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The Taste and Smell Clinic
  


April 2004

Zicam and Smell Loss 


Zicam is an over the counter drug used as a nasal spray to relieve symptoms associated with colds and influenza. The spray is inserted directly into the nostrils as directed by the drug label. People have usually used this spray after the initial onset of cold symptoms but some people apparently have used this spray as a cold preventative. This spray has proven very popular and is available in many drug stores.

We have received reports from many people who stated that after spraying Zicam into their nostrils they noted an extensive and severe burning sensation in the region where they had sprayed the drug and after a short period of time (hours-days) they noted a loss of smell. Most of the people who have communicated with us tell us that their smell loss is total and that they have experienced little or no return in their smell function. This has been disconcerting and surprising since there was no warning given about this side effect on the drug label and none of these patients had ever before experienced such a loss of sensory function.

I was asked to comment on these effects by the Dow Jones News Service in February 2004 and a report about these comments was published by this service.

Dr. Bruce Jafek, a distinguished otolaryngologist in Denver, CO reported about this effect in 2003 at a clinical meeting in the US after evaluating patients who experienced these symptoms.

At The Taste and Smell Clinic, Washington, DC I have evaluated several patients who have claimed to have lost their smell function after use of this drug. Careful measurements of their smell acuity indicates loss of smell function consistent with their clinical complaints. Some of these patients also experienced distortion of smell consistent with the deafferentation hypersensitivity associated with loss of any significant sensory input (e.g., phantom limb syndrome).

We have treated several of these patients after extensive evaluation of the cause of their complaints. Treatment has restored some function in these patients but it is too early to be definitive about the efficacy of the various therapeutic modes used to alleviate these patientsí symptoms.

The mechanism responsible for these alterations in smell function is quite clear. Zicam is a zinc containing drug. While zinc is critical for maintenance of normal smell function through its action as a cofactor in carbonic anhydrase VI, given directly into the nostrils at high concentrations, it can initiate direct toxic destruction of the olfactory epithelium with which it comes into contact in its spray form. The associated nasal burning is another manifestation of this local toxicity. In animal studies performed in the past, direct insertion of zinc into the nostrils initiated total loss of smell function as measured by sophisticated computer driven, objective techniques. Examination of the olfactory epithelium in these animals after zinc application showed destruction of this tissue.

In animals, some regeneration of the olfactory epithelium occurs over time with some return of smell function. However, mice and rats are quite different from humans. The question of return of smell function after Zicam use in humans is unanswered.

In order to balance this putative drug effect with clinical history it is useful to understand that “colds” per se can initiate smell loss and subsequent smell distortion in humans. These sensory changes are due to viral induced changes in growth factor function which initiates apoptotic destruction of the olfactory epithelium. Distinguishing direct effects of Zicam from that of a “cold associated virus” can be difficult. However, where the detrimental effect of Zicam can be clearly determined is in cases in which people have used this drug on a preventative basis at which time they had no cold symptoms but drug use initiated nasal burning and subsequent smell loss and distortion.

These comments illustrate several important concepts.

  1. Loss and distortion of smell function can occur with use of Zicam as well as with many other drugs (see 1).

  2. Loss and distortion of smell function are symptoms of clinical importance just as are symptoms of headache, muscle pain, indigestion or diarrhea - they deserve medical attention.

  3. Loss and distortion of smell function are symptoms which require careful evaluation to insure that the cause of these sensory changes can be defined - many diseases have these symptoms associated with their onset (e.g, hypothyroidism, Alzheimer disease, various forms of cancer, etc.).

  4. Loss and distortion of smell function can be treated effectively if the antecedent cause can be identified.

  1. Henkin, R.I. Drug induced taste and smell disorders: incidence, mechanisms and management related primarily to treatment of sensory receptor dysfunction. Drug Safety. 11: 310-377, 1994.

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