WARNING LETTER
Medical Products Laboratories, Inc.
MARCS-CMS 721916 —
April 09, 2026
Delivery Method:
VIA UPS
Product:
Drugs
Recipient:
Recipient Name
Mr. Elliot Stone
Recipient Title
President/CEO
Medical Products Laboratories, Inc.
9990 Global Road
Philadelphia
,
PA
19115
United States
Issuing Office:
Center for Drug Evaluation and Research (CDER)
United States
Warning Letter
320-26-61
April 9, 2026
Dear Mr. Stone:
The United States Food and Drug Administration (FDA) inspected your drug manufacturing facility, Medical Products Laboratories, Inc., FEI 2513595, at 9990 Global Road, Philadelphia, from September 29 to October 16, 2025.
This warning letter summarizes significant violations of Current Good Manufacturing Practice (CGMP) regulations for finished pharmaceuticals. See Title 21 Code of Federal Regulations (CFR), parts 210 and 211 (21 CFR parts 210 and 211).
Because your methods, facilities, or controls for manufacturing, processing, packing, or holding do not conform to CGMP, your drug products are adulterated within the meaning of section 501(a)(2)(B) of the Federal Food, Drug, and Cosmetic Act (FD&C Act), 21 U.S.C. 351(a)(2)(B).
Your firm manufactures and is responsible for introducing or delivering for introduction into interstate commerce in the United States products that are unapproved new drugs in violation of sections 301(d) and 505(a) of the FD&C Act, 21 U.S.C. Sections 331(d) and 355(a), including but not limited to: Hydro-Q 4% Gel (hydroquinone 4%); Sodium Sulfacetamide 8% and Sulfur 4% Topical Suspension; Sodium Sulfacetamide 9% and Sulfur 4% Wash; Sodium Sulfacetamide 9.8% Shampoo; Sodium Sulfacetamide 9.8% and Sulfur 4.8% Cleanser; Sodium Sulfacetamide 9.8% and Sulfur 4.8% Lotion; Sodium Sulfacetamide 9.8% and Sulfur 4.8% Cream; Sodium Sulfacetamide 10% and Sulfur 5% Cleanser; Sodium Sulfacetamide 10% Wash; Salicylic Acid 28.5% Solution; Plexion Shampoo (sodium sulfacetamide 9.8%); Plexion Lotion (sodium sulfacetamide 9.8% and sulfur 4.8%), Plexion Cream (sodium sulfacetamide 9.8% and sulfur 4.8%) as prescription drug products. Based on our review, these products are unapproved new drugs under section 505(a) of the FD&C Act, 21 U.S.C. Section 355(a). As explained further below, introducing or delivering these products for introduction into interstate commerce violates sections 301(d) and 505(a) of the FD&C Act, 21 U.S.C. Sections 331(d) and 355(a).
We reviewed your November 6, 2025 response to our Form FDA 483 in detail and acknowledge receipt of your subsequent correspondence.
During our inspection, our investigators observed specific violations including, but not limited to, the following.
CGMP Violations
1. Your firm failed to establish and follow appropriate written procedures, designed to prevent objectionable microorganisms in drug products not required to be sterile (21 CFR 211.113(a)).
Microbiological Results in Finished Drug Product and
(b)(4)
Samples
Your firm manufactures prescription and over-the-counter (OTC) drug products for
(b)(4)
administration. You failed to adequately establish and follow procedures to prevent contamination with objectionable microorganisms. For example, you used an unvalidated
(b)(4)
treatment protocol on filled drug product batches in an attempt to reduce microbiological content. Your laboratory reported gross microbiological contamination on plates for both total aerobic microbiological count (TAMC) and total yeast and mold count (TYMC) tests in the following non-sterile finished drug products for
(b)(4)
administration:
(b)(4)
lot
(b)(4)
(TAMC: too numerous to count (TNTC) and TYMC: TNTC)
(b)(4)
lot
(b)(4)
(TAMC: TNTC and TYMC: TNTC)
(b)(4)
lot
(b)(4)
(TAMC: TNTC and TYMC:
(b)(4)
colony forming units (CFU) per gram)
Your investigation of the failing results in
(b)(4)
lot
(b)(4)
concluded that contamination was from the
(b)(4)
component, recovered from a mixture of this component with
(b)(4)
. However, your investigation failed to consider out-of-limit (OOL) microbiological recoveries from your
(b)(4)
system.
You subsequently released drug products based on results from
(b)(4)
treatment resampling. Your corrective action and preventive action (CAPA) in response to the microbiological contamination included revising the drug product formulation to increase
(b)(4)
content.
