Ototoxicity: A Challenge in Diagnosis and Treatment

The Current State of Proteomics and Metabolomics for Inner Ear Health and Disease

Characterising inner ear disorders represents a significant challenge due to a lack of reliable experimental procedures and identified biomarkers. It is also difficult to access the complex microenvironments of the inner ear and investigate specific pathological indicators through conventional techniques. Omics technologies have the potential to play a vital role in revolutionising the diagnosis of ear disorders by providing a comprehensive understanding of biological systems at various molecular levels. These approaches reveal valuable information about biomolecular signatures within the cochlear tissue or fluids such as the perilymphatic and endolymphatic fluid. Proteomics identifies changes in protein abundance, while metabolomics explores metabolic products and pathways, aiding the characterisation and early diagnosis of diseases. Although there are different methods for identifying and quantifying biomolecules, mass spectrometry, as part of proteomics and metabolomics analysis, could be utilised as an effective instrument for understanding different inner ear disorders. This study aims to review the literature on the application of proteomic and metabolomic approaches by specifically focusing on Meniere's disease, ototoxicity, noise-induced hearing loss, and vestibular schwannoma. Determining potential protein and metabolite biomarkers may be helpful for the diagnosis and treatment of inner ear problems.

Ototoxicity: a high risk to auditory function that needs to be monitored in drug development

Hearing loss constitutes a major global health concern impacting approximately 1.5 billion people worldwide. Its incidence is undergoing a substantial surge with some projecting that by 2050, a quarter of the global population will experience varying degrees of hearing deficiency. Environmental factors such as aging, exposure to loud noise, and the intake of ototoxic medications are implicated in the onset of acquired hearing loss. Ototoxicity resulting in inner ear damage is a leading cause of acquired hearing loss worldwide. This could be minimized or avoided by early testing of hearing functions in the preclinical phase of drug development. While the assessment of ototoxicity is well defined for drug candidates in the hearing field - required for drugs that are administered by the otic route and expected to reach the middle or inner ear during clinical use - ototoxicity testing is not required for all other therapeutic areas. Unfortunately, this has resulted in more than 200 ototoxic marketed medications. The aim of this publication is to raise awareness of drug-induced ototoxicity and to formulate some recommendations based on available guidelines and own experience. Ototoxicity testing programs should be adapted to the type of therapy, its indication (targeting the ear or part of other medications classes being potentially ototoxic), and the number of assets to test. For multiple molecules and/or multiple doses, screening options are available: in vitro (otic cell assays), ex vivo (cochlear explant), and in vivo (in zebrafish). In assessing the ototoxicity of a candidate drug, it is good practice to compare its ototoxicity to that of a well-known control drug of a similar class. Screening assays provide a streamlined and rapid method to know whether a drug is generally safe for inner ear structures. Mammalian animal models provide a more detailed characterization of drug ototoxicity, with a possibility to localize and quantify the damage using functional, behavioral, and morphological read-outs. Complementary histological measures are routinely conducted notably to quantify hair cells loss with cochleogram. Ototoxicity studies can be performed in rodents (mice, rats), guinea pigs and large species. However, in undertaking, or at the very least attempting, all preclinical investigations within the same species, is crucial. This encompasses starting with pharmacokinetics and pharmacology efficacy studies and extending through to toxicity studies. In life read-outs include Auditory Brainstem Response (ABR) and Distortion Product OtoAcoustic Emissions (DPOAE) measurements that assess the activity and integrity of sensory cells and the auditory nerve, reflecting sensorineural hearing loss. Accurate, reproducible, and high throughput ABR measures are fundamental to the quality and success of these preclinical trials. As in humans, in vivo otoscopic evaluations are routinely carried out to observe the tympanic membrane and auditory canal. This is often done to detect signs of inflammation. The cochlea is a tonotopic structure. Hair cell responsiveness is position and frequency dependent, with hair cells located close to the cochlea apex transducing low frequencies and those at the base transducing high frequencies. The cochleogram aims to quantify hair cells all along the cochlea and consequently determine hair cell loss related to specific frequencies. This measure is then correlated with the ABR & DPOAE results. Ototoxicity assessments evaluate the impact of drug candidates on the auditory and vestibular systems, de-risk hearing loss and balance disorders, define a safe dose, and optimize therapeutic benefits. These types of studies can be initiated during early development of a therapeutic solution, with ABR and otoscopic evaluations. Depending on the mechanism of action of the compound, studies can include DPOAE and cochleogram. Later in the development, a GLP (Good Laboratory Practice) ototoxicity study may be required based on otic related route of administration, target, or known potential otic toxicity.

Awareness and Attitude About Ototoxic Drugs Among Medical Doctors in Arar City, Saudi Arabia

OBJECTIVES

The purpose of this study was to assess the awareness of ototoxicity among medical doctors in Arar City, Saudi Arabia.

METHODS

This is a cross-sectional study based on a pre-formed validated questionnaire (Appendix) that included three sections covering participants' demographic data (three questions), their attitudes (five questions), and knowledge (13 questions) regarding drug-induced ototoxicity.

RESULTS

After obtaining their informed consent, 213 physicians from government and private sector health facilities in Arar were enrolled in the study. Interns and general practitioners represented 57.8% of the participants; consultants represented 17.8%. Only 71.8% of participants were interested in drug-induced ototoxicity, while 26.3% considered ototoxicity a rare complication. Approximately 90% of the participants were knowledgeable about the adverse effects of drugs on the vestibulocochlear system, and 26.7% reported having experienced cases of drug-induced ototoxicity in their practice. Participants showed an overall knowledge score about ototoxicity of 9.3±3.27 (out of 14). The knowledge score was significantly higher (p-value=0.0007) for participants with more years of clinical experience. The most widely known ototoxic drug for participants was frusemide (72.3%), followed by aminoglycoside (68.5%), while acetaminophen (44.1%) ototoxicity was the least known among participants.

CONCLUSION

Awareness of drug-induced ototoxicity is satisfactory among physicians in the Northern Borders region. However, workshops about all types of drugs with ototoxic effects and the main lines for the management of drug-induced ototoxicity are recommended to increase awareness.

Modern In Vitro Techniques for Modeling Hearing Loss

Sensorineural hearing loss (SNHL) is a prevalent and growing global health concern, especially within operational medicine, with limited therapeutic options available. This review article explores the emerging field of in vitro otic organoids as a promising platform for modeling hearing loss and developing novel therapeutic strategies. SNHL primarily results from the irreversible loss or dysfunction of cochlear mechanosensory hair cells (HCs) and spiral ganglion neurons (SGNs), emphasizing the need for innovative solutions. Current interventions offer symptomatic relief but do not address the root causes. Otic organoids, three-dimensional multicellular constructs that mimic the inner ear's architecture, have shown immense potential in several critical areas. They enable the testing of gene therapies, drug discovery for sensory cell regeneration, and the study of inner ear development and pathology. Unlike traditional animal models, otic organoids closely replicate human inner ear pathophysiology, making them invaluable for translational research. This review discusses methodological advances in otic organoid generation, emphasizing the use of human pluripotent stem cells (hPSCs) to replicate inner ear development. Cellular and molecular characterization efforts have identified key markers and pathways essential for otic organoid development, shedding light on their potential in modeling inner ear disorders. Technological innovations, such as 3D bioprinting and microfluidics, have further enhanced the fidelity of these models. Despite challenges and limitations, including the need for standardized protocols and ethical considerations, otic organoids offer a transformative approach to understanding and treating auditory dysfunctions. As this field matures, it holds the potential to revolutionize the treatment landscape for hearing and balance disorders, moving us closer to personalized medicine for inner ear conditions.

Relationship Between Chloroquine or Hydroxychloroquine Use and Hearing Disorders: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

Chloroquine and its analog hydroxychloroquine are derivatives of 4-aminoquinoline and are regularly used in the treatment of malaria and autoimmune diseases. Among the side effects of these drugs, alterations associated with the auditory system are frequently mentioned. Thus, the aim of this systematic review is to systematically review publications on hearing disorders and chloroquine or hydroxychloroquine use.

