Why We Can Compound

Why 503A Compounding Pharmacies Are Allowed to Compound Drugs: Legal Rights, FDA Rules & Medical Justification

In an increasingly standardized pharmaceutical world, compounding pharmacies serve an essential role: formulating customized medications that meet specific patient needs. But what exactly allows a compounding pharmacy to legally compound a drug? The answer lies in a mix of federal regulations, medical necessity exemptions, and drug shortages. In this article, we’ll break down the FDA’s regulatory framework: 503A pharmacies, Category 1/2/3 drugs, the “Green List,” Purple Book, and more. The hope is to give physicians clarity on the why and how behind compounded medications.

What It Means to Be a 503A Compounding Pharmacy

As a 503A compounding pharmacy, Mountain View Pharmacy operates under a traditional, patient-centered model, compounding medications only in response to valid, individualized prescriptions. This practice is governed by Section 503A of the Federal Food, Drug, and Cosmetic Act (FDCA), clarified under the Drug Quality and Security Act (DQSA) of 2013.

Key Features of 503A Pharmacies:
- Must compound only after receiving a valid, patient-specific prescription.
- Are licensed by the state Board of Pharmacy, not registered as FDA manufacturers.
- Are exempt from Current Good Manufacturing Practice (CGMP) requirements, though must comply with USP standards such as <795>, <797>, and <800>.
- Cannot compound biologics (e.g., insulin, vaccines).
- Are subject to state-level oversight, but may face FDA action for unsafe or noncompliant practices.

This structure ensures personalized medication preparation while maintaining regulatory safeguards at the state and federal levels.

Source: FDA - Compounding and the FDA: Questions and Answers

Section 503A of the Federal Food, Drug, and Cosmetic Act

Section 503A of the FDCA exempts traditional compounding pharmacies from certain FDA requirements—such as New Drug Approval (NDA), Current Good Manufacturing Practices (CGMPs), and labeling—when specific criteria are met.

Key Reference: FDA Guidance on Section 503A

✔ A 503A Pharmacy Must:

• Compound only in response to a valid prescription for an identified individual patient.

• Use bulk drug substances that are either:

  • Components of FDA-approved drugs, or

  • On the 503A Category 1 Bulk Drug List established by the FDA.

• Avoid compounding drugs that are “essentially copies” of commercially available drugs, unless there's a valid medical need.

Medical Necessity: The Physician’s Role

Compounding a drug that is an essential copy of an FDA-approved product is generally not allowed unless the prescribing physician provides a clinical rationale.

This means that:

“The compounded drug is necessary for the patient because of a change in ingredient, dosage form, allergen removal, or another valid medical reason.”

FDA Source: Guidance for Industry: Compounded Drug Products That Are Essentially Copies
https://www.fda.gov/media/94329/download

This protects patients and ensures that compounding serves unique clinical needs. Each patient is treated as an individual, with curated, customized care.

“Essentially Copies” Rule

A compounded drug is “essentially a copy” of a commercial product if:

• It has the same active ingredients, strength, dosage form, AND route of administration,

• Unless the prescriber documents a clinical difference needed by the patient.

This requirement prevents pharmacies from undermining the commercial drug market while preserving access for patients with specific or special medical needs.

Compounding During FDA-Recognized Drug Shortages

When an FDA-approved drug is unavailable due to shortage, a 503A pharmacy may compound it even if it would normally be considered a commercial copy.

FDA Drug Shortage Database: https://www.accessdata.fda.gov/scripts/drugshortages/

“The FDA does not intend to take action if a 503A pharmacy compounds a drug that is essentially a copy of a drug on the shortage list, provided the drug remains unavailable.”

What Can a 503A Pharmacy Compound?

Category 1 Bulk Substance List – Accepted for Compounding

Category 1 substances may be used in compounding by 503A pharmacies. These substances meet key criteria such as having a USP monograph, being components of FDA-approved drugs, or having a documented history of use. Pharmacies using Category 1 ingredients must ensure proper sourcing and documentation.

Category 2 – Do Not Use – Safety Concerns or Insufficient Data

Category 2 substances are not permitted for use in compounding due to known or suspected safety issues, such as toxicity, carcinogenicity, or adverse events. These drugs have failed preliminary FDA evaluation or lack the safety evidence required for patient use. Prescribing or compounding with Category 2 ingredients may result in regulatory action.

Category 3 – Not Allowed for Compounding – No Safety Concerns

Category 3 substances have insufficient information for the FDA to determine their safety, efficacy, or medical utility. While these ingredients may not present known harm, they lack credible evidence to support their use as effective components in compounded drugs. As a result, they are not permitted for compounding, since there's no substantiated benefit or clinical justification for their inclusion in patient therapy.

FDA Source: 503A Bulk Drug Substances – Categories Explained (Federal Register)

What is the FDA “Purple Book”?

