Triclosan Again in the Crosshairs
By Bob Roth
In a conference presentation published by S.B. Levy in 2001 (Antibacterial household products: cause for concern. Emerg Infec Dis 7, supple 3, 512-515), risks were noted associated with the hundreds of available commercial products that contain antibacterial agents. The principal focus of the presentation was the risk of developing resistance to biocides such as triclosan and the potential that such resistance could cross over to the arena of antibiotics. However, a subsequent industry-supported white paper concluded that such risks were low, citing considerable experimental data and expert panel considerations. FDA’s consumer health review in 2010 of triclosan efficacy and safety stated that there was insufficient data to conclude that triclosan was hazardous to humans, but that evaluation would be ongoing.
Most recently a new potential risk of triclosan has been noted, i.e., that of acute muscle toxicity (Cherednichenko et al. 2012. PNAS 109:14158-63). Findings of altered hemodynamics in mice, decreased swimming performance in minnows, and in vitro adverse effects on muscle cells in the laboratory were all documented. Of course, the exposures to triclosan that elicited the adverse effects were extremely large in comparison to human exposures from topical solutions, toothpastes, and other consumer products. Expected uptake and delivery of triclosan from topical application sites to heart and skeletal muscle under consumer product use conditions is likely to be quite limited, and the link between the observed nonclinical effects and actual human risks would seem tenuous.
Should consumers and regulators be alarmed by the recent muscle toxicity data? Common sense suggests that real-life systemic toxicity risks from commercial products containing triclosan must be extremely low, though ongoing safety surveillance is indicated and perhaps some human safety pharmacology investigation warranted. But this does remind us of the earlier potential risk of emerging antimicrobial resistance, and whether we should re-direct our focus back to the unresolved issue of potential cross-resistance or co-resistance between antibacterials such as triclosan and therapeutic antibiotics. Unlike the rather remote chance that triclosan appreciably interacts with muscle cells, triclosan has ample opportunity to interact with clinically relevant cutaneous and oropharyngeal bacteria. The recent findings of an association between the selection of triclosan-resistant strains of important pathogens such as Salmonella enterica typhimurium and decreased sensitivity to critical antibiotics such as ciprofloxacin (Birosova and Milulasova, 2009. J Med Micro 58:436-441) would suggest our attention belongs in this arena.
Bob Roth is Vice President and Worldwide Medical Director at The Weinberg Group, the world’s leading food and drug consulting firm. If you have any questions or thoughts on this blog post or others, please contact us.