MATERIALS AND METHODS

Inclusion criteria were observational or interventional studies on audiological assessment in participants who were using chloroquine or hydroxychloroquine. The methodological quality was independently assessed by two reviewers using the Meta-Analysis of Statistics: assessment and review Instrument. The certainty of the evidence was assessed using the GRADE tool.

RESULTS

A total of 1,372 non-duplicate papers were screened, out of which 17 were included in the final qualitative synthesis, and 5 studies in the meta-analysis. The odds ratio for the two subgroups evaluated did not show significance with no heterogeneity between the effects observed between the different diseases (I2=0%) and obtaining the global estimate of 0.76 (95% confidence interval [CI]=0.41-1.39; p>0.05). Despite the inclusion of papers with different disease samples, the heterogeneity observed in the analysis was low (I2= 0%) and prediction interval (95% PI=0.32-1.80; p>0.05) remained close to that estimated by the CI (95% CI=0.41-1.39; p>0.05). The certainty of the evidence assessed by the GRADE tool was considered very low due to the risk of bias, indirect evidence, and imprecision.

CONCLUSIONS

The findings of this study suggest that the use of chloroquine/hydroxychloroquine is not associated with hearing disorders.

The use of tele-audiology in ototoxicity monitoring: A scoping review

INTRODUCTION

Due to the growing burden of disease in South Africa, encompassing conditions such as tuberculosis, human immunodeficiency virus, and cancer, the holistic management of affected patients incorporating ototoxicity monitoring is a necessity. However, ototoxicity monitoring in developing countries may be limited due to a lack of resources and inadequate healthcare facilities. Subsequently, the use of tele-audiology may be a revolutionary technique with the potential to provide audiology services to under-served populations with limited access.

METHODS

The study aimed to describe the use of tele-audiology services in ototoxicity monitoring through a scoping review of English peer-reviewed articles from June 2009 to June 2020. Seventeen articles were purposively selected from the following databases: PubMed, Science Direct, Taylor and Francis Online, WorldCat, and Google Scholar. Data was extracted as per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses diagram and results were analyzed using deductive thematic analysis.

RESULTS AND DISCUSSION

While a minority of the studies indicated that the cost of implementation and network connectivity within a South African context pose as barriers, most researchers reported that tele-audiology provides a reliable, time-efficient, cost-effective, and easily accessible alternative for ototoxicity monitoring. Hardware including the WAHTS, KUDUwave, and OtoID, along with software such as the TabSINT, Otocalc, uHear, and the hearTest, have proven to be useful for ototoxicity monitoring. A need for further investigations regarding the feasibility of tele-audiology implementation in South Africa is evident. Despite this, it provides audiologists with an opportunity to offer contact-less services during COVID-19, thus, confirming its versatility as an augmentative method for ototoxicity monitoring.

Role of Kir4.1 Channels in Aminoglycoside-Induced Ototoxicity of Hair Cells

The Kir4.1 channel, an inwardly rectifying potassium ion (K+) channel, is located in the hair cells of the organ of Corti as well as the intermediate cells of the stria vascularis. The Kir4.1 channel has a crucial role in the generation of endolymphatic potential and maintenance of the resting membrane potential. However, the role and functions of the Kir4.1 channel in the progenitor remain undescribed. To observe the role of Kir4.1 in the progenitor treated with the one-shot ototoxic drugs (kanamycin and furosemide), we set the proper condition in culturing Immortomouse-derived HEI-OC1 cells to express the potassium-related channels well. And also, that was reproduced in mice experiments to show the important role of Kir4.1 in the survival of hair cells after treating the ototoxicity drugs. In our results, when kanamycin and furosemide drugs were cotreated with HEI-OC1 cells, the Kir4.1 channel did not change, but the expression levels of the NKCC1 cotransporter and KCNQ4 channel are decreased. This shows that inward and outward channels were blocked by the two drugs (kanamycin and furosemide). However, noteworthy here is that the expression level of Kir4.1 channel increased when kanamycin was treated alone. This shows that Kir4.1, an inwardly rectifying potassium channel, acts as an outward channel in place of the corresponding channel when the KCNQ4 channel, an outward channel, is blocked. These results suggest that the Kir4.1 channel has a role in maintaining K+ homeostasis in supporting cells, with K+ concentration compensator when the NKCC1 cotransporter and Kv7.4 (KCNQ4) channels are deficient.

Practice of Monitoring Cisplatin-Induced Ototoxicity by Audiology, ENT, and Oncology Specialists: A Survey-Based Study in a Single Italian Medical Center

Ototoxic drugs can result in hearing loss and tinnitus. Early detection of the ototoxic process can help minimize or prevent these consequences. The American Speech-Language-Hearing Association has provided guidelines for monitoring ototoxicity, whereas Italy has not yet implemented a national monitoring protocol. This study aims to assess the current state of ototoxicity monitoring in patients receiving cisplatin therapy. A self-administered survey has been used to gather information from oncologists, audiologists, and ENT specialists. The research was conducted at Santa Maria della Misericordia hospital in Perugia. Two questionnaires were administered, one to ENT/audiology specialists and another to oncology specialists. Both questionnaires were used to collect information on awareness of chemotherapy-induced ototoxicity. A comprehensive understanding of cisplatin-induced ototoxicity has been widely established (100%). The most commonly reported audiological symptoms by patients were hearing loss (100%) and tinnitus (87.5%). The majority of ENT and audiologists (93.8%) and oncologists (92.9%) expressed the need for a specific ototoxic monitoring program. However, they noted the absence of a well-defined ototoxicity monitoring protocol. A well-established and efficient ototoxic monitoring system facilitates early detection of ototoxic hearing loss and subsequent rehabilitation of inevitable hearing impairment.

Age-related hearing loss and its potential drug candidates: a systematic review

BACKGROUND

Age-related hearing loss (ARHL) is one of the main illnesses afflicting the aged population and has a significant negative impact on society, economy, and health. However, there is presently no appropriate therapeutic treatment of ARHL due to the absence of comprehensive trials.

OBJECTIVES

The goal of this review is to systematically evaluate and analyze recent statistics on the pathologic classifications, risk factors, treatment strategies, and drug candidates of ARHL, including that from traditional Chinese medicine (TCM), to provide potential new approaches for preventing and treating ARHL.

METHODS

Literature related to ARHL was conducted in databases such as PubMed, WOS, China National Knowledge Infrastructure (CNKI), and Wanfang from the establishment of the database to Jan, 2023. The pathology, causal factor, pathophysiological mechanism, treatment strategy, and the drug candidate of ARHL were extracted and pooled for synthesis.

RESULTS

Many hypotheses about the etiology of ARHL are based on genetic and environmental elements. Most of the current research on the pathology of ARHL focuses on oxidative damage, mitochondrial dysfunction, inflammation, cochlear blood flow, ion homeostasis, etc. In TCM, herbs belonging to the kidney, lung, and liver meridians exhibit good hearing protection. Seven herbs belonging to the kidney meridian, 9 belonging to the lung meridian, and 4 belonging to the liver meridian were ultimately retrieved in this review, such as Polygonum multiflorum Thunb., Panax ginseng C.A. Mey, and Pueraria lobata (Willd.) Ohwi. Their active compounds, 2,3,4',5-Tetrahydroxystilbene-2-O-D-glucoside, ginsenoside Rb1, and puerarin, may act as the molecular substance for their anti-ARHL efficacy, and show anti-oxidative, neuroprotective, anti-inflammatory, anti-apoptotic, or mitochondrial protective effects.

CONCLUSION

Anti-oxidants, modulators of mitochondrial function, anti-inflammation agents, vasodilators, K+ channel openers, Ca2+ channel blockers, JNK inhibitors, and nerve growth factors/neurotrophic factors all contribute to hearing protection, and herbs are an important source of potential anti-ARHL drugs.

