Insulin fast-dissolving film for intranasal delivery via olfactory region, a promising approach for the treatment of anosmia in COVID-19 patients: Design, in-vitro characterization and clinical evaluation

A Comprehensive Review of COVID-19-Related Olfactory Deficiency: Unraveling Associations with Neurocognitive Disorders and Magnetic Resonance Imaging Findings

Olfactory dysfunction (OD) is one of the most common symptoms in COVID-19 patients and can impact patients' lives significantly. The aim of this review was to investigate the multifaceted impact of COVID-19 on the olfactory system and to provide an overview of magnetic resonance (MRI) findings and neurocognitive disorders in patients with COVID-19-related OD. Extensive searches were conducted across PubMed, Scopus, and Google Scholar until 5 December 2023. The included articles were 12 observational studies and 1 case report that assess structural changes in olfactory structures, highlighted through MRI, and 10 studies correlating the loss of smell with neurocognitive disorders or mood disorders in COVID-19 patients. MRI findings consistently indicate volumetric abnormalities, altered signal intensity of olfactory bulbs (OBs), and anomalies in the olfactory cortex among COVID-19 patients with persistent OD. The correlation between OD and neurocognitive deficits reveals associations with cognitive impairment, memory deficits, and persistent depressive symptoms. Treatment approaches, including olfactory training and pharmacological interventions, are discussed, emphasizing the need for sustained therapeutic interventions. This review points out several limitations in the current literature while exploring the intricate effects of COVID-19 on OD and its connection to cognitive deficits and mood disorders. The lack of objective olfactory measurements in some studies and potential validity issues in self-reports emphasize the need for cautious interpretation. Our research highlights the critical need for extensive studies with larger samples, proper controls, and objective measurements to deepen our understanding of COVID-19's long-term effects on neurological and olfactory dysfunctions.

Intranasal insulin for COVID-19-related smell loss

BACKGROUND

Quantitative (hyposmia and anosmia) and qualitative (phantosmia and parosmia) olfactory disorders are common consequences of COVID-19 infection found in more than 38% of patients even months after resolution of acute disease. SARS-CoV-2 has tropism for angiotensin-converting enzyme 2 (ACE2) in the respiratory system, suggesting that it is the mechanism of damage to the olfactory neuroepithelium and of involvement at the central nervous system. The olfactory bulb is the organ with the highest insulin uptake in the central nervous system. Insulin increases the production of Growth Factors (GF); therefore, in this study, the administration of intranasal insulin is proposed as a viable treatment for olfactory disturbances. The aim of this study was to obtain improvement in olfaction after 4 weeks of intranasal insulin administration in a group of patients presenting chronic olfactory disturbances secondary to COVID-19 infection, quantified using the Threshold, Discrimination, and Identification (TDI) score based on the Sniffin Sticks®.

METHODS

Experimental, longitudinal, prolective and prospective study of patients with a previous diagnosis of COVID-19 in the last 3-18 months and who persisted with anosmia or hyposmia. The sample size was calculated with "satulator". The intervention was performed from January to May 2022. Throughout four appointments, a baseline olfactory measurement was obtained using the TDI score based on the Sniffin Sticks® test. In the first three appointments, Gelfoam® cottonoids soaked in 40 IU of NPH insulin were placed on the nasal roof of each nostril for 15 min. Descriptive statistics, student's paired t test and a multiple linear regression were utilized to ascertain statistical significance of the outcome on the TDI score obtained on the fourth and final appointment.

RESULTS

27 patients were included in the study. Table 1 summarizes the sample characteristics. The results exhibit that 93% of the sample had an improvement. The initial mean TDI score was 67% (63-71) compared to the final mean of 83% (80-86, p < 0.01). TDI subsection analysis is shown in Table 2. There was no significant difference in pre-intervention and post-intervention glucose measurements after the intranasal insulin administration.

CONCLUSIONS

The administration of intranasal insulin has promising results, pointing towards an alternative of treatment for chronic olfactory disturbances secondary to neuroepithelial damage caused by upper respiratory tract infections. Furthermore, this is the first study to use a three-point assessment of olfaction in post-COVID-19 patients, while using the Sniffin Sticks® TDI score adapted to Latin Spanish.

Mechanism and treatment of olfactory dysfunction caused by coronavirus disease 2019

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Since the start of the pandemic, olfactory dysfunction (OD) has been reported as a common symptom of COVID-19. In some asymptomatic carriers, OD is often the first and even the only symptom. At the same time, persistent OD is also a long-term sequela seen after COVID-19 that can have a serious impact on the quality of life of patients. However, the pathogenesis of post-COVID-19 OD is still unclear, and there is no specific treatment for its patients. The aim of this paper was to review the research on OD caused by SARS-CoV-2 infection and to summarize the mechanism of action, the pathogenesis, and current treatments.

The Potential of Films as Transmucosal Drug Delivery Systems

Pharmaceutical films are polymeric formulations used as a delivery platform for administration of small and macromolecular drugs for local or systemic action. They can be produced by using synthetic, semi-synthetic, or natural polymers through solvent casting, electrospinning, hot-melt extrusion, and 3D printing methods, and depending on the components and the manufacturing methods used, the films allow the modulation of drug release. Moreover, they have advantages that have drawn interest in the development and evaluation of film application on the buccal, nasal, vaginal, and ocular mucosa. This review aims to provide an overview of and critically discuss the use of films as transmucosal drug delivery systems. For this, aspects such as the composition of these formulations, the theories of mucoadhesion, and the methods of production were deeply considered, and an analysis of the main transmucosal pathways for which there are examples of developed films was conducted. All of this allowed us to point out the most relevant characteristics and opportunities that deserve to be taken into account in the use of films as transmucosal drug delivery systems.

