Remember the Zicam debacle? To catch you up, Zicam has been promoted for years as a “homeopathic cold remedy”. It is of course neither. Since it contains measurable amounts of zinc, it isn’t “homeopathic”, and since there is no cure for the common cold, it’s not a remedy. In addition to having neither of it’s promoted qualities, the FDA has received hundreds of reports of people losing their sense of smell (became “anosmic”) after using intranasal Zicam. As Steve Novella has pointed out, there is some scientific evidence pointing to a causal connection between zinc and anosmia. Now evidence is pointing toward possible mechanisms.
Adverse drug events are reported all the time. Nailing down whether they are significant can be difficult. First, there must be a plausible connection between the drug ingestion and the adverse event. Then cases have to be studied statistically to see if there is a true causal relationship. This is more difficult for Zicam since it has historically been more or less unregulated, being part of the homeopathic pharmacopoeia and not subject to the same regulation as other drugs (despite not being truly homeopathic). Despite this, the number of reports about Zicam was concerning enough for the FDA to issue a warning.
BiochemBelle tipped me off to a fascinating new study in PLoS One. This new study did a lot of things right in trying to illuminate this issue. For one thing, they used Zicam itself rather than a generic zinc preparation. They then tested Zicam in a mouse model and found loss of smell. Then the took human nasal tissue and exposed it to Zicam and found significant cell death. In both models, they also exposed the subjects (either mice or human olfactory neurons) to other substances commonly used with Zicam, such as nasal corticosteroids, vasoconstrictors, and saline. Not only did Zicam cause damage that other common cold medications did not, the damage was severe enough to be permanent.
This is a damning report. Given the lack of benefit of zinc preparations and the risk of serious neurologic damage, they should be taken off the market. It also points to the wider problem of medicines being classified as “homeopathic”, despite having measurable amounts of an active ingredient. The homeopathic pharmacopoeia is a bad joke—it contains unregulated fake medicines, and unregulated, untested, and potentially unsafe real medicines. This loophole for quackery needs to be closed before people suffer worse fates than loss of one of their primary senses.
References
Lim, J., Davis, G., Wang, Z., Li, V., Wu, Y., Rue, T., & Storm, D. (2009). Zicam-Induced Damage to Mouse and Human Nasal Tissue PLoS ONE, 4 (10) DOI: 10.1371/journal.pone.0007647