Intranasal Theophylline for Loss of Smell/Taste
Theophylline is a nonselective phosphodiesterase enzyme inhibitor indicated for use in patients with acute exacerbations of asthma and reversible airflow obstruction associated with asthma. Studies have found that loss of smell and/or taste was correlated with growth factors cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Theophylline increases the levels of cAMP and cGMP, resulting in improved tast and smell. Adverse effects (restlessness, anxiety, headache, diarrhea, abdominal pain) can be seen with oral and intravenous formulations/administration but are not seen with intranasal administration.
Use in COVID-19
The SCENT2 trial is currently being conducted by the Washington University College of Medicine looking into the efficacy of utilizing intranasal theophylline in patients who are experiencing a lack of smell and/or taste that has persisted for over 3 months after getting over a suspected Covid infection. Depending on these findings, the intranasal formulation of theophylline may become more mainstream instead of a special compound made by specialty pharmacies.
Theophylline Package Insert. Hospira, Inc; 2008.
Henkin RI, Schultz M, Minnick-Pope L. Intranasal theophylline treatment of hyposmia and hypogeusia: a pilot study. Jama Otolaryngol Head Neck Surg. 2012:138(11):1064-1070. Doi:10.1001/2013.jamaoto342
Smell in Covid-19 and efficacy of nasal theophylline (SCENT2) ClinicalTrials.gov identifier: NCTO4789499. Updated July 7, 2021. Accessed December 28, 2021.