(b)(4)
are not a substitute for a comprehensive approach to preventing objectionable microorganisms from contaminating your drug products and cannot be relied on to reduce in-process bioburden during manufacturing.
We note that on
(b)(4)
, you issued a voluntary recall of
(b)(4)
, lots
(b)(4)
, due to microbiological contamination.
Your response commits to revising your procedures to no longer allow
(b)(4)
treatment to rework batches after failing microbiological results and to place a reworked batch on real-time stability. You also include a risk assessment which concludes there is no health risk for two failing lots. Your response is inadequate in that your risk assessment does not extend to all drug products where
(b)(4)
treatment was attempted, nor does your response provide your plans for addressing product quality and patient safety risks for lots on which you used
(b)(4)
treatment or product you released after failing microbiological results. Moreover, your response does not address whether additional bacterial species were present, nor did you provide evidence supporting your claims that growth on total yeast and mold plates was solely bacterial.
This adverse pattern of microbiological contamination in your drug products demonstrates a significant failure to adhere to CGMP. Unresolved manufacturing and quality problems can pose a significant hazard to patients.
In response to this letter, provide:
A comprehensive, independent assessment of the design and control of your firm’s manufacturing operations, with a detailed and thorough review of all microbiological hazards.
A detailed risk assessment addressing the hazards posed by distributing drug products with potentially objectionable contamination. Specify actions you will take in response to the risk assessment, such as customer notifications and product recalls.
Complete investigations into all batches with potential objectionable microbiological contamination or a failing microbiological result (whether or not later invalidated). The investigations should detail your findings regarding the root causes of the contamination.
Appropriate microbiological batch release specifications (i.e., total counts, identification of bioburden to detect objectionable microbes) for each of your drug products.
A summary of results from testing retain samples of all drug product batches of which you have received failing, out-of-specification (OOS), OOL or out-of-trend (OOT) microbiological test results. Also provide test results of retains during periods when your
(b)(4)
system was not operating under a state of control. You should test microbiological quality (total counts and identification of bioburden to detect any objectionable microbes) of each batch. If testing yields any failing, OOS or OOL result, indicate the corrective actions you will take, including notifying customers and initiating recalls.
A comprehensive remediation plan for the design, control, and maintenance of the
(b)(4)
system.
o Provide a comprehensive evaluation of vulnerabilities of
(b)(4)
system design and control, and summarize all deficiencies found in the system. The summary should, at minimum, describe various system characteristics that were assessed for adequacy (system temperature, materials of construction, slope, any identified dead-legs, any stagnant locations, any unsanitary fittings, flow velocity, etc.)
Your total microbiological count limits to monitor whether this system is producing
(b)(4)
suitable for the intended uses for each of your products.
A detailed risk assessment addressing the potential effects of the observed
(b)(4)
system failures on the quality of all drug product lots currently within expiry. Specify actions that you will take in response to the risk assessment, such as customer notifications and product recalls.
2. Your firm failed to establish adequate written procedures for production and process control designed to assure that the drug products you manufacture have the identity, strength, quality, and purity they purport or are represented to possess (21 CFR 211.100(a)).
You failed to adequately validate your manufacturing processes to demonstrate that your processes are reproducible and controlled to consistently yield drug products of uniform character and quality. For example, you used a process qualification study performed at a different facility to manufacture and release
(b)(4)
. You could not provide evidence your processes (e.g. equipment, components, and manufacturing conditions) were comparable between your facility and the site where initial process validation was performed.
Additionally, you failed to adequately validate your process for manufacturing
(b)(4)
. While a process validation study for this product had been initiated, it included insufficient data. At the direction of your customer, you discontinued your efforts to complete process validation for this product, yet you continued manufacturing batches for commercial distribution.
In your response, you discuss a retrospective review of
(b)(4)
batches within expiry. You also indicate that you have paused production of
(b)(4)
until process validation activities can be completed. You also state that you have updated your process validation procedure and that you have verified that process validation studies have been conducted for drug products you manufacture. Your response is inadequate in that you did not evaluate the implications of changes made to product formulations for drug products that you manufacture.
Process validation evaluates the soundness of design and state of control of a process throughout its lifecycle. Each significant stage of a manufacturing process must be designed appropriately and assure the quality of raw material inputs, in-process materials, and finished drugs. Process qualification studies include intensive monitoring and testing throughout each significant process stage to characterize intra-batch variation and evaluate batches to determine whether an initial state of control has been established.
