It’s a matter of time. Dermatologists who compound a local anesthetic mixture of lidocaine plus epinephrine in their offices often have to watch the clock, discarding any unused product after 4 hours per US Pharmacopeia (USP) <797> standards. However, a new study provides evidence that suggests this timeframe could be extended up to 24 hours at room temperature and up to 7 days under proper refrigeration.

Testing of buffered lidocaine with epinephrine showed multiple lots met criteria for safety, sterility, and potency. Researchers led by Seemal R. Desai, MD, checked samples for purity, pH levels, particulate matter, endotoxin limits, antimicrobial effectiveness, and integrity of container closures. The study was published online on February 9, 2026, in the Journal of the American Academy of Dermatology.

The 4-hour limit under USP <797> “applies to immediate-use compounded sterile preparations. That limit is not specific to buffered lidocaine,” said Desai, who is founder and medical director of Innovative Dermatology in Plano, Texas, and immediate past president of the American Academy of Dermatology (AAD).

“Rather, it reflects a conservative, risk-based framework designed to minimize microbial contamination when sterile products are manipulated outside of controlled cleanroom environments,” Desai added.

The study was born through years of extensive discussion and via a USP collaboration with the FDA, CDC, and leading dermatology societies (the AAD Association [AADA], American College of Mohs Surgery, American Society for Dermatologic Surgery, and the American Society for Mohs Surgery) to create a new evidence-based monograph for buffered lidocaine that could extend beyond the current 4-hour standard.

“Our work does not challenge the rationale for patient safety. Instead, it provides validated stability and sterility data for a very common dermatologic preparation so that standards can be evidence-based rather than purely precautionary,” said Desai, who is also a clinical associate professor in the Department of Dermatology at the University of Texas Southwestern Medical Center in Dallas.

A Boost to Compounding Confidence

Desai believes the findings and upcoming monograph will help dermatologists feel more comfortable compounding their own lidocaine plus epinephrine anesthetic. “This study does not relax safety standards,” he said. In contrast, he told Medscape Medical News, “It strengthens them by providing validated analytical testing, evidence-based beyond-use dating, defined storage requirements, and clarification of proper container closure methods.”

In addition, Desai said, “This offers a data-driven framework rather than a purely precautionary time limitation” for those practices with segregated compounding areas.

Comprehensive Testing

For the study, Desai, co-authors, and members of the Compounding Work Group tested the purity and potency of the lots using high-performance liquid chromatography. To assess stability, researchers tested three lots of buffered lidocaine (9.6 mg/mL) and epinephrine (9.6 mcg/mL) injection in 3 mL syringes at regular intervals over 7 days.

They checked one lot for particulates, sterility, and endotoxin levels and two additional lots for antimicrobial preservative effectiveness. At a 95% CI, investigators found pH was stable within 0.5 points and potency within 10% under both study conditions at 7 days.

The 95% CI dropped below 90% for the epinephrine component at room temperature at approximately 48 hours, so researchers chose the conservative 24-hour cutoff. Similarly, they noted that with refrigeration, “while remaining safe and stable, buffered lidocaine begins to lose its vasoconstrictive efficacy after 7 days and should be administered by then.”

“It was reassuring that sterility, endotoxin levels, particulate matter, and antimicrobial effectiveness all met specifications when preparations were compounded using appropriate aseptic technique,” Desai noted.

There is a caveat. Dermatologists should use their personal and professional judgment when interpreting and applying the study findings, Desai said. “Ultimately, clinicians must be aware of and comply with all applicable state, federal, and regulatory guidance that governs their specific practice location and setting, as requirements may vary by jurisdiction.”

The Bigger Picture

The challenge of the 4-hour USP <797> standard is not unique to dermatology. Buffered lidocaine with epinephrine is widely used in plastic surgery, otolaryngology, ophthalmology, oral surgery, emergency medicine, and podiatry.

The study serves as a model framework for office-based providers who want to validate analytical methods, conduct stability and sterility testing, apply regression analysis for beyond-use dating assignment, and evaluate container closure integrity, Desai said. “The broader goal is not deregulation, but data-driven regulation that supports patient safety, access to care, and operational practicality.” In addition, this study represents a landmark effort by the dermatology specialty as a whole and will likely be a model for other specialties in the future, he said.

From Insight to Action

The next step, incorporation of the study findings into a future monograph, depends on expert review and consideration of comments collected during a public review period.

There are two parallel pathways, Desai said. If adopted, the USP monograph would establish a standardized formulation, compounding method, testing parameters, and assigned beyond-use dating based on validated data. “That provides a formal mechanism within the USP framework to move beyond the default 4-hour limit.”

The second pathway is education and guidance on implementation. Clinicians should follow USP <797>, FDA sanitary guidance, and relevant specialty society recommendations, Desai said. Providers can also refer to the Joint Position Statement on Safe In-Office Preparation of Buffered Lidocaine as a Local Anesthetic for further direction.

Asked to comment on the study, Brett Coldiron, MD, dermatologist and Mohs surgeon at the Skin Cancer Center in Cincinnati, said, “This is important because it allows for dermatologists to safely compound their own medications….This is the first beachhead, as it were, to regain our autonomy in practicing medicine.”

“This is what we have always done and is what is best for our patients,” added Coldiron, who is a member of the Compounding Work Group.

Desai disclosed having received funding for independent laboratory testing provided jointly by major dermatology societies. No commercial pharmaceutical company funded the study. Two co-authors disclosed serving on the USP Compounding Expert Committee but not representing USP in this investigation. The remaining authors reported having no conflicts of interest related to this study. Desai disclosed serving in multiple dermatology leadership roles, including most recently as AAD president and previously as chair of the AADA Compounding Workgroup. He also disclosed serving on the FDA Pharmacy Compounding Advisory Committee and serving as a consultant and/or investigator for many pharmaceutical and industry companies. Coldiron reported having no relevant financial disclosures.

Damian McNamara is a freelance contributor to Medscape Medical News. He worked full-time for Medscape and WebMD from 2018 to 2024. Damian has a BA in chemistry and an MA in science, health, and environmental reporting/journalism. He works out of a home office in Miami, with a 100-lb chocolate lab known to snore under his desk during work hours.