Outcome and Safety of Insulin in the Management of Smell Loss: A Systematic Review

Background: Olfactory dysfunction can negatively impact the quality of life and increase the risk of danger from warning odors. Various factors can cause olfactory dysfunction, including COVID-19 infection, which has increased anosmia cases. No medications are approved; however, recent studies have suggested that intranasal insulin could effectively treat olfactory dysfunction. Aim: To comprehensively evaluate the effectiveness and safety of intranasal insulin in treating olfactory dysfunction. Materials and Methods: PubMed, Google Scholar, and CENTRAL databases were searched using specific keywords, and the outputs were screened using the Rayyan AI system. Original research articles published without time frame limitations that reported the relevant outcomes were included. The reviewers performed the screening and data extraction, and any disagreements were resolved by a third senior author. Results: This systematic review identified 66 references from 3 databases, with 45 articles meeting the criteria for review after duplicates were removed. Six articles met the inclusion criteria and were selected, including 177 subjects. The selected studies consisted of various study designs, including pilot studies, placebo-controlled trials, crossover studies, and randomized clinical trials. The findings showed that intranasal insulin therapy had beneficial effects on olfactory function. Specifically, improvements were observed in olfactory detection and discrimination in patients with post-COVID-19 anosmia, olfactory threshold performance in healthy participants, and odor identification in hyposmic patients. However, there were variations in the observed effects based on different doses of insulin administered and gender differences. It also shows that using insulin provides good outcomes. Using it intranasally was safe and did not cause any complications. Conclusion: Intranasal insulin has shown promising results as a potentially safe treatment for olfactory dysfunction. Studies suggest that it can improve olfactory thresholds. Further studies are needed to investigate optimal doses and potential gender differences in response.

Intranasal Insulin for the Treatment of Persistent Post-COVID-19 Olfactory Dysfunction

OBJECTIVE

To investigate if intranasal insulin could be a treatment option for those suffering from recalcitrant olfactory dysfunction due to COVID-19.

STUDY DESIGN

Prospective interventional cohort with a single group.

SETTING

Sixteen volunteers with anosmia, severe hyposmia, or moderate hyposmia for more than 60 days as sequelae of severe acute respiratory syndrome coronavirus 2 infections were selected for the study. All volunteers reported that standard therapies, such as corticosteroids, have failed to improve their olfactory function.

METHODS

Olfactory function was assessed by the Chemosensory Clinical Research Center test of olfaction (COT) before and after the intervention. Changes in qualitative, quantitative, and global COT scores were investigated. The insulin therapy session consisted of placing into each olfactory cleft 2 pieces of gelatin sponge soaked with neutral protamine Hagedorn (NPH) insulin, 40 IU on each side. The procedure was repeated twice a week for 1 month. Glycaemic blood level was measured before and after each session.

RESULTS

The qualitative COT score rose 1.53 points, p = .0001, 95% confidence interval (CI) (-2.12 to -0.94). The quantitative COT score increased by 2.00 points, p = .0002, 95% CI (-3.59 to -1.41). Global COT score had an improvement of 2.01 points, p = .00003, 95% CI (-2.7 to -1.3). Glycaemic blood level dropped on average 10.4 mg/dL, p < .00003, 95% CI (8.1-12.8).

CONCLUSION

Our results suggest that the administration of NPH insulin into the olfactory cleft yields a rapid improvement in the sense of smell of patients suffering from persistent post-COVID-19 olfactory dysfunction. Moreover, the procedure seems to be safe and tolerable.

Post-COVID-19 Anosmia and Therapies: Stay Tuned for New Drugs to Sniff Out

Background: Anosmia is defined as the complete absence of olfactory function, which can be caused by a variety of causes, with upper respiratory tract infections being among the most frequent causes. Anosmia due to SARS-CoV-2 infection has attracted attention given its main role in symptomatology and the social impact of the pandemic. Methods: We conducted systematic research in a clinicaltrials.gov database to evaluate all active clinical trials worldwide regarding drug therapies in adult patients for anosmia following SARS-CoV-2 infection with the intention of identifying the nearby prospects to treat Anosmia. We use the following search terms: "Anosmia" AND "COVID-19" OR "SARS-CoV-2" OR "2019 novel coronavirus". Results: We found 18 active clinical trials that met our criteria: one phase 1, one phase 1-2, five phases 2, two phases 2-3, three phases 3, and six phases 4 studies were identified. The drug therapies that appear more effective and promising are PEA-LUT and Cerebrolysin. The other interesting drugs are 13-cis-retinoic acid plus aerosolized Vitamin D, dexamethasone, and corticosteroid nasal irrigation. Conclusions: COVID-19 has allowed us to highlight how much anosmia is an important and debilitating symptom for patients and, above all, to direct research to find a therapy aimed at curing the symptom, whether it derives from SARS-CoV-2 infection or other infections of the upper airways. Some of these therapies are very promising and are almost at the end of experimentation. They also provide hope in this field, which not addressed until recently.

