment's products will be detained at the border regardless of whether a DMF has been filed.
How FDABridge supports API manufacturers
FDABridge provides drug establishment registration and US Agent services for foreign API manufacturers. While DMF preparation requires specialized pharmaceutical regulatory expertise, FDABridge ensures that your facility registration — the administrative prerequisite for all FDA interactions — is current and accurate. Visit fdabridge.com/drug to see our drug registration services or fdabridge.com/contact to discuss your compliance needs.
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