New Haven, CT—Benzoyl peroxide (BPO) acne drugs on pharmacy shelves lack stability and can degrade into carcinogenic benzene, according to a new study.

The researchers reporting in the Journal of Investigative Dermatology tested 111 products from major U.S. retailers and found unacceptably high levels of benzene at room temperature and benzene formation with heat and UV light, according to their study.

The Yale University School of Medicine–led researchers explained that degradation of the products and formation of benzene appear to occur when sitting on shelves at room temperature, at elevated temperatures, and when exposed to ultraviolet (UV) levels representative of sunlight. The researchers added that drug stabilization techniques like encapsulation do not appear to prevent the formation of benzene in BPO drug products.

The degradation appeared to occur most rapidly when the products were exposed to UV light at outdoor levels, which is a concern because the products are often used by consumers over extended periods of time. The authors pointed out that there is no safe level or duration of exposure to benzene.

“The potential degradation of BPO into benzene has been a topic of concern in dermatology. Our research demonstrates that BPO products can generate benzene at typical room and store shelf temperatures, while cold storage significantly reduces this formation,” explained coinvestigator Christopher G. Bunick, MD, PhD, of the Department of Dermatology and program in Translational Biomedicine, Yale University School of Medicine. “These findings suggest a need to recommend refrigeration of BPO products throughout the supply chain—from manufacturing to patient use—to limit benzene exposure. Until formulations are developed to prevent benzene formation, refrigeration may serve as a practical solution to minimize unnecessary exposure.”

Dr. Bunick also urged in a press release that healthcare professionals advise patients on the appropriate use of BPO, including potential risks associated with UV exposure.

BPO is a diacyl peroxide with bactericidal activity used in topical drug products up to 10% concentration available through prescription or OTC for the treatment of acne and rosacea. The authors noted that acne drug products can also be formulated as a combination of drug products including BPO. Among the product types are wash-away cleansers and topical creams, gels, and lotions that are left on the skin for long periods.

The researchers used mass spectrometry methods to detect benzene in 111 new, unopened products stored at room temperature on shelves of major U.S. retailers and the air surrounding them with and without UV exposure. They say it is the first time BPO drug products have been shown to degrade into benzene via a mechanism other than heat and that benzene formation can occur independently of the starting benzene concentration in new or cold temperature–stored BPO drug products.

Lead investigator David Light, cofounder and president of Valisure, LLC, New Haven, Connecticut, and affiliate professor at Long Island University, Connecticut, added, “The discovery of benzene formation in benzoyl peroxide acne treatments presents a potentially serious public health risk. Our research demonstrates that these products, widely used by consumers of all ages, can potentially contain or generate concerningly high levels of benzene, particularly under common environmental conditions. This issue highlights the critical importance of rigorous independent testing of drug products to help protect consumers from harmful contaminants or degradation products.”

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