Cholecalciferol-load films for the treatment of nasal burns caused by cauterization of the hypertrophied inferior turbinate: formulation, in vivo study, and clinical assessment

Nasal turbinate hypertrophy is among the most common nasal obstruction disorders, affecting the patient's quality of life significantly. Endoscopic submucosal diathermy is a prevalent cauterization procedure for treating turbinate hypertrophy. Regrettably, the nasal burn associated with diathermy typically heals slowly causing facial pain and nasal bleeding and possibly resulting in synechiae formation. In the current study, we have developed, for the first time, a polymeric film loaded with cholecalciferol for local treatment of nasal burns. The casting method was used to prepare films of different compositions of polymers such as chitosan, polyvinyl alcohol (PVA), Carbopol 971p (CP971p), and hydroxypropyl methylcellulose (HPMC) as well as a plasticizer. Several characterizations were performed for the cholecalciferol-loaded films (e.g. weight, thickness, content uniformity, surface pH, folding endurance, disintegration time, and in vitro release) to select the optimal formulation. The optimal formulation (F4) displayed compatibility between the used polymers and the drug. In vivo animal study was carried out to assess the healing efficacy of the formulated cholecalciferol-loaded film. The rabbits treated with the cholecalciferol-loaded film demonstrated significantly higher mRNA expression of the growth factor TGF-β and significantly lower mRNA expression of the proinflammatory cytokine TNF-α and IL-1β compared to the plain film treated group and the untreated control group. A randomized, single-blinded, parallel, controlled clinical trial was conducted on 20 patients scheduled to undergo endoscopic submucous diathermy. The results of the clinical study demonstrated significant reductions in facial pain and nasal bleeding scores for the nostrils treated with cholecalciferol-loaded films in comparison to the nostrils treated with plain films. Furthermore, the endoscopic examination showed good healing for 95% of the cholecalciferol-loaded film-treated nostrils. In conclusion, the optimized film can be considered an opportune approach for enhancing the healing rate of nasal burns and thus reducing the downsides of the diathermy procedure.

Pathogenesis Underlying Neurological Manifestations of Long COVID Syndrome and Potential Therapeutics

The development of long-term symptoms of coronavirus disease 2019 (COVID-19) more than four weeks after primary infection, termed "long COVID" or post-acute sequela of COVID-19 (PASC), can implicate persistent neurological complications in up to one third of patients and present as fatigue, "brain fog", headaches, cognitive impairment, dysautonomia, neuropsychiatric symptoms, anosmia, hypogeusia, and peripheral neuropathy. Pathogenic mechanisms of these symptoms of long COVID remain largely unclear; however, several hypotheses implicate both nervous system and systemic pathogenic mechanisms such as SARS-CoV2 viral persistence and neuroinvasion, abnormal immunological response, autoimmunity, coagulopathies, and endotheliopathy. Outside of the CNS, SARS-CoV-2 can invade the support and stem cells of the olfactory epithelium leading to persistent alterations to olfactory function. SARS-CoV-2 infection may induce abnormalities in innate and adaptive immunity including monocyte expansion, T-cell exhaustion, and prolonged cytokine release, which may cause neuroinflammatory responses and microglia activation, white matter abnormalities, and microvascular changes. Additionally, microvascular clot formation can occlude capillaries and endotheliopathy, due to SARS-CoV-2 protease activity and complement activation, can contribute to hypoxic neuronal injury and blood-brain barrier dysfunction, respectively. Current therapeutics target pathological mechanisms by employing antivirals, decreasing inflammation, and promoting olfactory epithelium regeneration. Thus, from laboratory evidence and clinical trials in the literature, we sought to synthesize the pathophysiological pathways underlying neurological symptoms of long COVID and potential therapeutics.

Therapeutic options of post-COVID-19 related olfactory dysfunction: a systematic review and meta-analysis

BACKGROUND

Olfactory dysfunction is a typical post-COVID-19 presentation, affecting patients' quality of life. There are currently multiple treatment options in this group of patients such as oral and intranasal corticosteroids, olfactory training, oral vitamin-mineral supplementation, amongst others. This meta-analysis aims to consolidate existing evidence for current therapies in patients with persistent olfactory dysfunction related to COVID-19 infection and evaluate the possible role of corticosteroid add-on therapy in olfactory training.

METHODOLOGY

A systematic review and meta-analysis to study current treatments/interventions for olfactory dysfunction in post-COVID-19 infection were conducted. Data were pooled for the meta-analysis. The outcomes include subjective or objective olfactory assessment major and minor adverse reactions.

RESULTS

Eleven studies (1414 participants) were included in this review, with six studies (916 participants) then assessed for the meta-analysis. Combined treatment of intranasal corticosteroid (INCS) with olfactory training (OT) has no benefit over OT monotherapy from both a VAS score improvement and identification component of Sniffin' Sticks test standpoint. In addition, there were no differences in improvement of TDI score between combined oral corticosteroid (OCS) with OT therapy compared to OT alone. Olfactory function was, however, significantly improved after OT.

CONCLUSION

There were no significant differences in the improvement of olfactory scores in combination INCS+OT or OCS+OT therapies compared to OT monotherapy. However, there is improvement in olfactory function after OT.

[COVID-19-associated anosmia]

The article is a systematic review of the literature data summarizes to date on the issue of COVID-19-associated anosmia. We mainly used full-text and abstract electronic databases (PubMed, Scopus and Web of Science). The paper discusses hypothetical mechanisms of development, clinical features, as well as methods of diagnosis and treatment of COVID-19-associated anosmia.