Predicting Hearing Loss in Testicular Cancer Patients after Cisplatin-Based Chemotherapy

Testicular cancer is predominantly curable, but the long-term side effects of chemotherapy have a severe impact on life quality. In this research study, we focus on hearing loss as a part of overall chemotherapy-induced ototoxicity. This is a unique approach where we combine clinical data from the acclaimed nationwide Danish Testicular Cancer (DaTeCa)-Late database. Clinical and genetic data on 433 patients were collected from hospital files in October 2014. Hearing loss was classified according to the FACT/GOG-Ntx-11 version 4 self-reported Ntx6. Machine learning models combining a genome-wide association study within a nested cross-validated logistic regression were applied to identify patients at high risk of hearing loss. The model comprising clinical and genetic data identified 67% of the patients with hearing loss; however, this was with a false discovery rate of 49%. For the non-affected patients, the model identified 66% of the patients with a false omission rate of 19%. An area under the receiver operating characteristic (ROC-AUC) curve of 0.73 (95% CI, 0.71-0.74) was obtained, and the model suggests genes SOD2 and MGST3 as important in improving prediction over the clinical-only model with a ROC-AUC of 0.66 (95% CI, 0.65-0.66). Such prediction models may be used to allow earlier detection and prevention of hearing loss. We suggest a possible biological mechanism for cisplatin-induced hearing loss development. On confirmation in larger studies, such models can help balance treatment in clinical practice.

Potential Ototoxicity of Insulin-like Growth Factor 1 Receptor Signaling Inhibitors: An In Silico Drug Repurposing Study of the Regenerating Cochlear Neuron Transcriptome

Spiral ganglion neurons (SGNs) connect cochlear hair cells with higher auditory pathways and their degeneration due to drug toxicity (ototoxicity) contributes to hearing loss. This study aimed to identify drug classes that are negatively correlated with the transcriptome of regenerating SGNs. Human orthologs of differentially expressed genes within the regenerating neonatal mouse SGN transcriptome were entered into CMap and the LINCS unified environment and perturbation-driven gene expression was analyzed. The CMap connectivity scores ranged from 100 (positive correlation) to -100 (negative correlation). Insulin-like growth factor 1/receptor (IGF-1/R) inhibitors were highly negatively correlated with the regenerating SGN transcriptome (connectivity score: -98.87). A systematic literature review of clinical trials and observational studies reporting otologic adverse events (AEs) with IGF-1/R inhibitors identified 108 reports (6141 treated patients). Overall, 16.9% of the treated patients experienced any otologic AE; the rate was highest for teprotumumab (42.9%). In a meta-analysis of two randomized placebo-controlled trials of teprotumumab, there was a significantly higher risk of hearing-related (pooled Peto OR [95% CI]: 7.95 [1.57, 40.17]) and of any otologic AEs (3.56 [1.35, 9.43]) with teprotumumab vs. a placebo, whether or not dizziness/vertigo AEs were included. These results call for close audiological monitoring during IGF-1-targeted treatment, with prompt referral to an otolaryngologist should otologic AEs develop.

Role of mitochondrial dysfunction and oxidative stress in sensorineural hearing loss

Sensorineural hearing loss (SNHL) can either be genetically inherited or acquired as a result of aging, noise exposure, or ototoxic drugs. Although the precise pathophysiological mechanisms underlying SNHL remain unclear, an overwhelming body of evidence implicates mitochondrial dysfunction and oxidative stress playing a central etiological role. With its high metabolic demands, the cochlea, particularly the sensory hair cells, stria vascularis, and spiral ganglion neurons, is vulnerable to the damaging effects of mitochondrial reactive oxygen species (ROS). Mitochondrial dysfunction and consequent oxidative stress in cochlear cells can be caused by inherited mitochondrial DNA (mtDNA) mutations (hereditary hearing loss and aminoglycoside-induced ototoxicity), accumulation of acquired mtDNA mutations with age (age-related hearing loss), mitochondrial overdrive and calcium dysregulation (noise-induced hearing loss and cisplatin-induced ototoxicity), or accumulation of ototoxic drugs within hair cell mitochondria (drug-induced hearing loss). In this review, we provide an overview of our current knowledge on the role of mitochondrial dysfunction and oxidative stress in the development of SNHL caused by genetic mutations, aging, exposure to excessive noise, and ototoxic drugs. We also explore the advancements in antioxidant therapies for the different forms of acquired SNHL that are being evaluated in preclinical and clinical studies.

Sick Leave Due to Ear Diagnoses, a Nationwide Representative Registry of Mexico

Sickness absence from work is a measure of both poor health and social functioning. In order to assess the frequency of sick leave due to ear-related diagnoses, we performed a retrospective analysis on the registry of paid sick leave certificates supplied by the main social security institution in Mexico during the years 2018 and 2019, just prior to the SARS-CoV-2 pandemic. We observed that, in the two years, 22,053 sick leave certificates due to ear-related diagnoses were provided to 18,033 workers. The most frequent ear-related diagnoses were those of vestibular disorders (94.64%); among them, the most common diagnosis was Benign Paroxysmal Positional Vertigo (75.16%), followed by Labrynthitis and Meniere's disease (circa 8% each). A total of 4.63% of the diagnoses were related to external and middle ear disorders, and 0.71% were mainly related to hearing. Consistently, the highest cumulative days of sick leave required were given for the group of diagnoses related to vestibular disorders; although the less frequent diagnoses required the highest cumulative days per case (e.g., ototoxicity). During 2018 and 2019, the most frequent diagnoses of ear-related sick leave were due to vestibular diagnoses (particularly Benign Paroxysmal Positional Vertigo).

Association of Clinical Aspects and Genetic Variants with the Severity of Cisplatin-Induced Ototoxicity in Head and Neck Squamous Cell Carcinoma: A Prospective Cohort Study

Background: Cisplatin (CDDP) is a major ototoxic chemotherapy agent for head and neck squamous cell carcinoma (HNSCC) treatment. Clinicopathological features and genotypes encode different stages of CDDP metabolism, as their coexistence may influence the prevalence and severity of hearing loss. Methods: HNSCC patients under CDDP chemoradiation were prospectively provided with baseline and post-treatment audiometry. Clinicopathological features and genetic variants encoding glutathione S-transferases (GSTT1, GSTM1, GSTP1), nucleotide excision repair (XPC, XPD, XPF, ERCC1), mismatch repair (MLH1, MSH2, MSH3, EXO1), and apoptosis (P53, CASP8, CASP9, CASP3, FAS, FASL)-related proteins were analyzed regarding ototoxicity. Results: Eighty-nine patients were included, with a cumulative CDDP dose of 260 mg/m2. Moderate/severe ototoxicity occurred in 26 (29%) patients, particularly related to hearing loss at frequencies over 3000 Hertz. Race, body-mass index, and cumulative CDDP were independent risk factors. Patients with specific isolated and combined genotypes of GSTM1, GSTP1 c.313A>G, XPC c.2815A>C, XPD c.934G>A, EXO1 c.1762G>A, MSH3 c.3133A>G, FASL c.-844A>T, and P53 c.215G>C SNVs had up to 32.22 higher odds of presenting moderate/severe ototoxicity. Conclusions: Our data present, for the first time, the association of combined inherited nucleotide variants involved in CDDP efflux, DNA repair, and apoptosis with ototoxicity, which could be potential predictors in future clinical and genomic models.

Extended High-Frequency Audiometry for Ototoxicity Monitoring: A Longitudinal Evaluation of Drug-Resistant Tuberculosis Treatment

PURPOSE

The aim of this study was to describe extended high-frequency (EHF) pure-tone audiometry monitoring of ototoxicity in a longitudinal treatment program for drug-resistant tuberculosis (DRTB).

METHOD

This was a retrospective record review of longitudinal conventional (0.25-8 kHz) and EHF (9-16 kHz) audiometry for ototoxicity monitoring of DRTB patients undergoing treatment at community-based clinics between 2013 and 2017. Data from 69 patients with an average age of 37.9 years (SD = 11.2, range: 16.0-63.8 years) were included. Patients were assessed by primary health care audiologists (87%) or community health workers (13%) using portable audiological equipment. The average length of time between initial and exit assessments was 84.6 days (SD = 74.2, range: 2-335 days).