The Purple Book applies to biologics and biosimilars. 503A pharmacies cannot compound biologics, as they are subject to different FDA regulations (e.g., insulin, vaccines, monoclonals).

What Is the FDA “Green List”?

In September 2025, the FDA launched a “Green List” import alert system to protect the public from illegally imported GLP-1 active pharmaceutical ingredients (APIs), like semaglutide and tirzepatide, that are being used in some compounded drugs.

This Green List is now an official FDA tool that:

• Identifies foreign API manufacturers that have been inspected or evaluated by the FDA and found to meet U.S. quality and compliance standards.

• Allows only those approved APIs into the country for potential use in compounded medications.

• Blocks or detains APIs from unverified sources at the border without physical examination.

• Source: FDA Press Release – Green List for GLP-1 APIs

Why This Matters for Providers

Due to the surge in demand for compounded GLP-1 drugs for diabetes and weight management, some pharmacies may seek to source semaglutide or tirzepatide APIs from unapproved overseas facilities. This has led to:

• Adverse events, including hospitalizations,

• Use of unapproved salt forms or incorrect dosing,

• Increased risk to patient safety.

By establishing the Green List, the FDA aims to:

• Ensure that any compounded versions of GLP-1 drugs (when legally permitted) use only high-quality, FDA-reviewed ingredients,

• Prevent dangerous or ineffective drug formulations from reaching patients.

FDA’s Concerns with Unapproved GLP-1 Drugs

Mountain View’s approach, since the beginning

At Mountain View Pharmacy, we prioritize patient safety and regulatory compliance in every aspect of our compounding practice, starting with ingredient sourcing. By adhering to this standard, we align with the FDA’s mission to prevent unsafe or adulterated drugs from entering the U.S. market and ensure that your patients receive compounded medications made from the highest quality, legally sourced ingredients. Since the beginning of our sterile compounding journey, we have only sourced ingredients from Green Listed drug manufacturers.

Are Compounded Drugs FDA-Approved? Not Exactly—Here's What That Means

One important clarification for providers:

Each compounded prescription is not individually FDA-approved.

Unlike commercially manufactured drugs, which undergo the FDA's new drug application (NDA) process, compounded medications are made on a patient-specific basis and therefore fall outside of traditional FDA approval pathways.

That doesn’t mean they’re unsafe or unregulated.

Here's what it does mean:

• The formulated product (i.e., your patient’s compounded cream, capsule, solution, or injection) has not gone through clinical trials or NDA review.

• However, 503A pharmacies must still follow strict professional standards, including:

  • USP <795> and USP <797> (for non-sterile and sterile compounding)

  • Use of USP-grade ingredients and quality-verified suppliers

  • Following internal standard operating procedures (SOPs)

  • Rigorous documentation, batch records, and patient-specific logs

  • Ongoing training and competency evaluations for compounding staff

Compounded ≠ Unregulated

While 503A pharmacies are exempt from some FDA manufacturing regulations (like CGMP), they are regulated at the state level by Boards of Pharmacy and are expected to:

• Follow USP compounding standards

• Comply with state pharmacy law

• Pass routine inspections

• Document and report adverse events if they occur

Key Reference: USP Compounding Standards Overview
FDA: Compounding and the FDA – What Providers Need to Know

The Takeaway for Providers

When you prescribe a compounded medication:

• You are not prescribing an FDA-approved drug, but

• You are prescribing a medication made according to nationally recognized standards, with patient safety as the guiding principle.

By ensuring your prescriptions clearly state the clinical rationale, you support both regulatory compliance and optimal patient care.

The Mountain View Difference

As a provider, you deserve a compounding partner who protects both your license and your patients. At Mountain View Pharmacy, we don’t just meet regulatory expectations — we exceed them. That commitment is reflected in every prescription we prepare.

We go beyond industry standards by submitting every batch of our sterile compounds for third-party testing, ensuring your patients receive exactly what you prescribed. Our dedication to transparency, safety, and quality is unwavering. We aim to earn your trust by consistently delivering high-quality, patient-specific medications that are both effective and compliant.

For Prescribers: How to Support Legal Compounding

To help ensure compliance, your prescription must include:

• The patient's full name

• The specific medication and formulation requested

• A note stating:
  “This formulation is medically necessary because [e.g., patient needs specific dosing / needs non-standard strength / patient allergic to dye in commercial product / requires liquid form, etc.].”

 FDA References Used

1. FDA (2020). Guidance for Industry: Compounded Drug Products That Are Essentially Copies of Approved Drug Products Under Section 503A.

2. FDA (2016). Bulk Drug Substances That Can Be Used to Compound Drug Products in Accordance With Section 503A.

3. FDA (2023). Drug Shortages Database.

4. FDA (2021). Compounding and the FDA: Questions and Answers.

5. FDA (2022). Pharmacy Compounding of Human Drug Products Under Section 503A of the Federal Food, Drug, and Cosmetic Act.