Development of In Vitro Evaluation System for Assessing Drug Dissolution Considering Physiological Environment in Nasal Cavity

Estimating the dissolution behavior of a solid in the nasal mucus is challenging for solid dosage forms designed for the nasal application as the solid dissolves into nasal mucus and permeates through the mucosa. In the current study, the dissolution behavior of powders in the artificial nasal fluid was investigated using a 3D-printed chamber system to establish in vitro evaluation system for the dissolution of solid formulations that can simulate the intranasal environment in vivo. The dissolution rates of the five model drugs correlated with their solubility (r2 = 0.956, p < 0.01). The permeation rate of drugs across the Calu-3 cell layers after powder application depends on the membrane permeability of the drug. An analysis of membrane permeability considering the dissolution of powders showed the possibility of characterizing whether the drug in the powder was dissolution-limited or permeation-limited. This suggests that critical information can be obtained to understand which mechanism is more effective for the improvement of drug absorption from powders. This study indicates that the elucidation of drug dissolution behavior into nasal mucus is an important factor for the formulation of nasal powders and that the in vitro system developed could be a useful tool.

The Potential of Corchorus olitorius Seeds Buccal Films for Treatment of Recurrent Minor Aphthous Ulcerations in Human Volunteers

Aphthous ulcers are very common disorders among different age groups and are very noxious and painful. The incidence of aphthous ulcer recurrence is very high and it may even last for a maximum of 6 days and usually, patients cannot stand its pain. This study aims to prepare a buccoadhesive fast dissolving film containing Corchorus olitorius seed extract to treat recurrent minor aphthous ulceration (RMAU) in addition to clinical experiments on human volunteers. An excision wound model was used to assess the in vivo wound healing potential of Corchorus olitorius L. seed extract, with a focus on wound healing molecular targets such as TGF-, TNF-, and IL-1. In addition, metabolomic profiling using HR-LCMS for the crude extract of Corchorus olitorius seeds was explored. Moreover, molecular docking experiments were performed to elucidate the binding confirmation of the isolated compounds with three molecular targets (TNF-α, IL-1β, and GSK3). Additionally, the in vitro antioxidant potential of C. olitorius seed extract using both H2O2 and superoxide radical scavenging activity was examined. Clinical experiments on human volunteers revealed the efficiency of the prepared C. olitorius seeds buccal fast dissolving film (CoBFDF) in relieving pain and wound healing of RMAU. Moreover, the wound healing results revealed that C. olitorius seed extract enhanced wound closure rates (p ≤ 0.001), elevated TGF-β levels and significantly downregulated TNF-α and IL-1β in comparison to the Mebo-treated group. The phenotypical results were supported by biochemical and histopathological findings, while metabolomic profiling using HR-LCMS for the crude extract of Corchorus olitorius seeds yielded a total of 21 compounds belonging to diverse chemical classes. Finally, this study highlights the potential of C. olitorius seed extract in wound repair uncovering the most probable mechanisms of action using in silico analysis.

Management of Anosmia in COVID-19: A Comprehensive Review

With the evolving understanding of COVID-19, a thorough analysis of the effects of this unique coronavirus on the affected people's olfactory abilities could highlight the disease's specific course of treatment. Researchers have discovered that the neurological side effects of SARS-CoV-2 infection include acute anosmia and ageusia. This work aims to review the relevant mechanisms, provide information on COVID-19-related anosmia, and suggest a novel approach to treating long-term anosmia brought on by coronavirus disease. For that, we did a thorough literature assessment of the subject from various online resources, including PubMed, Scopus, and Google Scholar. We evaluated the publications that described anosmia in COVID-19 and its management. In patients with SARS-CoV-2 infections, the angiotensin-converting enzyme two receptor plays a crucial role in the anosmia process. Olfactory systems are directly harmed by new coronaviruses when they connect with sustentacular cells' ACE-2 (Angiotensin converting enzyme-2) receptors. Other suggested processes include the virus's infiltration of the olfactory nerve and the ensuing local inflammation. Therefore, neuroprotective, anti-inflammatory, or depolarizing medications may be helpful for COVID-19 individuals who have lost their sense of smell. According to the available data, we found out olfactory training, topical or oral corticosteroids, caffeine, insulin, or minocycline may effectively treat COVID-19 odor loss. A novel method of treating long-term COVID-19 with persistent anosmia can be suggested based on recent investigations. The path to effective anosmia management is still somewhat hazy, but there is hope that we can find the right treatment plan with the right clinical trials and additional research. People who lost their sense of smell during COVID-19 can be reassured that recovery is typically possible.

Interventions for the treatment of persistent post-COVID-19 olfactory dysfunction

BACKGROUND

Olfactory dysfunction is a common consequence of COVID-19 infection and persistent symptoms can have a profound impact on quality of life. At present there is little guidance on how best to treat this condition. A variety of interventions have been suggested to promote recovery, including medication and olfactory training. However, it is uncertain whether any intervention is of benefit. This is an update of the 2021 review with one additional study added.  OBJECTIVES: 1) To evaluate the benefits and harms of any intervention versus no treatment for people with persisting olfactory dysfunction due to COVID-19 infection.  2) To keep the evidence up-to-date, using a living systematic review approach.  SEARCH METHODS: The Cochrane ENT Information Specialist searched the Cochrane ENT Register; Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE; Ovid Embase; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished trials. The date of the latest search was 20 October 2021.   SELECTION CRITERIA: We included randomised controlled trials (RCTs) in people with COVID-19 related olfactory disturbance that had persisted for at least four weeks. We included any intervention compared to no treatment or placebo.  DATA COLLECTION AND ANALYSIS: We used standard Cochrane methods. Our primary outcomes were the recovery of sense of smell, disease-related quality of life and serious adverse effects. Secondary outcomes were the change in sense of smell, general quality of life, prevalence of parosmia and other adverse effects (including nosebleeds/bloody discharge). We used GRADE to assess the certainty of the evidence for each outcome.