RESULTS

EHF ototoxicity of a mild or greater degree of hearing loss (> 25 dB HL in one or both ears across frequencies) was evident in 85.5% of patients' posttreatment, compared with 47.8% of patients across conventional frequencies. EHF audiometry demonstrated an ototoxic shift (American Speech-Language-Hearing Association criteria) in 56.5% of cases compared with 31.9% when only conventional audiometry was considered. Mean hearing deterioration for patients was significant across EHFs (9-16 kHz) bilaterally (p < .05). Absent EHF thresholds at the initial assessment, owing to maximum output limits, was a limitation that occurred most frequently at 16 kHz (17.4%, 24/138).

CONCLUSIONS

EHF audiometry is most sensitive for the early detection of ototoxicity and should be included in monitoring programs. Clinical ototoxicity monitoring protocols should consider shortened assessment approaches that target frequencies most sensitive to ototoxicity, including EHFs.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.21651242.

Ototoxicity of Topical Antibiotic Ear Drops in Chronic Suppurative Otitis Media in Humans: A Review of the Literature

An electronic search of the literature was performed for reported cases of ototoxicity associated with the use of topical antibiotic ear drops in humans. The dosage, duration, and type of ototoxic preparations involved were recorded. Due to the scant quantity of low-quality information that is currently available, there was uncertainty about the usefulness of topical antibiotics in enhancing the resolution of ear discharge in patients with chronic suppurative otitis media. However, despite this uncertainty, there are some data to show that using topical antibiotics in comparison to a placebo or in conjunction with a systemic antibiotic may be useful. Additionally, there is ambiguity regarding the relative efficacy of various kinds of antibiotics; it is impossible to say with absolute certainty whether quinolones are superior to or inferior to aminoglycosides. Although the adverse impact profiles of these two classes of chemicals varied, there are not enough data from the included trials to draw any conclusions about them. Negative effects were generally underreported.

Ototoxicity of Artemisinin-Based Combination Therapy: A Case Presentation

Neuroauditory-toxicity should always be borne in mind prior to treatment of severe conditions like cerebral-malaria and due attention should be paid to auditory monitoring. Artemisinin-based combination therapy is the best available treatment for cerebral malaria however its attribution to hearing loss remains undetermined. This report manifests ototoxic effect of artemisinin.

Changes in vestibular and cochlear function following platinum-based chemotherapy: A preliminary report

OBJECTIVES

This study investigated the changes in vestibular and cochlear function in patients receiving platinum-based chemotherapy.

METHODS

A longitudinal study of 32 participants (10-70 years) receiving chemotherapy participated in the study. Baseline and exit vestibular and hearing assessments that included video head impulse (VHIT) testing, cervical and ocular vestibular evoked myogenic potentials (VEMP), dynamic visual acuity (DVA) and pure-tone audiometry were performed at the patient's treatment venue.

RESULTS

Half (50%) of the participants showed cochleotoxicity from baseline to exit testing, with left ears significantly more affected than right ears. There was no consistent relationship between hearing loss and vestibular dysfunction. DVA yielded normal results at baseline and exit testing in all participants. VEMP responses were absent in 28.1% of participants at baseline, reflecting the challenges of using VEMP for monitoring. VEMP and VHIT results showed a statistically significant (p < 0.05) decline in results from baseline to exit testing; however, participants did not report symptoms related to vestibular dysfunction. VHIT also showed left ears significantly (p < 0.05) more affected than right ears.

CONCLUSION

VHIT proved to be a valuable measure of changes in vestibular function secondary to ototoxicity. Future investigations should determine vestibulotoxicity criteria and optimal protocols for vestibulotoxicity monitoring at the patient's treatment venue.

Coexposure to Solvents and Noise as a Risk Factor for Hearing Loss in Agricultural Workers

OBJECTIVE

This study addressed the relationship of hearing loss and coexposure to solvents and noise among farmers and ranchers in central United States.

METHODS

The surveillance study included surveys to stratified random samples of operations in 2018 and 2020 (n = 34,146), requesting information on injuries, illnesses, exposures, and preventive measures. Responses (n = 7495) were analyzed using hierarchical multinomial logistic regression, adjusting for personal and work characteristics.

RESULTS

Nearly 60% of respondents exposed to both solvents and noise reported hearing loss. The exposures increased the adjusted odds of moderate/severe hearing loss as follows: solvents alone, (odds ratio [OR], 1.49; 95% confidence interval [CI], 0.93-2.38), noise alone (OR, 4.42; 95% CI, 3.39-5.76), and coexposure to both noise and solvents (OR, 6.03; 95% CI, 4.67-7.78).

CONCLUSIONS

Solvent exposure, along with noise, should be considered in hearing conservation programs among farmers and ranchers.

Validity of automated audiometry for hearing examination in patients with multidrug-resistant tuberculosis

Background: The objective of this study was to test the validity of automated audiometry as a method of hearing examination in patients with multidrug-resistant tuberculosis.

Methods: This was a cross-sectional comparative study with a retrospective approach, using patient medical records. Patients with multidrug-resistant tuberculosis (MDR-TB) were recruited based-on medical records that met the inclusion and exclusion criteria at the Pulmonology outpatient unit, then referred to the Otorhinolaryngology outpatient unit of the Dr. Soetomo Academic Medical Center. The subjects’ hearing function was measured with two different devices (automated audiometer and conventional audiometer) before being given anti-tuberculosis drug therapy (aminoglycoside injection) as ototoxicity monitoring from July to December 2019 period. Sensitivity and specificity analysis was used to assess the validity of the test.

Results: A total of 36 patients (72 ears) were included. The comparison test results using the Mann-Whitney test showed that there were significant differences between automated audiometry and conventional audiometry in both ears. Analysis values were: sensitivity 80-97%, specificity 37-96%, positive predictive value 74-98%, and negative predictive value 59-96%.

Conclusions: Automated audiometry is valid for use as a method of hearing examination and monitoring in patients with multidrug-resistant tuberculosis.

Ototoxicity in childhood: Recommendations of the CODEPEH (Commission for the Early Detection of Childhood Hearing Loss) for prevention and early diagnosis

Ototoxicity is defined as the damage, reversible or irreversible, produced in the inner ear by various substances that are called ototoxic and that can cause hearing loss and/or an alteration of the vestibular system. Permanent hearing loss significantly affects quality of life and is especially important in children. The lack or delay in its detection is frequent, since it often progresses in an inconspicuous manner until it affects communication and overall development. This impact can be minimized by following a strategy of audiological monitoring of ototoxicity, which allows for its early detection and treatment. This document recommends that children who are going to be treated with cisplatin or aminoglycosides be monitored. This CODEPEH review and recommendation document focuses on the early detection, prophylaxis, otoprotection, monitoring and treatment of ototoxicity caused by aminoglycosides and platinum-based antineoplastics in the paediatric population.

Cisplatin-associated ototoxicity: perspectives from a single institution cervical cancer cohort and implications for developing a locally responsive monitoring programme in a public healthcare setting

Background

Ototoxicity monitoring is uncommon in South Africa, despite the increased use of ototoxic medication to manage the burden of disease in the country. The successful implementation of such a protocol requires cognisance of contextual realities and multiple dimensions for consideration from both patients and service providers. As part of an ongoing cohort study on cisplatin-associated ototoxicity and efforts to better inform the implementation of such programmes, the perspectives of cervical cancer patients and healthcare workers towards ototoxicity monitoring were assessed.

Methods

This concurrent-triangulation mixed-methods study was conducted at a tertiary hospital in South Africa. Self-reported questionnaires from patients (n = 80) and healthcare personnel comprising clinicians, oncology nurses, pharmacists, and radiotherapists (n = 32), results of audiological evaluations, researcher field notes, and estimated patient and service provider costs contributed to data for this study. Data analysis included descriptive statistics, comparison of test characteristics and deductive thematic analysis.

