New studies have investigated the use of theophylline intranasal for treating loss of sense of smell after recovery from COVID-19. Theophylline is typically used to treat asthma, COPD, and other respiratory conditions. Its use in treating loss of smell has been studied for many years now but only recently came into popular attention. This was due to the prevalence of smell disturbances that were found to linger after recovering from COVID-19 infection. While the research is not conclusive, the results are promising that theophylline may be an effective treatment for loss of smell.
History of Theophylline
Theophylline is a naturally occurring chemical found in tea, chocolate, and other plants. As a drug it is used to treat COPD, asthma, and other respiratory conditions. It works by relaxing bronchial smooth muscle. Theophylline was actually first extracted from tea leaves in the late 1800s and synthesized a few years later, but it took a few more decades to be discovered as a therapy for asthma. Later a syrup form was developed and then an oral tablet. A compounding pharmacy is able to make a nasal form as well, which is the form currently being studied for treating loss of smell.
Research on Theophylline for Loss of Smell
Anosmia is a partial or full loss of smell. Anosmia often occurs during and after a viral infection and is especially common with COVID-19. The chronic inflammation of the nasal passages that occurs during an upper respiratory infection often causes some loss of smell. With COVID-19, the loss of smell is thought to have a different mechanism of action, however. Many patients who recover from the virus have lingering symptoms of loss of smell and/or taste.
The studies that have been conducted on loss of smell in COVID-19 patients have shown some benefit. In initial studies there was little difference between the treatment and placebo groups, so a dose-escalation study was conducted. In this study, 100mg nasal irrigation of theophylline was given twice daily for 7 days. If the patients tolerated this dosage, it was increased to 200mg for the next 7 days. Dosages were increased to a maximum of 800mg daily.
Since the normal starting dose for oral theophylline is 300mg, the researchers expected the higher intranasal doses to be well tolerated. When taken orally, the full dosage exerts systemic effects. With intranasal use, the actual systemic effect is much lower. For example, the 800mg intranasal dose corresponds to an approximately 20mg oral dose as it applies to systemic effects.
After 4 weeks of theophylline treatment in this dose escalation study, 4 of 10 participants reported somewhat improved smell, and 6 said their olfaction remained the same. Since there were only 11 participants total in this study, it is not sufficient to draw conclusions about theophylline’s effectiveness. However it did open up the possibility of researching higher dosages that may be more effective.
How is Theophylline Used?
Theophylline can be compounded in the form of a nasal spray for use in treating anosmia. A compounding pharmacy can make this formulation with a prescription from your doctor. A nasal spray uses a typical nasal spray bottle while a nasal irrigation is a higher volume treatment that uses a sinus rinse bottle. Theophylline intranasal is frequently prescribed for daily use until symptoms of anosmia are no longer present.
Articles
Mixed results for nasal theophylline to treat COVID-related loss of smell – CIDRAP
Theophylline nasal irrigation studied in COVID-19-related smell loss – Medical Xpress
Smell Changes and Efficacy of Nasal Theophylline (SCENT) irrigation – Washington University School of Medicine