MAIN RESULTS

We included two studies with 30 participants. The studies evaluated the following interventions: systemic corticosteroids plus intranasal corticosteroid/mucolytic/decongestant and palmitoylethanolamide plus luteolin.  Systemic corticosteroids plus intranasal corticosteroid/mucolytic/decongestant compared to no intervention We included a single RCT with 18 participants who had anosmia for at least 30 days following COVID-19 infection. Participants received a 15-day course of oral corticosteroids combined with nasal irrigation (consisting of an intranasal corticosteroid/mucolytic/decongestant solution) or no intervention. Psychophysical testing was used to assess olfactory function at 40 days. This is a single, small study and for all outcomes the certainty of evidence was very low. We are unable to draw meaningful conclusions from the numerical results. Palmitoylethanolamide plus luteolin compared to no intervention We included a single RCT with 12 participants who had anosmia or hyposmia for at least 90 days following COVID-19 infection. Participants received a 30-day course of palmitoylethanolamide and luteolin or no intervention. Psychophysical testing was used to assess olfactory function at 30 days. This is a single, small study and for all outcomes the certainty of evidence was very low. We are unable to draw meaningful conclusions from the numerical results.

AUTHORS' CONCLUSIONS

There is very limited evidence available on the efficacy and harms of treatments for persistent olfactory dysfunction following COVID-19 infection. However, we have identified a number of ongoing trials in this area. As this is a living systematic review we will update the data regularly, as new results become available.

Interventions for the prevention of persistent post-COVID-19 olfactory dysfunction

BACKGROUND

Loss of olfactory function is well recognised as a symptom of COVID-19 infection, and the pandemic has resulted in a large number of individuals with abnormalities in their sense of smell. For many, the condition is temporary and resolves within two to four weeks. However, in a significant minority the symptoms persist. At present, it is not known whether early intervention with any form of treatment (such as medication or olfactory training) can promote recovery and prevent persisting olfactory disturbance. This is an update of the 2021 review with four studies added.

OBJECTIVES

1) To evaluate the benefits and harms of any intervention versus no treatment for people with acute olfactory dysfunction due to COVID-19 infection.  2) To keep the evidence up-to-date, using a living systematic review approach.  SEARCH METHODS: The Cochrane ENT Information Specialist searched the Cochrane ENT Register; Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE; Ovid Embase; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished trials. The date of the latest search was 20 October 2021.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) in people with COVID-19 related olfactory disturbance, which had been present for less than four weeks. We included any intervention compared to no treatment or placebo.  DATA COLLECTION AND ANALYSIS: We used standard Cochrane methods. Our primary outcomes were the presence of normal olfactory function, serious adverse effects and change in sense of smell. Secondary outcomes were the prevalence of parosmia, change in sense of taste, disease-related quality of life and other adverse effects (including nosebleeds/bloody discharge). We used GRADE to assess the certainty of the evidence for each outcome.  MAIN RESULTS: We included five studies with 691 participants. The studies evaluated the following interventions: intranasal corticosteroid sprays, intranasal corticosteroid drops, intranasal hypertonic saline and zinc sulphate.  Intranasal corticosteroid spray compared to no intervention/placebo We included three studies with 288 participants who had olfactory dysfunction for less than four weeks following COVID-19. Presence of normal olfactory function The evidence is very uncertain about the effect of intranasal corticosteroid spray on both self-rated recovery of olfactory function and recovery of olfactory function using psychophysical tests at up to four weeks follow-up (self-rated: risk ratio (RR) 1.19, 95% confidence interval (CI) 0.85 to 1.68; 1 study; 100 participants; psychophysical testing: RR 2.3, 95% CI 1.16 to 4.63; 1 study; 77 participants; very low-certainty evidence).  Change in sense of smell The evidence is also very uncertain about the effect of intranasal corticosteroid spray on self-rated change in the sense of smell (at less than 4 weeks: mean difference (MD) 0.5 points lower, 95% CI 1.38 lower to 0.38 higher; 1 study; 77 participants; at > 4 weeks to 3 months: MD 2.4 points higher, 95% CI 1.32 higher to 3.48 higher; 1 study; 100 participants; very low-certainty evidence, rated on a scale of 1 to 10, higher scores mean better olfactory function). Intranasal corticosteroids may make little or no difference to the change in sense of smell when assessed with psychophysical testing (MD 0.2 points, 95% CI 2.06 points lower to 2.06 points higher; 1 study; 77 participants; low-certainty evidence, 0- to 24-point scale, higher scores mean better olfactory function).  Serious adverse effects The authors of one study reported no adverse effects, but their intention to collect these data was not pre-specified so we are uncertain if these were systematically sought and identified. The remaining two studies did not report on adverse effects.  Intranasal corticosteroid drops compared to no intervention/placebo We included one study with 248 participants who had olfactory dysfunction for ≤ 15 days following COVID-19. Presence of normal olfactory function Intranasal corticosteroid drops may make little or no difference to self-rated recovery at > 4 weeks to 3 months (RR 1.00, 95% CI 0.89 to 1.11; 1 study; 248 participants; low-certainty evidence). No other outcomes were assessed by this study.  Data on the use of hypertonic saline nasal irrigation and the use of zinc sulphate to prevent persistent olfactory dysfunction are included in the full text of the review.

AUTHORS' CONCLUSIONS

There is very limited evidence available on the efficacy and harms of treatments for preventing persistent olfactory dysfunction following COVID-19 infection. However, we have identified a number of ongoing trials in this area. As this is a living systematic review we will update the data regularly, as new results become available.