Results

The ototoxicity monitoring programme was positively received by the participants, with 90.6% of healthcare personnel and 89% of patients reporting it to be beneficial. The clinicians (76.6%) were identified as the main providers of information on the effects of chemotherapy medication and made the necessary referrals for audiological evaluation. The approximate cost of setting up such a programme included purchase of equipment (US56 700) and the appointment of an audiologist (US 26 250). The approximate costs to patients included transport costs (US$ 38) and the loss of income for the day (US 60), calculated at the minimum wage per hour, if employed. Creative appointment scheduling, easy facility access and detailed locally comprehensible couselling improved patient compliance to the programme. Whilst the sequential use of American Speech-Language-Hearing Association (ASHA) and National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) criteria aided in an evidence-informed approach to aural rehabilitation, DPOAEs and speech discrimination displayed low sensitivity (range 1.45% – 22.39%) but high specificity (range 77.78% – 100%) when identifying ototoxic change.

Conclusion

This novel study, through a ‘real-world’ experience, has revealed that an ototoxicity monitoring programme is feasible in South Africa, through meaningful engagements with- and considerations from- patients and service providers regarding planning, delineation of responsibilities and cost implications. The findings can potentially serve as a roadmap for other limited resource environments.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12913-022-08099-8.

Cichoric Acid May Play a Role in Protecting Hair Cells from Ototoxic Drugs

Ototoxic hearing loss due to antibiotic medication including aminoglycosides and excess free radical production causes irreversible hair cell injury. Cichoric acid, a naturally occurring phenolic acid, has recently been found to exert anti-oxidative and anti-inflammatory properties through its free radical scavenging capacity. The present study aimed to investigate the protective effects of cichoric acid against neomycin-induced ototoxicity using transgenic zebrafish (pvalb3b: TagGFP). Our results indicated that cichoric acid in concentrations up to 5 μM did not affect zebrafish viability during the 2 h treatment period. Therefore, the otoprotective concentration of cichoric acid was identified as 5 μM under 2 h treatment by counting viable hair cells within the neuromasts of the anterior- and posterior-lateral lines in the study. Pretreatment of transgenic zebrafish with 5 μM of cichoric acid for 2 h significantly protected against neomycin-induced hair cell death. Protection mediated by cichoric acid was, however, lost over time. A terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay and FM4-64 staining, respectively, provided in situ evidence that cichoric acid ameliorated apoptotic signals and mechanotransduction machinery impairment caused by neomycin. A fish locomotor test (distance move, velocity, and rotation frequency) assessing behavioral alteration after ototoxic damage revealed rescue due to cichoric acid pretreatment before neomycin exposure. These findings suggest that cichoric acid in 5 μM under 2 h treatment has antioxidant effects and can attenuate neomycin-induced hair cell death in neuromasts. Although cichoric acid offered otoprotection, there is only a small difference between pharmacological and toxic concentrations, and hence cichoric acid can be considered a rather prototypical compound for the development of safer otoprotective compounds.

Urinary phenols and parabens in relation to hearing loss: The National Health and Nutrition Examination Survey

INTRODUCTION

The animal studies raise concerns about the possible ototoxicity of phenolic chemicals. Therefore, we conducted an epidemiologic study to examine the associations of phenols and parabens with hearing impairment.

MATERIALS AND METHODS

Bisphenol A (BPA), benzophenone-3 (BP-3), and triclosan (TCS) were measured in urine samples in the National Health and Nutrition Examination Survey (NHANES) 2003-06 and 2009-12. Methyl paraben (MPB) and propyl paraben (PPB) were measured in urine samples in NHANES 2005-06 and 2009-12. Hearing impairment was defined as a hearing threshold of more than 25 dB at each hearing frequency in the better ear. Tests for linear trend were conducted using the median concentrations of urinary phenols or parabens in each quartile as a continuous variable.

RESULTS

A total of 1809 participants (women = 52.0%) aged 20 and above were included in the final analysis (For MPB and PPB, the sample size was 1188). After adjusting for potential confounders, we found positive associations between BPA and hearing impairment at 3 K (p-trend = 0.04); between TCS and hearing impairment at 6 K (p-trend = 0.03); However, the odds ratio (OR) for the highest compared with the lowest quartile of both BPA and TCS did not reach statistical significance. In contrast, we found unexpected negative associations between BP-3 and hearing impairment at 0.5 K (p-trend = 0.04), 1 K (p-trend = 0.02), 2 K (p-trend <0.01), 6 K (p-trend = 0.03), and 8 K Hz (p-trend = 0.02), respectively.

CONCLUSIONS

The present study offers limited evidence that background phenol and paraben exposures are ototoxicants for the United States adult population.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40201-021-00779-7.

Adverse Audio-Vestibular Effects of Drugs and Vaccines Used in the Treatment and Prevention of COVID-19: A Review

(1) Background: The purpose of this article is to review pharmacological treatments for COVID-19 (currently approved by the EMA (European Medical Agency) and FDA (Food and Drug Administration)) and highlight their potential audio-vestibular side-effects as an ototoxic adverse reaction. (2) Methods: Review of the available literature in the scientific databases PubMed, ResearchGate, Scopus, and ScienceDirect, and in summaries of product data sheets. (3) Results: In accordance with EBM (evidence-based medicine) the treatment of COVID-19 by using lopinavir/ritonavir, chloroquine and hydroxychloroquine, azithromycin, favipiravir, amantadine, oseltamivir, and ivermectin is no longer recommended for patients suffering from COVID-19 due to a lack of clinical data, publications, and recommendations. There were 39 publications and 15 summaries of product characteristics (as other sources of data) which were also used in this analysis. Adverse events could be permanent or disappear over time. Following treatment for COVID-19, the most frequent adverse audio-vestibular reactions reported in clinical trials and publications in the area of audiology and otorhinolaryngology were: dizziness, blurry vision with dizziness, nasopharyngitis, dysgeusia, and tinnitus. As far as vaccines are concerned, dizziness as an ototoxic effect was uncommon and occurs only in hypersensitive people who experience anaphylactic shock. (4) Conclusions: The ototoxicity of the drugs discussed here does not have as severe symptoms as the drugs used in the treatment of COVID-19 in 2020 (e.g., hydroxychloroquine), and relates mainly to disorders of the vestibulocochlear system. However, there is still a need to monitor ototoxic side-effects because of potential interactions with other ototoxic drugs. Many of the drugs approved by EMA and FDA are new, and not every side-effect is known.

A longitudinal community-based ototoxicity monitoring programme and treatment effects for drug-resistant tuberculosis treatment, Western Cape

Background

South Africa has a high burden of drug-resistant tuberculosis (DRTB) and until recently, ototoxic aminoglycosides were predominant in treatment regimens. Community-based ototoxicity monitoring programmes (OMPs) have been implemented for early detection of hearing loss and increased patient access.

Objectives

A longitudinal study was conducted to describe the service delivery characteristics of a community-based OMP for DRTB patients facilitated by CHWs as well as observed ototoxic hearing loss in this population.

Method

A descriptive retrospective record review of longitudinal ototoxicity monitoring of 194 DRTB patients undergoing treatment at community-based clinics in the city of Cape Town between 2013 and 2017.

Results

Follow-up rates between consecutive monitoring assessments reached as high as 80.6% for patients assessed by CHWs. Few patients (14.2% – 32.6%) were assessed with the regularity (≥ 6 assessments) and frequency required for effective ototoxicity monitoring, with assessments conducted, on average, every 53.4–64.3 days. Following DRTB treatment, 51.5% of patients presented with a significant ototoxic shift meeting one or more of the American Speech-Language-Hearing Association (ASHA) criteria. Deterioration in hearing thresholds was bilateral and most pronounced at high frequencies (4 kHz – 8 kHz). The presence of pre-existing hearing loss, human immunodeficiency virus co-infection and a history of noise exposure were significant predictors of ototoxicity in patients.

Conclusion

DRTB treatment with kanamycin resulted in significant deterioration of hearing longitudinally, predominantly at high frequencies. With ongoing training and supportive supervision, CHWs can facilitate community-based ototoxicity monitoring of DRTB patients. Current protocols and guidelines may require reassessment for appropriate community-based ototoxicity monitoring.

Hearing and Vestibular Loss with Misuse of Opioids and Illicit Drugs: A Review of the Literature

BACKGROUND

The purpose of this review was to summarize the literature regarding the effects of opioids and illicit drugs on the auditory and vestibular systems.