Successful process qualification studies are necessary before commercial distribution. Thereafter, ongoing vigilant oversight of process performance and product quality is necessary to ensure you maintain a stable manufacturing operation throughout the product lifecycle.
In response to this letter, provide:
A detailed summary of your validation program for ensuring a state of control throughout the product lifecycle, along with associated procedures. Describe your program for process performance qualification (PPQ), and ongoing monitoring of both intra-batch and inter-batch variation to ensure a continuing state of control.
A timeline for performing appropriate PPQ for each of your marketed drug products which lack appropriate studies. Also include an explanation how you will ensure proper satisfactory PPQ studies are performed prior to future distribution of any drug products.
A risk assessment for the distributed drug products produced without performing any process validation studies or using inadequately validated processes.
Process performance protocol(s), and written procedures for qualification of equipment and facilities.
A detailed program, including your procedure, for designing, validating, maintaining, controlling and monitoring each of your manufacturing processes that includes vigilant monitoring of intra-batch and inter-batch variation to ensure an ongoing state of control. Also, include your program for qualification of your equipment and facility.
3. Your firm failed to thoroughly investigate any unexplained discrepancy or failure of a batch or any of its components to meet any of its specifications, whether or not the batch has already been distributed (21 CFR 211.192).
Finished Drug Product Microbiological Testing
Your firm failed to adequately investigate failing microbiological results in finished products. For example, your
(b)(4)
lot
(b)(4)
obtained a failing result of
(b)(4)
CFU/g for TYMC (specification ≤
(b)(4)
CFU/g). After your contract testing laboratory failed to identify the fungal species, you concluded, without evidence, that contamination occurred “during handling, transportation and/or testing.” You invalidated this failing result based on results of resampling and released the lot.
Microbiological contamination may not be uniformly distributed. A product sample may not be representative of the type or level of contamination within the batch. Further, testing the final product for microbiological contamination does not ensure that you have appropriate controls in place to ensure product quality. As a manufacturer, you have a responsibility to fully investigate unexplained discrepancies, deviations, and failures to assess their impact on product quality.
Stability Assay
Your firm failed to conduct adequate investigations into OOS stability results. For example, in two separate incidents, you invalidated OOS stability results for subpotent assay without adequate scientific justification. You relied on resampling data from
(b)(4)
, lots
(b)(4)
, to invalidate the initial stability OOS result with no identified laboratory error or rationale.
Complaint Investigations
You did not adequately investigate complaints you received. For example, upon receiving complaints of product crystallization in
(b)(4)
, you concluded that this crystallization was due to “transportation and/or storage” during winter months. Your investigation failed to consider changes made to the formulation or the status of process validation activities for the formulation.
In your response, you commit to reopening complaints of crystallization and discoloration of
(b)(4)
while pausing manufacturing of this product. You also commit to revising your complaint and investigation procedures, but you did not provide revised procedures. Your response also fails to perform a retrospective review of invalidated OOS results or discuss improperly invalidated results for drug products which remain on the market.
Inadequate investigations can lead to unidentified root causes, ineffective CAPA, and recurring problems that compromise the ability to manufacture safe and effective drug products.
In response to this letter, provide:
A comprehensive, independent assessment of your overall system for investigating deviations, discrepancies, complaints, OOS results, and failures. Provide a detailed action plan to remediate this system. Your action plan should include, but not be limited to, significant improvements in investigation competencies, scope determination, root cause evaluation, CAPA effectiveness, quality unit oversight, and written procedures. Address how your firm will ensure all phases of investigations are appropriately conducted.
A retrospective, independent review of all invalidated failing/OOS (including in-process and release/stability testing) results for U.S. products currently in the U.S. market and within expiry as of the date of this letter and a report summarizing the findings of the analysis, including the following for each OOS:
o Determine whether the scientific justification and evidence relating to the invalidated failing/OOS results conclusively or inconclusively demonstrates causative laboratory error.
o For investigations that conclusively establish laboratory root cause, provide rationale and ensure that all other laboratory methods vulnerable to the same or similar root cause are identified for remediation.
o For all failing/OOS results found by the retrospective review to have an inconclusive or no root cause identified in the laboratory, include a thorough review of production (e.g., batch manufacturing records, adequacy of the manufacturing steps, suitability of equipment/facilities, variability of raw materials, process capability, deviation history, complaint history, batch failure history). Provide a summary of potential manufacturing root causes for each investigation, and any manufacturing operation improvements.
