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Objectives/hypothesis: In this study we investigated the effectiveness of vitamin A in postinfectious and posttraumatic smell disorders. A possible effect of vitamin A is likely due to the stimulation of regeneration and repair of the peripheral olfactory system., Study Design: Double-blind, randomized, placebo-controlled clinical trial., Methods: A total of 52 patients (age range, 20-70 years; mean age, 52 years) participated, 26 of whom received placebo (7 male, 19 female) and another 26 verum (8 male, 18 female). A standardized history was obtained in each patient. Olfactory function was measured by means of the Sniffin' Sticks test kit, a validated technique to investigate odor thresholds, odor discrimination, and odor identification. Vitamin A was prescribed at a dose of 10,000 IU per day for 3 months. Follow-up testing was performed on average 5 months after the first investigation., Results: Forty-four percent of all patients reported recovery of their sense of smell; 29% of the participants exhibited significant improvement in measured olfactory function. However, there was no significant difference between the outcome of patients receiving verum or placebo., Conclusions: The systemic application of vitamin A at a dose of 10,000 IU per day for 3 months does not appear to be useful in the treatment of postinfectious or posttraumatic olfactory loss., (Copyright © 2012 The American Laryngological, Rhinological, and Otological Society, Inc.)

The "Sniffin' Sticks" test kit is a validated and commonly used tool for assessment of olfactory function in subjects with normal sense of smell and in individuals with smell loss. That test incorporates subtests for odor threshold, discrimination, and identification. To gain higher subtest reproducibility, tests on odor discrimination and odor identification were extended using 32 instead of the usually applied 16 single trials each. In developing the extended Sniffin' Sticks test, a number of preliminary experiments were performed in 46 healthy, normosmic individuals 1) to evaluate intensity and familiarity of the additionally selected odors, 2) to select distractors for the discrimination and identification test, and 3) to evaluate the test-retest reliability of each subtest. Furthermore, the extended test was applied to 126 patients with olfactory loss and 71 normosmic individuals. Follow-up investigation could be performed in 69 controls within an average interval of 4 days. Results revealed significant differences between patients and healthy subjects. Estimated intensity and familiarity of the newly selected 16 items of the discrimination test did not differ significantly from the 16 standard items. Test-retest reliability was found to be r = 0.80 (odor discrimination), r = 0.88 (odor identification), and r = 0.92 (odor threshold). In conclusion, the extended test kit allows a precise evaluation of olfactory function, especially when different olfactory tasks are assessed using individual subtests. Furthermore, the high test-retest reliability of both the 16 and the 32-item tests allows the evaluation of even relatively small changes of olfactory function over time by means of either test.

Objectives/Hypothesis: Infection of the upper respiratory tract is one of the most common causes of olfactory loss. One of the possible underlying pathologic pathways is an increase of apoptosis of olfactory receptor neurons. Therefore, treatment with the antibiotic minocycline, which has been shown to act as an antiapoptotic agent, is thought to accelerate improvement of olfactory function. To investigate this idea, 55 patients with postinfectious olfactory dysfunction were tested for their olfactory ability. Study Design: Randomized, prospective, double-blind, placebo-controlled. Methods: Olfactory function was examined by means of a standardized psychophysical method (Sniffin’ Sticks) before and 7 months after a 3-week treatment with either minocycline (2 < 50 mg/d) or a placebo. Results: Statistical analyses did not reveal any influence of the treatment on the progress of olfactory function, possibly indicating that pathologic changes other than apoptosis contribute to postinfectious olfactory loss, either on a peripheral level (e.g., scarring/reorganization of the olfactory epithelium) or on a central nervous level. Conclusions: In conclusion, the present results indicate that minocycline in the given dosage has little or no effect on the recovery of human olfactory function following postinfectious olfactory loss. However, spontaneous recovery is found in approximately 20% of the patients over an observation period of 7 months. [ABSTRACT FROM AUTHOR]