Mohamad 2021.

Methods	Parallel‐group randomised controlled trial
Participants	Adult participants with loss of sense of smell after COVID‐19 infection Inclusion criteria Aged 18 to 70 years Anosmia after COVID‐19 infection (no further details provided) Exclusion criteria Nasal polyps Fracture of the nose < 6 months before enrolment to the trial Nasal surgery < 6 months before enrolment to the trial Planned sample size: estimated enrolment 40 participants
Interventions	Intervention: insulin fast‐dissolving film containing 100 IU of insulin applied intranasally 3 times a week for 4 weeks Comparator: formulated bio‐adhesive fast‐dissolving film containing no drugs applied intranasally 3 times a week for 4 weeks
Outcomes	Outcomes of interest in the review: Primary outcomes: Presence of normal olfactory function Not reported Serious adverse effects  Not reported Change in sense of smell Improvement in sense of smell as measured with the butanol threshold test. This test establishes smell threshold through identification of an odour (butyl alcohol) versus water. The detection threshold is recorded as the concentration at which the patient correctly identifies the butanol on 5 consecutive trials. The scoring relates the patient's threshold to a normal subject population. Measured at 4 weeks Secondary outcomes: Prevalence of parosmia Not reported Change in sense of taste Not reported Disease‐related quality of life Not reported Other adverse effects (including nosebleeds/bloody discharge) Not reported Other outcomes reported by the study: No additional outcomes are reported
Notes	Trial registered in Egypt. It is unclear from the description of this trial whether participants had symptoms of olfactory disturbance for fewer than 4 weeks from the onset of COVID‐19. The duration of anosmia is reported in the publication, with a range of 2 to 10, but it is not clear whether this is days or weeks. We have attempted to contact the authors for clarification, but are awaiting a response.