Formulation and In Vitro Characterization of a Vacuum-Dried Drug–Polymer Thin Film for Intranasal Application

Intranasal drug applications show significant therapeutic potential for diverse pharmaceutical modalities. Because the formulation applied to the nasal cavity is discharged to the pharyngeal side by mucociliary clearance, the formulation should be dissolved effectively in a limited amount of mucus within its retention time in the nasal cavity. In this study, to develop novel formulations with improved dissolution behavior and compatibility with the intranasal environment, a thin-film formulation including drug and polymer was prepared using a vacuum-drying method. The poorly water-soluble drugs ketoprofen, flurbiprofen, ibuprofen, and loxoprofen were dissolved in a solvent comprising water and methanol, and evaporated to obtain a thin film. Physical analyses using differential scanning calorimetry (DSC), powder X-ray diffraction analysis (PXRD), and scanning electron microscopy SEM revealed that the formulations were amorphized in the film. The dissolution behavior of the drugs was investigated using an in vitro evaluation system that mimicked the intranasal physiological environment. The amorphization of drugs formulated with polymers into thin films using the vacuum-drying method improved the dissolution rate in artificial nasal fluid. Therefore, the thin film developed in this study can be safely and effectively used for intranasal drug application.

Riech- und Schmeckstörungen

Ziel der vorliegenden Übersicht ist es, einen Überblick über die Ätiologie und Diagnostik von Riech- und Schmeckstörungen zu geben. Da etwa 5 % der Allgemeinbevölkerung betroffen sind, ist es ein häufiges Krankheitsbild. Riechen und Schmecken erhielten v. a. zuletzt Aufmerksamkeit während des Aufkommens der SARS-CoV-2-Pandemie, wobei eine plötzlich aufgetretene Riech- und/oder Schmeckstörung zu den typischen Symptomen zählt. Daneben sind Riechstörungen in der Frühdiagnostik neurodegenerativer Erkrankungen von Bedeutung. Häufig zeigen Patienten mit Riechstörungen Zeichen einer Depression. Die Auswirkungen von Riech‑/Schmeckstörungen sind also umfangreich, die Therapiemöglichkeiten aktuell begrenzt. Nach einem Einblick in die Ätiologie werden Diagnostik und Therapiemöglichkeiten auf dem aktuellen Stand der Literatur erörtert. Auch zukunftsweisende Behandlungsvorstellungen, wie z. B. autologe Schleimhauttransplantationen oder olfaktorische Implantate, werden angesprochen.

Untangling Mucosal Drug Delivery: Engineering, Designing, and Testing Nanoparticles to Overcome the Mucus Barrier

Mucus is a complex viscoelastic gel and acts as a barrier covering much of the soft tissue in the human body. High vascularization and accessibility have motivated drug delivery to various mucosal surfaces; however, these benefits are hindered by the mucus layer. To overcome the mucus barrier, many nanomedicines have been developed, with the goal of improving the efficacy and bioavailability of drug payloads. Two major nanoparticle-based strategies have emerged to facilitate mucosal drug delivery, namely, mucoadhesion and mucopenetration. Generally, mucoadhesive nanoparticles promote interactions with mucus for immobilization and sustained drug release, whereas mucopenetrating nanoparticles diffuse through the mucus and enhance drug uptake. The choice of strategy depends on many factors pertaining to the structural and compositional characteristics of the target mucus and mucosa. While there have been promising results in preclinical studies, mucus-nanoparticle interactions remain poorly understood, thus limiting effective clinical translation. This article reviews nanomedicines designed with mucoadhesive or mucopenetrating properties for mucosal delivery, explores the influence of site-dependent physiological variation among mucosal surfaces on efficacy, transport, and bioavailability, and discusses the techniques and models used to investigate mucus-nanoparticle interactions. The effects of non-homeostatic perturbations on protein corona formation, mucus composition, and nanoparticle performance are discussed in the context of mucosal delivery. The complexity of the mucosal barrier necessitates consideration of the interplay between nanoparticle design, tissue-specific differences in mucus structure and composition, and homeostatic or disease-related changes to the mucus barrier to develop effective nanomedicines for mucosal delivery.

ESCMID rapid guidelines for assessment and management of long COVID

Scope

The aim of these guidelines is to provide evidence-based recommendations for the assessment and management of individuals with persistent symptoms after acute COVID-19 infection and to provide a definition for this entity, termed ‘long COVID’.

Methods

We performed a search of the literature on studies addressing epidemiology, symptoms, assessment, and treatment of long COVID. The recommendations were grouped by these headings and by organ systems for assessment and treatment. An expert opinion definition of long COVID is provided. Symptoms were reviewed by a search of the available literature. For assessment recommendations, we aimed to perform a diagnostic meta-analysis, but no studies provided relevant results. For treatment recommendations we performed a systematic review of the literature in accordance with the PRISMA statement. We aimed to evaluate patient-related outcomes, including quality of life, return to baseline physical activity, and return to work. Quality assessment of studies included in the systematic review is provided according to study design.

Recommendations

Evidence was insufficient to provide any recommendation other than conditional guidance. The panel recommends considering routine blood tests, chest imaging, and pulmonary functions tests for patients with persistent respiratory symptoms at 3 months. Other tests should be performed mainly to exclude other conditions according to symptoms. For management, no evidence-based recommendations could be provided. Physical and respiratory rehabilitation should be considered. On the basis of limited evidence, the panel suggests designing high-quality prospective clinical studies/trials, including a control group, to further evaluate the assessment and management of individuals with persistent symptoms of COVID-19.

