These cyclic nucleotides are growth factors for olfactory (related to smell) and other neural tissues.
"I had earlier done the first total protein analysis of saliva and mucous to learn what was in there, and found these growth factors and found that people who couldn't smell had diminished levels of the factors," Henkin explained. "Theophylline, in a sense, inhibits the breakdown of growth factors so more are going to stick around."
Henkin and his team have now confirmed the efficacy of theophylline in this context in 312 patients with hyposmia over a seven-year study period.
All of the study participants had decreased levels of growth factors cAMP and/or cGMP, as measured in their nasal mucous.
More than half of participants said their sense of smell improved after being treated with theophylline, while more than 20 percent said their smell returned to normal. Larger doses of the compound and longer treatment times resulted in greater improvements.
"People who had relatively mild or moderate disease seemed to respond to this treatment but those patients tend to respond to other treatments as well," Kuppersmith said. "Most of those who had severe or complete loss of sense of smell didn't respond, which is typical of a lot of treatments out there."
Also, he said, "some people who lose their sense of smell get better anyway, especially if they have mild cases, so they would have gotten better with or without treatment."
But, Kuppersmith added, for certain patients this might be a helpful option if other things don't work.
Side effects of theophylline were minimal, the researchers noted, but can
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