Smell in Covid-19 and Efficacy of Nasal Theophylline

Inclusion Criteria: * Olfactory dysfunction that has persisted for \>3 months following suspected COVID-19 infection * Residing within the states of Missouri or Illinois. * Can read, write, and understand English. Exclusion Criteria: * History of olfactory dysfunction prior to COVID-19 infection * Use of concomitant therapies specifically for the treatment of olfactory dysfunction * History of olfactory dysfunction longer than 12 months * Known existence of nasal polyps, prior sinonasal, or anterior skull-based surgery * Dependence on theophylline for comorbid conditions such as asthma and COPD * History of an allergic reaction to theophylline or other methylxanthines * History of neurodegenerative disease (ie. Alzheimer's dementia, Parkinson's disease, Lewy body dementia, frontotemporal dementia) * Pregnant or breastfeeding mothers * Current use of medications with significant interactions with theophylline, which include cimetidine, ciprofloxacin, disulfiram, enoxacin, fluvoxamine, interferon-alpha, lithium, mexiletine, phenytoin, propafenone, propranolol, tacrine, thiabendazole, ticlopidine, and troleandomycin. * Pre-existing arrhythmias or seizures