[Olfactory and gustatory disorders]

Ziel der vorliegenden Übersicht ist es, einen Überblick über die Ätiologie und Diagnostik von Riech- und Schmeckstörungen zu geben. Da etwa 5 % der Allgemeinbevölkerung betroffen sind, ist es ein häufiges Krankheitsbild. Riechen und Schmecken erhielten v. a. zuletzt Aufmerksamkeit während des Aufkommens der SARS-CoV-2-Pandemie, wobei eine plötzlich aufgetretene Riech- und/oder Schmeckstörung zu den typischen Symptomen zählt. Daneben sind Riechstörungen in der Frühdiagnostik neurodegenerativer Erkrankungen von Bedeutung. Häufig zeigen Patienten mit Riechstörungen Zeichen einer Depression. Die Auswirkungen von Riech‑/Schmeckstörungen sind also umfangreich, die Therapiemöglichkeiten aktuell begrenzt. Nach einem Einblick in die Ätiologie werden Diagnostik und Therapiemöglichkeiten auf dem aktuellen Stand der Literatur erörtert. Auch zukunftsweisende Behandlungsvorstellungen, wie z. B. autologe Schleimhauttransplantationen oder olfaktorische Implantate, werden angesprochen.

Using the Intranasal Route to Administer Drugs to Treat Neurological and Psychiatric Illnesses: Rationale, Successes, and Future Needs

While the intranasal administration of drugs to the brain has been gaining both research attention and regulatory success over the past several years, key fundamental and translational challenges remain to fully leveraging the promise of this drug delivery pathway for improving the treatment of various neurological and psychiatric illnesses. In response, this review highlights the current state of understanding of the nose-to-brain drug delivery pathway and how both biological and clinical barriers to drug transport using the pathway can been addressed, as illustrated by demonstrations of how currently approved intranasal sprays leverage these pathways to enable the design of successful therapies. Moving forward, aiming to better exploit the understanding of this fundamental pathway, we also outline the development of nanoparticle systems that show improvement in delivering approved drugs to the brain and how engineered nanoparticle formulations could aid in breakthroughs in terms of delivering emerging drugs and therapeutics while avoiding systemic adverse effects.

Potential pharmacologic treatments for COVID-19 smell and taste loss: A comprehensive review

The acute loss of taste and smell following COVID-19 are hallmark symptoms that affect 20-85% of patients. However, the pathophysiology and potential treatments of COVID-19 smell and taste loss are not fully understood. We searched the literature to review the potential pathologic pathways and treatment options for COVID-19 smell and taste loss. The interaction of novel coronavirus with ACE-2 receptors expressed on sustentacular cells and taste buds results in direct damage to the olfactory and gustatory systems. Also, the invasion of the virus to the olfactory neurons and consequent local inflammation are other proposed mechanisms. Therefore, COVID-19 patients with smell or taste loss may benefit from neuroprotective, anti-inflammatory, or depolarizing agents. Based on the current evidence, phosphodiesterase inhibitors, insulin, and corticosteroids can be promising for the management of COVID-19 smell and taste loss. This review provided crucial information for treating COVID-19-related smell and/or taste loss, urging to perform large clinical trials to find optimum treatment options.

Mechanism of Anosmia Caused by Symptoms of COVID-19 and Emerging Treatments

The occurrence of anosmia, the loss or change in sense of smell, is one of the most common symptoms of COVID-19 experienced by almost 53% of those affected. Several hypotheses explain the mechanism of anosmia in patients suffering from COVID-19. This study aims to review the related mechanisms and answer the questions regarding COVID-19-related anosmia as well as propose a new strategy for treatment of long-term anosmia as a result of COVID-19 infection. This paper covers all of the studies investigating olfactory disorders following COVID-19 infection and explains the possible reasons for the correlated anosmia, including olfactory cleft syndrome, local inflammation in the nasal epithelium, early apoptosis of olfactory cells, changes in olfactory cilia and odor transmission, damage to microglial cells, effect on olfactory bulbs, epithelial olfactory injury, and impairment of olfactory neurons and stem cells. The key questions that arise in this field have been discussed, such as why prevalent anosmia is varied among the age categories and among sexes and the correlation of anosmia with mild or severe COVID-19 infection. The angiotensin-converting enzyme 2 receptor is a significant player in the mechanism of anosmia in COVID-19 patients. Based on current studies, a novel approach to treat long-COVID-19 with ongoing anosmia has been proposed. The fields of smart drug delivery, tissue engineering, and cell therapy provide a hypothesized strategy that can minimize the side effects of current treatments and support efficient recovery of the olfactory system.

Interventions for the prevention of persistent post-COVID-19 olfactory dysfunction

BACKGROUND

Loss of olfactory function is well recognised as a cardinal symptom of COVID-19 infection, and the ongoing pandemic has resulted in a large number of affected individuals with abnormalities in their sense of smell. For many, the condition is temporary and resolves within two to four weeks. However, in a significant minority the symptoms persist. At present, it is not known whether early intervention with any form of treatment (such as medication or olfactory training) can promote recovery and prevent persisting olfactory disturbance.  OBJECTIVES: To assess the effects (benefits and harms) of interventions that have been used, or proposed, to prevent persisting olfactory dysfunction due to COVID-19 infection. A secondary objective is to keep the evidence up-to-date, using a living systematic review approach.  SEARCH METHODS: The Cochrane ENT Information Specialist searched the Cochrane COVID-19 Study Register; Cochrane ENT Register; CENTRAL; Ovid MEDLINE; Ovid Embase; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished studies. The date of the search was 16 December 2020.

