Effective Treatment of Smell Loss with Theophylline

Abstract

While patients with smell loss in the US number in the millions there has been no effective method to either evaluate or treat the majority of them. These patients exhibit several causes for their loss including post viral infection, head injury and allergic rhinitis. Their semll loss has been measured objectively by psychophysical techniques and subjectively by quantitative evaluation of loss. We described the major biochemical defect causing these sensory losses‐decreased cAMP and cGMP in nasal mucus; this defect inhibits growth and development of olfactory receptor cells. To improve patients’ sensory loss we attempted to correct their observed biochemical defect by increasing cAMP and cGMP though use of the phosphodiesterase inhibitor theophylline which we gave orally to 309 patients at doses of 200–600 mg for 2–8 months. Psychophysical measurements of smell function improved in over 70%. Subjective responses improved in only 144 (47%); among these responders were 27% who improved 51% and 20% who improved 84%. 165 (53%) did not improve‐nonresponders‐ who improved 0.5%. Responders had significantly less severe smell loss than did nonresponders but there were no differences in age or blood levels of theophylline. These results indicate that patients with smell loss of several etiologies with this biochemical defect can be treated effectively with theophylline to improve smell fucntion.