A comprehensive review and remediation plan for your failing/OOS result investigation systems. The CAPA should include but not be limited to addressing the following:
o Quality unit oversight of laboratory investigations
o Identification of adverse laboratory control trends
o Resolution of causes of laboratory variation
o Initiation of thorough investigations of potential manufacturing causes whenever a laboratory cause cannot be conclusively identified
o Adequately scoping of each investigation and its CAPA
o Revised failing/OOS investigation procedures with these and other remediations
4. Your firm failed to establish and follow an adequate written testing program designed to assess the stability characteristics of drug products and to use results of stability testing to determine appropriate storage conditions and expiration dates (21 CFR 211.166(a)).
Your stability program was not adequate to ensure that the drug products you manufacture, maintain their identity, strength, quality, purity, and safety throughout their shelf lives. For example, your stability study for
(b)(4)
concluded that a
(b)(4)
expiration is supported at a temperature of
(b)(4)
to
(b)(4)
degrees Celsius (
(b)(4)
to
(b)(4)
degrees Fahrenheit). However, your firm labeled much wider storage conditions as
(b)(4)
to
(b)(4)
degrees Fahrenheit at the instruction of your customer, without adequate data to support the wider labeled storage conditions. We note that you reduced the range of the labeled temperature limits, but they were still outside the range of your stability data.
In your response, you committed to revising the stability protocol for this product and placing future lots on stability. You also state that you “can no longer rely on written justifications from product owners to deviate from the general [C]GMP requirements.” Your response is inadequate in that you do not include a comprehensive review of your stability program, nor do you provide your revised stability protocol. Additionally, your response does not describe a retrospective review of batches which lack adequate stability data to support labeled expiration dates and storage conditions.
Without the appropriate stability studies, you do not have adequate scientific evidence to support that your drug product retains its quality attributes throughout the labeled
(b)(4)
expiry period.
In response to this letter, provide:
A comprehensive, independent assessment and CAPA plan to ensure the adequacy of your stability program. Your remediated program should include, but not be limited to:
o Stability indicating methods
o Stability studies for each drug product in its marketed container-closure system before distribution is permitted
o An ongoing program in which representative batches of each product are added each year to the program to determine if the shelf-life claim remains valid
o A detailed definition of the specific attributes to be tested at each station (timepoint)
o All procedures that describe these and other elements of your remediated stability program.
Unapproved New Drug Violations
Your firm’s products are drugs as defined by section 201(g)(1) of the FD&C Act, 21 U.S.C. Section 321(g)(1), because they are intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease and/or intended to affect the structure or any function of the body.
Examples from your product labeling that provide evidence of the intended use (as defined in 21 CFR 201.128) of these products as drugs include, but may not be limited to, the following:
Hydro-Q Gel (hydroquinone 4%)
Indicated for the gradual bleaching of hyperpigmented skin conditions such as chloasma, melasma, freckles, senile lentigines and areas of melanin hyperpigmentation.
Plexion Shampoo (sodium sulfacetamide 9.8%)
Intended for topical application in the following scaling dermatoses: seborrheic dermatitis and seborrhea sicca (dandruff).
Plexion Cream and Plexion Lotion (sodium sulfacetamide 9.8%, sulfur 4.8%)
Indicated for use in the topical control of acne vulgaris, acne rosacea and seborrheic dermatitis.
Sodium Sulfacetamide 9.8% Shampoo
Intended for topical application in the following scaling dermatoses: seborrheic dermatitis and seborrhea sicca (dandruff).
Sodium Sulfacetamide 10% Wash
Indicated for topical application in the following scaling dermatoses: seborrheic dermatitis and seborrhea sicca (dandruff). It also is indicated for the treatment of secondary bacterial infections of the skin due to organisms susceptible to sulfonamides.
Sodium Sulfacetamide 9.8% and Sulfur 4.8% Cream, Cleanser, and Lotion
Indicated for use in the topical control of acne vulgaris, acne rosacea and seborrheic dermatitis.
Sodium Sulfacetamide 8% and Sulfur 4% Topical Suspension
Indicated for use in the topical control of acne vulgaris, acne rosacea and seborrheic dermatitis.
Sodium Sulfacetamide 9% and Sulfur 4% Wash
Indicated for use in the topical control of acne vulgaris, acne rosacea and seborrheic dermatitis.
Sodium Sulfacetamide 10% and Sulfur 5% Cleanser
Indicated for use in the topical control of acne vulgaris, acne rosacea and seborrheic dermatitis.
Salicylic Acid 28.5% Solution
Indicated for the topical treatment and removal of common warts and plantar warts.
Your products are “new drugs” under section 201(p) of the FD&C Act, 21 U.S.C. 321(p), because they are not generally recognized as safe and effective (GRASE) for use under the above-described conditions prescribed, recommended, or suggested in their labeling.
