Intranasal sodium citrate solution improves olfaction in post-viral hyposmia

Background: Calcium plays an integral role in olfactory signal transduction, including feedback inhibition. Sodium citrate acts as a calcium sequestrant and when applied intranasally, reduces free calcium available for feedback inhibition, which should theoretically improve olfaction. We aimed to investigate the utility of intranasal sodium citrate in improving the olfactory function of hyposmic patients, by performing this prospective placebo controlled, single-blinded trial. Methodology: Monorhinal olfactory testing for odour identification and threshold was performed in hyposmic patients using “Sniffin’ Sticks”, before and after treatment. Treatment consisted of sodium citrate solution application to the olfactory cleft. Sodium chloride solution was applied to the contralateral olfactory cleft, which therefore acted as placebo control. Patients were blinded to the side of sodium citrate application, and side of treatment was randomized between patients. Results: 57 patients participated in the trial, aged 22-79. Causes of hyposmia included: post-viral (7); posttraumatic (10); sinonasal (30) and idiopathic (10). Compared with placebo, there was significant improvement in the identification scores of participants with post-viral hyposmia, following sodium citrate treatment. No significant change in olfactory function occurred for either identification or threshold in any other aetiological subgroup. Conclusions: Intranasal sodium citrate may be of benefit to patients with post-viral hyposmia.