METHODS

Data were sourced from published papers reporting hearing loss (HL) and/or vestibular loss (VL) following misuse or overdose of opioids or illicit drugs. Most papers consisted of retrospective single-case reports, with few retrospective reviews or prospective cohort studies. Search terms included variations of HL, VL, opioids, and illicit drugs. Search results yielded 51 articles published between 1976 and 2021. A total of 44 articles were reviewed after excluding studies that were not available in English (n = 3), only described acute effects in healthy cohorts (n = 3) or only described general health aspects in a group on methadone maintenance (n = 1).

RESULTS

Sixteen studies reported ototoxicity from illicit drugs, 27 from prescription opioids, and 1 was unspecified. This review shows that HL associated with amphetamines and cocaine was typically sudden, bilateral, and temporary. HL from cocaine/crack and heroin often presented with greatest losses in the mid-frequency range. HL associated with opioids was typically sudden, bilateral, moderately severe to profound, and in most cases permanent. The literature is sparse regarding VL from illicit drugs and opioids.

CONCLUSION

Practitioners who see patients for sudden or rapidly progressive HL or VL with no apparent cause should inquire about misuse of illicit drugs and opioids, particularly when the HL does not respond to steroid treatment.

Ototoxicity monitoring in South African cancer facilities: A national survey

Background

National information regarding ototoxicity monitoring practices are limited for patients undergoing chemotherapy in South Africa.

Objectives

To determine (1) the national status of ototoxicity monitoring implemented in private and public cancer facilities, (2) the knowledge and ototoxicity monitoring approaches implemented, and (3) reported challenges.

Method

A descriptive quantitative survey was conducted in public and private oncology units and audiology referral clinics. Private (60%) and public (43%) oncology units that provide platinum-based chemotherapy in South Africa and audiology referral units (54%) were: (1) surveyed telephonically to determine if ototoxicity monitoring takes place; and (2) a self-administered survey was sent to qualifying oncology units and audiology referral clinics.

Results

All public oncology units reported that ototoxicity monitoring only occurs on referral and is not standard practice. All private oncology units indicated that monitoring is on a patient self-referral basis when symptoms occur. Poor awareness of ototoxicity monitoring best practice guidelines was reported by all oncology units and 14% of audiology referral clinics. Audiology referral clinics reported adequate knowledge of ototoxicity protocols although they are not widely used with only 43% following best practice guidelines. The most prominent challenges reported by participants was referral system (67% oncology units; 57% audiology referral clinics), environmental noise (83% oncology units; 86% audiology referral clinics) and the compromised status of cancer patients (67% oncology units; 57% audiology referral clinics).

Conclusion

Ototoxicity monitoring is not routinely implemented across oncology units in South Africa. Multidisciplinary teamwork and a simplified national ototoxicity monitoring protocol may improve hearing outcomes for patients.

Medication Use Reported by Individuals With Tinnitus Who Are Seeking Internet-Based Psychological Interventions

PURPOSE

This study examined medication use by individuals with tinnitus who were seeking help for their tinnitus by means of a psychological intervention.

METHOD

This study used a cross-sectional survey design and included individuals with tinnitus enrolled in an Internet-based cognitive behavioral therapy trial (n = 439). Study participants provided demographic details, completed various structured questionnaires and provided details about the medications used. The self-reported medications were classified using the United States Pharmacopeial Medicare Model Guidelines v7.0.

RESULTS

Current medication use was reported by 67% (n = 293) of the study participants. Those currently using medication were older; had consulted their primary care physician, had greater tinnitus severity, depression, anxiety, and insomnia when compared with those not reporting any current medication use. The top 10 medication used included cardiovascular agents (n = 162; 55.3%), antidepressants (n = 80; 27.3%), electrolytes/minerals/metals/vitamins (n = 70; 23.9%), respiratory tract/pulmonary agents (n = 62; 21.2%), anxiolytics (n = 59; 20.1%), hormonal agents/stimulant/replacement/modifying (thyroid; n = 45; 15.4%), gastrointestinal agents (n = 43; 14.7%), analgesics (n = 33; 11.3%), blood glucose regulators (n = 32; 10.9%), and anticonvulsants (n = 26; 8.87%). Some associations between type of medication used and demographic or tinnitus-related variables were noted especially for the cardiovascular agents, electrolytes/minerals/metals/vitamins, and anxiolytics.

CONCLUSIONS

This exploratory study indicated a large percentage of patients using medication and a range of medications. Further studies are required to assess the effects of such medications on the tinnitus percept and concurrent medication moderate treatment effects.

Protective effect of berberine chloride against cisplatin-induced ototoxicity

Background

Cisplatin (CP) is an effective anticancer drug broadly used for various types of cancers, but it has shown ototoxicity that results from oxidative stress. Berberine has been reported for its anti-oxidative stress suggesting its therapeutic potential for many diseases such as colitis, diabetes, and vascular dementia.

Objective

Organ of Corti of postnatal day 3 mouse cochlear explants were used to compare hair cells after the treatment with cisplatin alone or with berberine chloride (BC) followed by CP.

Methods

We investigated the potential of the anti-oxidative effect of BC against the cisplatin-induced ototoxicity. We observed a reduced aberrant bundle of stereocilia in hair cells in CP with BC pre-treated group. Caspase-3 immunofluorescence and TUNEL assay supported the hypothesis that BC attenuates the apoptotic signals induced by CP. Reactive oxygen species level in the mitochondria were investigated by MitoSOX Red staining and the mitochondrial membrane potentials were compared by JC-1 assay.

Results

BC decreased ROS generation with preserved mitochondrial membrane potentials in mitochondria as well as reduced DNA fragmentation in hair cells. In summary, our data indicate that BC might act as antioxidant against CP by reducing the stress in mitochondria resulting in cell survival.

Conclusion

Our result suggests the therapeutic potential of BC for prevention of the detrimental effect of CP-induced ototoxicity.

Bile acid-permeation enhancement for inner ear cochlear drug - pharmacological uptake: bio-nanotechnologies in chemotherapy-induced hearing loss

Ototoxicity is the damage to inner ear sensory epithelia due to exposure to certain medications and chemicals. This occurs when toxins enter the tightly controlled inner ear environment inducing hair cell death, resulting in hearing loss. Recent studies have explored hydrogel-based bio-nanotechnologies and new drug delivery formulations to prevent drug-induced hearing loss, with much attention given to administration of antioxidant drugs. Bile acids have been recognized as promising excipients due to their biocompatibility and unique physiochemical properties. As yet bile acids have not been explored in improving drug delivery to the inner ear despite improving drug stability and delivery in other systems and demonstrating positive biological effects in their own right.

Community-Based Ototoxicity Monitoring for Drug-Resistant Tuberculosis in South Africa: An Evaluation Study

In response to the drug-resistant tuberculosis (DRTB) ototoxicity burden in South Africa, ototoxicity monitoring has been decentralised, with community health workers (CHWs) acting as facilitators. This study describes a community-based ototoxicity monitoring programme (OMP) for patients with DRTB. Findings are compared to the recommended guidelines for ototoxicity monitoring, the OMP protocol and published studies. This was a retrospective study of longitudinal ototoxicity monitoring of 831 patients with DRTB, using data collected at community-based clinics in the City of Cape Town between 2013 and 2017. Approximately half (46.8%) of the patients had an initial assessment conducted in accordance with the OMP protocol recommendations, and follow-up rates (79.5%) were higher than those of a similar DRTB programme. However, patients in this study were not monitored within the timeframes or with the regularity recommended by the guidelines or the OMP protocol. Extended high-frequency pure-tone audiometry (27.5%) was underutilised by testers and data recording was inconsistent (e.g., 37.7% of patient gender was not recorded by testers). Community-based OMP using CHWs to facilitate monitoring showed improvement over previous hospital-based reports, with more accessible services and higher follow-up rates. However, to improve OMP outcomes, OMP managers should reassess current protocols and data recording practices.