With certain exceptions not applicable here, a new drug may not be introduced or delivered for introduction into interstate commerce without an approved application from FDA in effect, as described in section 505(a) of the FD&C Act, 21 U.S.C. 355(a). No approved applications pursuant to section 505 of the FD&C Act, 21 U.S.C. 355, are in effect for these products.
Accordingly, these products are unapproved new drugs. The introduction or delivery for introduction into interstate commerce of these unapproved new drug products violates sections 301(d) and 505(a) of the FD&C Act, 21 U.S.C. 331(d) and 355(a).
Responsibilities as a Contractor
Drugs must be manufactured in conformance with CGMP. FDA is aware that many drug manufacturers use independent contractors such as production facilities, testing laboratories, packagers, and labelers. FDA regards contractors as extensions of the manufacturer.
You and your customer
(b)(4)
, have a quality agreement regarding the manufacture of
(b)(4)
. You are responsible for the quality of drugs you produce as a contract facility regardless of agreements in place with product owners. You are required to ensure that drugs are made in accordance with section 501(a)(2)(B) of the FD&C Act for safety, identity, strength, quality, and purity. See FDA’s guidance document Contract Manufacturing Arrangements for Drugs: Quality Agreements at https://www.fda.gov/media/86193/download.
Quality Systems
Your firm’s quality systems are inadequate. For guidance on establishing and maintaining CGMP-compliant quality systems, see FDA’s guidances:
Q8(R2) Pharmaceutical Development
at https://www.fda.gov/media/71535/download,
Q9(R1) Quality Risk Management
at https://www.fda.gov/media/167721/download and
Q10 Pharmaceutical Quality System
at https://www.fda.gov/media/71553/download.
Consultant Recommended
Based upon the nature of the violations we identified at your firm, you should engage a consultant qualified as set forth in 21 CFR 211.34 to evaluate your operations and to assist your firm in meeting CGMP requirements. The qualified consultant should also perform a comprehensive six-system audit of your entire operation for CGMP compliance and evaluate the completion and efficacy of your corrective actions and preventive actions before you pursue resolution of your firm’s compliance status with FDA.
Conclusion
The violations cited in this letter are not intended to be an all-inclusive list of violations that exist at your facility. You are responsible for investigating and determining the causes of any violations and for preventing their recurrence or the occurrence of other violations.
Correct any violations promptly. Failure to promptly and adequately address this matter may result in regulatory or legal action without further notice including, without limitation, seizure and injunction. Unresolved violations may also prevent other Federal agencies from awarding contracts.
Failure to address violations may also cause FDA to withhold issuance of Export Certificates. FDA may withhold approval of new applications or supplements listing your firm as a drug manufacturer until any violations are completely addressed and we confirm your compliance with CGMP. We may re-inspect to verify that you have completed corrective actions to address any violations.
FDA requests that you contact CDER's Drug Shortages Staff immediately at drugshortages@fda.hhs.gov so that we can work with you to meet any obligations you may have to report discontinuances or interruptions in your drug manufacture, as required under 21 U.S.C.§ 356c(a), and to allow FDA to consider, as soon as possible, what actions, if any, may be needed to avoid shortages and protect the health of patients who use your products.
This letter notifies you of our findings and provides you an opportunity to address the above deficiencies. After you receive this letter, respond to this office in writing within 15 working days
1
. Specify what you have done to address any violations and to prevent their recurrence. In response to this letter, you may provide additional information for our consideration as we continue to assess your activities and practices. If you cannot complete corrective actions within 15 working days, state your reasons for delay and your schedule for completion.
Send your electronic reply to CDER-OC-OMQ-Communications@fda.hhs.gov. Identify your response with FEI 2513595 and ATTN: Andrew Haack.
Sincerely,
/S/
Francis Godwin
Director
Office of Manufacturing Quality
Office of Compliance
Center for Drug Evaluation and Research
/S/
Tina Smith
Captain, U.S. Public Health Service
Director
Office of Unapproved Drugs & Labeling Compliance
Office of Compliance
Center for Drug Evaluation and Research
_________________
1
Under program enhancements for the Generic Drug User Fee Amendments (GDUFA) reauthorization for fiscal years (FYs) 2023-2027, also known as the GDUFA III Commitment Letter, your facility may be eligible for a Post-Warning Letter Meeting to obtain preliminary feedback from FDA on the adequacy and completeness of your corrective action plans.
Content current as of:
04/14/2026
Regulated Product(s)
Drugs