SELECTION CRITERIA

Randomised controlled trials including participants who had symptoms of olfactory disturbance following COVID-19 infection. Individuals who had symptoms for less than four weeks were included in this review. Studies compared any intervention with no treatment or placebo.  DATA COLLECTION AND ANALYSIS: We used standard Cochrane methodological procedures. Our primary outcomes were the presence of normal olfactory function, serious adverse effects and change in sense of smell. Secondary outcomes were the prevalence of parosmia, change in sense of taste, disease-related quality of life and other adverse effects (including nosebleeds/bloody discharge). We used GRADE to assess the certainty of the evidence for each outcome.  MAIN RESULTS: We included one study of 100 participants, which compared an intranasal steroid spray to no intervention. Participants in both groups were also advised to undertake olfactory training for the duration of the trial. Data were identified for only two of the prespecified outcomes for this review, and no data were available for the primary outcome of serious adverse effects. Intranasal corticosteroids compared to no intervention (all using olfactory training) Presence of normal olfactory function after three weeks of treatment was self-assessed by the participants, using a visual analogue scale (range 0 to 10, higher scores = better). A score of 10 represented "completely normal smell sensation". The evidence is very uncertain about the effect of intranasal corticosteroids on self-rated recovery of sense of smell (estimated absolute effect 619 per 1000 compared to 520 per 1000, risk ratio (RR) 1.19, 95% confidence interval (CI) 0.85 to 1.68; 1 study; 100 participants; very low-certainty evidence).  Change in sense of smell was not reported, but the self-rated score for sense of smell was reported at the endpoint of the study with the same visual analogue scale (after three weeks of treatment). The median scores at endpoint were 10 (interquartile range (IQR) 9 to 10) for the group receiving intranasal corticosteroids, and 10 (IQR 5 to 10) for the group receiving no intervention (1 study; 100 participants; very low-certainty evidence).

AUTHORS' CONCLUSIONS

There is very limited evidence regarding the efficacy of different interventions at preventing persistent olfactory dysfunction following COVID-19 infection. However, we have identified a small number of additional ongoing studies in this area. As this is a living systematic review, the evidence will be updated regularly to incorporate new data from these, and other relevant studies, as they become available.  For this (first) version of the living review, we identified a single study of intranasal corticosteroids to include in this review, which provided data for only two of our prespecified outcomes. The evidence was of very low certainty, therefore we were unable to determine whether intranasal corticosteroids may have a beneficial or harmful effect.

Interventions for the treatment of persistent post-COVID-19 olfactory dysfunction

BACKGROUND

Olfactory dysfunction is an early and sensitive marker of COVID-19 infection. Although self-limiting in the majority of cases, when hyposmia or anosmia persists it can have a profound effect on quality of life. Little guidance exists on the treatment of post-COVID-19 olfactory dysfunction, however several strategies have been proposed from the evidence relating to the treatment of post-viral anosmia (such as medication or olfactory training).

OBJECTIVES

To assess the effects (benefits and harms) of interventions that have been used, or proposed, to treat persisting olfactory dysfunction due to COVID-19 infection. A secondary objective is to keep the evidence up-to-date, using a living systematic review approach.  SEARCH METHODS: The Cochrane ENT Information Specialist searched the Cochrane COVID-19 Study Register; Cochrane ENT Register; CENTRAL; Ovid MEDLINE; Ovid Embase; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished studies. The date of the search was 16 December 2020.

SELECTION CRITERIA

Randomised controlled trials including participants who had symptoms of olfactory disturbance following COVID-19 infection. Only individuals who had symptoms for at least four weeks were included in this review. Studies compared any intervention with no treatment or placebo.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures. Primary outcomes were the recovery of sense of smell, disease-related quality of life and serious adverse effects. Secondary outcomes were the change in sense of smell, general quality of life, prevalence of parosmia and other adverse effects (including nosebleeds/bloody discharge). We used GRADE to assess the certainty of the evidence for each outcome.

MAIN RESULTS

We included one study with 18 participants, which compared the use of a 15-day course of oral steroids combined with nasal irrigation (consisting of an intranasal steroid/mucolytic/decongestant solution) with no intervention. Psychophysical testing was used to assess olfactory function at baseline, 20 and 40 days. Systemic corticosteroids plus intranasal steroid/mucolytic/decongestant compared to no intervention Recovery of sense of smell was assessed after 40 days (25 days after cessation of treatment) using the Connecticut Chemosensory Clinical Research Center (CCCRC) score. This tool has a range of 0 to 100, and a score of ≥ 90 represents normal olfactory function. The evidence is very uncertain about the effect of this intervention on recovery of the sense of smell at one to three months (5/9 participants in the intervention group scored ≥ 90 compared to 0/9 in the control group; risk ratio (RR) 11.00, 95% confidence interval (CI) 0.70 to 173.66; 1 study; 18 participants; very low-certainty evidence). Change in sense of smell was assessed using the CCCRC score at 40 days. This study reported an improvement in sense of smell in the intervention group from baseline (median improvement in CCCRC score 60, interquartile range (IQR) 40) compared to the control group (median improvement in CCCRC score 30, IQR 25) (1 study; 18 participants; very low-certainty evidence). Serious adverse events andother adverse events were not identified in any participants of this study; however, it is unclear how these outcomes were assessed and recorded (1 study; 18 participants; very low-certainty evidence).

AUTHORS' CONCLUSIONS

There is very limited evidence available on the efficacy and harms of treatments for persistent olfactory dysfunction following COVID-19 infection. However, we have identified other ongoing trials in this area. As this is a living systematic review we will update the data regularly, as new results become available. For this (first) version of the living review we identified only one study with a small sample size, which assessed systemic steroids and nasal irrigation (intranasal steroid/mucolytic/decongestant). However, the evidence regarding the benefits and harms from this intervention to treat persistent post-COVID-19 olfactory dysfunction is very uncertain.