Chemotherapy-induced hearing loss: the applications of bio-nanotechnologies and bile acid-based delivery matrices

Advancement in the prevention of chemotherapy-induced hearing loss has proposed new nano-based delivery matrices that can target inner ear regions most damaged by chemotherapy. Chemotherapy agents (e.g., cisplatin) induce increased reactive oxygen species formation in the inner ear that damage sensory hair cells and result in irreversible hearing impairment. Exogenous antioxidants (e.g., Probucol and metformin) have been shown to block the formation of these reactive oxygen species. Delivery of these drugs in effective concentrations remains a challenge. Microencapsulation in combination with drug excipients provides one technique to effectively deliver these drugs. This paper investigates the use of probucol and metformin in combination with drug excipients for novel, inner ear, delivery.

Fused deposition modelling 3D printing proof-of-concept study for personalised inner ear therapy

OBJECTIVES

There is a requirement within ear therapeutics for a delivery system capable of safely delivering controlled doses to the inner ear. However, the anatomy and sensitivity of the inner ear make current delivery systems problematic and often ineffective. Therefore, a new delivery system is required to overcome these issues and provide a more efficacious system in the treatment of inner ear disease. This study assesses the potential of 3D printing (3DP) as a fabrication method for an implantable drug delivery system (DDS) to the inner ear.

KEY FINDINGS

Three implantable designs of varying geometry were produced with fused deposition modelling (FDM) 3DP, each loaded with 0.25%, 0.5% and 1% levofloxacin; filaments prepared by hot-melt extrusion. Each implant was effective in providing sustained, therapeutic release of levofloxacin for at least 4 days and as such would be effective in therapeutic treatment of many common inner ear diseases, such as otitis media or Ménière's disease.

CONCLUSIONS

This proof-of-concept research was successful in utilising FDM as a fabrication method for a DDS capable of providing prolonged release directly to the inner ear and highlights the viability of 3DP in the fabrication of an inner ear DDS.

Recommendations for Age-Appropriate Testing, Timing, and Frequency of Audiologic Monitoring During Childhood Cancer Treatment: An International Society of Paediatric Oncology Supportive Care Consensus Report

Importance

Ototoxicity is an irreversible direct and late effect of certain childhood cancer treatments. Audiologic surveillance during therapy as part of the supportive care pathway enables early detection of hearing loss, decision-making about ongoing cancer treatment, and, when applicable, the timely use of audiologic interventions. Pediatric oncologic clinical practice and treatment trials have tended to be driven by tumor type and tumor-specific working groups. Internationally accepted standardized recommendations for monitoring hearing during treatment have not previously been agreed on.

Objective

To provide standard recommendations on hearing loss monitoring during childhood cancer therapy for clinical practice.

Methods

An Ototoxicity Task Force was formed under the umbrella of the International Society of Paediatric Oncology, consisting of international audiologists, otolaryngologists, and leaders in the field of relevant pediatric oncology tumor groups. Consensus meetings conducted by experts were organized, aimed at providing standardized recommendations on age-directed testing, timing, and frequency of monitoring during cancer treatment based on literature and consensus. Consensus statements were prepared by the core group, adapted following several videoconferences, and finally agreed on by the expert panel.

Findings

The consensus reached was that children who receive ototoxic cancer treatment (platinum agents, cranial irradiation, and/or brain surgery) require a baseline case history, monitoring of their middle ear and inner ear function, and assessment of tinnitus at each audiologic follow-up. As a minimum, age-appropriate testing should be performed before and at the end of treatment. Ideally, audiometry with counseling before each cisplatin cycle should be considered in the context of the individual patient, specific disease, feasibility, and available resources.

Conclusions and Relevance

This is an international multidisciplinary consensus report providing standardized supportive care recommendations on hearing monitoring in children undergoing potentially ototoxic cancer treatment. The recommendations are intended to improve the care of children with cancer and facilitate comparative research on the timing and development of hearing loss caused by different cancer treatment regimens.

Detection of unknown ototoxic adverse drug reactions: an electronic healthcare record-based longitudinal nationwide cohort analysis

Ototoxic medications can lead to significant morbidity. Thus, pre-marketing clinical trials have assessed new drugs that have ototoxic potential. Nevertheless, several ototoxic side effects of drugs may remain undetected. Hence, we sought to retrospectively investigate the potential risk of ototoxic adverse drug reactions among commonly used drugs via a longitudinal cohort study. An electronic health records-based data analysis with a propensity-matched comparator group was carried out. This study was conducted using the MetaNurse algorithm for standard nursing statements on electronic healthcare records and the National Sample Cohort obtained from the South Korea National Health Insurance Service. Five target drugs capable of causing ototoxic adverse drug reactions were identified using MetaNurse; two drugs were excluded after database-based analysis because of the absence of bilateral hearing loss events in patients. Survival analysis, log-rank test, and Cox proportional hazards regression models were used to calculate the incidence, survival rate, and hazard ratio of bilateral hearing loss among patients who were prescribed candidate ototoxic drugs. The adjusted hazard ratio of bilateral hearing loss was 1.31 (1.03–1.68), 2.20 (1.05–4.60), and 2.26 (1.18–4.33) in cimetidine, hydroxyzine, and sucralfate users, respectively. Our results indicated that hydroxyzine and sucralfate may cause ototoxic adverse drug reactions in patients. Thus, clinicians should consider avoiding co-administration of these drugs with other well-confirmed ototoxic drugs should be emphasized.

Association of beta blocker use and hearing ability in adults: a cross-sectional study

OBJECTIVES

To investigate the potential association between beta blocker use and hearing ability in adults and to discern whether this effect is dose-dependent.

DESIGN

Cross-sectional analyses. Multiple linear regression was performed with hearing ability as the dependent variable and beta blocker use as the independent variable. The independent variable was classified into three dose categories for secondary analysis. Adjustments were made for age, gender, educational level, and tobacco smoking status.

STUDY SAMPLE

1636 adults, 75 of whom reported being on beta blockers, from the internet-based Netherlands Longitudinal Study on Hearing (NL-SH).

RESULTS

No significant association was found between beta blocker use and hearing ability in noise. In the adjusted regressions, beta blocker use changed the speech reception threshold in noise (SRT) by -0.04 dB signal-to-noise ratio (SNR) (95%CI [-0.67 to 0.58], p = 0.890). Medium dose beta blocker use changed SRT by -0.42 dB SNR (95%CI [-1.38 to 0.71], p = 0.433), while a high dose changed it by -0.26 dB SNR (95%CI [-1.74 to 1.4], p = 0.767).

CONCLUSIONS

No evidence was found for beta blocker-induced changes in hearing ability. Future studies on this topic should favour case-control and cohort study designs, while focussing on a hypertensive population to minimise confounding by indication.

Insight into the current practice of ototoxicity monitoring during cisplatin therapy

Background

The aim of this study is to evaluate the current state of ototoxicity monitoring for patients receiving cisplatin chemotherapy in an academic medical center with particular attention to how closely monitoring adheres to national ototoxicity guidelines.

Methods

Case series including retrospective medical records review of patients (age > 18) treated with cisplatin at University of California Davis Medical Center between January 2014 and August 2017. Patient and ototoxicity related variables were analyzed. Patients that underwent a transfer of care during treatment and with less than 3 months of follow-up were excluded.

Results

Three hundred seventy-nine patients met study criteria, of which 104 (27.4%) had a prior history of hearing loss. Prior to treatment, 196 (51.7%) patients were counseled regarding the ototoxic nature of cisplatin and 92 (24.3%) patients had a pretreatment audiogram. During treatment, 91 (24%) patients had documented otologic complaints. Only 17 patients (4.5%) patients had an audiogram ordered during their cisplatin treatment period. 130 (34.3%) patients had otologic complaints following cisplatin treatment. Audiograms were ordered for 20 (7.8%), 13 (5.1%), and 16 (6.2%) patients at 1-month, 3-month, and 6-month follow-ups, respectively. No patients in the study cohort received baseline, treatment, and post-treatment audiograms as recommended by national ototoxicity monitoring protocols. Patients with Head and Neck Cancer (HNC) represented the largest subgroup that received cisplatin (n = 122, 32.2%) and demonstrated higher rates of ototoxicity counseling (n = 103, 84.4%) and pretreatment audiograms (n = 70, 57.4%) compared to the non HNC group (n = 36, 36.2%, P < 0.0001 and n = 22, 8.5%, P < 0.0001).

Conclusions

There is poor adherence to national ototoxicity monitoring guidelines at a large academic medical center. This is a missed opportunity for intervention and aural rehabilitation. Improved education and collaboration between otolaryngology, audiology, and medical oncology is needed to develop and promote an effective ototoxicity-monitoring program.

Graphical abstract

Drug-Induced Hearing Loss in Children: An Analysis of Spontaneous Reports in the French PharmacoVigilance Database

INTRODUCTION

Hearing loss can have a negative impact on communication, with significant vocational, educational, and social consequences. Drugs are one of the causes of hearing loss in children.

OBJECTIVES

The objective of our study was to describe drug-induced hearing loss in the pediatric population.

METHODS

Reports of hearing loss from 1985 to December 2019 in the pediatric population (< 18 years) were extracted from the French PharmacoVigilance Database (FPVD). We performed a retrospective and descriptive analysis of adverse drug reaction (ADR) reports.

RESULTS

A total of 70 ADR reports were identified among the 51,216 reports registered in the FPVD, 37 involving adolescents (12-17 years, 52.9%), 28 children (2-11 years, 40.0%), and 5 infants (28 days-23 months, 7.1%). Overall, 40 reports (57.1%) involved girls. A total of 56 reports (80.0%) were "serious." The most frequent hearing disorders were deafness (n = 31, 44.3%) and hypoacusis (n = 22, 31.4%). Suspected drugs (ATC 5th level) were amikacin (n = 11, 15.7%), cisplatin (n = 11, 15.7%), doxorubicin (n = 4, 5.7%), vincristine (n = 4, 5.7%), clarithromycin (n = 4, 5.7%), ceftriaxone (n = 3, 4.3%), isotretinoin (n = 3, 4.3%), and vancomycin (n = 3, 4.3%).

CONCLUSIONS

This study shows that about three out of four cases of drug-induced hearing loss in the pediatric population were "serious". It also underlines the under-reporting of these ADRs and the importance of strengthening hearing monitoring in children during and long after drug exposure.

Genetic Inheritance and Its Contribution to Tinnitus

Tinnitus is the abnormal perception of sound that affects more than 15% of adult population around the globe. Severe tinnitus is considered a complex disorder that arises as result of the interaction of genetic and environmental factors, and it is associated with several comorbidities such as hearing loss, anxiety, and insomnia. We begin this review with an introduction to human molecular genetics and the role of genetic variation on the inheritance. There are some genetic reports on tinnitus heritability including concordance studies in twins and adoptees or aggregation in families providing some evidence for familial aggregation in patients with severe tinnitus and high concordance in monozygotic twins with bilateral tinnitus. So, sex differences in familial aggregation and heritability of bilateral tinnitus suggest a potential sexual dimorphism in tinnitus inheritance.Molecular genetic studies have been demonstrated to be a useful tool to understand the role of genetic variation in rare diseases and complex disorders. The reported associations in common variants in neurotrophic factors such as GDNF, BDNF, or potassium channels genes were underpowered, and the lack of replication questions these findings. Although candidate gene approaches have failed in replicating these genetic associations, the development of high throughput sequencing technology and the selection of extreme phenotypes are strategies that will allow the clinicians and researchers to combine genetic information with clinical data to implement a personalized diagnosis and therapy in patients with tinnitus.

In Pursuit of Preventive Audiology in South Africa: Scoping the Context for Ototoxicity Assessment and Management

Aim

The study explored the South African healthcare context for ototoxicity assessment and management from the audiologists' perspectives.

Materials and Methods

This was done through a survey research methodology that adopted a cross-sectional research design. South African audiologists were recruited from professional associations databases using specific inclusion criteria; and 31 audiologists from across the country participated. The study used an 18-item web-based survey guided by the Health Professions Council of South Africa (HPCSA) (2018) guidelines. Data were analyzed through both descriptive and inferential statistics.

Results

Findings revealed serious contextual challenges influencing the implementation of assessment and management programs within the South African context. Over two-thirds of the participants engage with ototoxicity monitoring and management, but the practices adopted are not aligned to international standards nor the national HPCSA guidelines on assessment and management of patients on ototoxic medications. Findings speak to the frequency of practice; the referral pathways audiologists use; prevention and promotion methods used; availability of resources for the implementation of ototoxicity assessment and management; barriers to ototoxicity assessment and management; the influence of language and culture in ototoxicity assessment and management; as well as information management practices within this context. No relationship could be established between knowledge regarding ototoxicity, communication, caseload, and ototoxicity assessment and management on the chi-square.

Conclusion

Implications for strategic planning, budget allocation, collaborative multidisciplinary within the same institution approaches; training; policy formulation; and translation of policies and guidelines into practice are raised by these findings.

Building inner ears: recent advances and future challenges for in vitro organoid systems

While inner ear disorders are common, our ability to intervene and recover their sensory function is limited. In vitro models of the inner ear, like the organoid system, could aid in identifying new regenerative drugs and gene therapies. Here, we provide a perspective on the status of in vitro inner ear models and guidance on how to improve their applicability in translational research. We highlight the generation of inner ear cell types from pluripotent stem cells as a particularly promising focus of research. Several exciting recent studies have shown how the developmental signaling cues of embryonic and fetal development can be mimicked to differentiate stem cells into “inner ear organoids” containing otic progenitor cells, hair cells, and neurons. However, current differentiation protocols and our knowledge of embryonic and fetal inner ear development in general, have a bias toward the sensory epithelia of the inner ear. We propose that a more holistic view is needed to better model the inner ear in vitro. Moving forward, attention should be made to the broader diversity of neuroglial and mesenchymal cell types of the inner ear, and how they interact in space or time during development. With improved control of epithelial, neuroglial, and mesenchymal cell fate specification, inner ear organoids would have the ability to truly recapitulate neurosensory function and dysfunction. We conclude by discussing how single-cell atlases of the developing inner ear and technical innovations will be critical tools to advance inner ear organoid platforms for future pre-clinical applications.

Protective Effect of Carvacrol against Paclitaxel-Induced Ototoxicity in Rat Model

Objective

This study aimed to explore whether carvacrol (CV) had a protective effect on paclitaxel-induced ototoxicity from biochemical, functional, and histopathological perspectives.

Methods

Forty Wistar albino male rats were randomly separated into five groups of eight rats. Group 1 was the control group, so Paclitaxel or CV was not administered. Group 2 was administered i.p. CV at 25 mg/kg once a week; Group 3, was administered i.p. paclitaxel at 5 mg/kg once a week; Group 4 was administered i.p. paclitaxel at 5 mg/kg followed (30 min later) by CV at 25 mg/kg once a week; and Group 5 was administered i.p. CV at 25 mg/kg followed (1 day later) by paclitaxel at 5 mg/kg. once a week. The drugs were administered intraperitoneally once a week for four consecutive weeks, and distortion product otoacoustic emissions (DPOAE) tests were performed at the beginning of the study before the first drug administration and at the end of the study after the last drug administration. All rats were sacrificed, and cochleae were removed for biochemical and histopathological analysis.

Results

Biochemical data indicated that paclitaxel caused oxidative stress in the cochlea. Histopathological findings revealed the loss of outer hair cells in the organ of Corti (CO) and moderate degenerative changes in the stria vascularis (SV). It was observed that DPOAE measurements were significantly reduced at high frequencies. In groups which CV was administered together with paclitaxel, these biochemical, histopathological, and functional changes were favorably reversed.

Conclusion

CV may have a protective effect against paclitaxel-induced ototoxicity when given.

Drug-Induced Ototoxicity: A Comprehensive Review and Reference Guide

OBJECTIVE

In an era of increasing polypharmacy, adverse drug effects such as ototoxicity have significant public health implications. Despite the availability of evidence, many health care professionals may not know the risk of ototoxicity in common medications. Therefore, the aim of this review is to provide a comprehensive, easy to use, ototoxic profile of medications with an assessment of supporting evidence.

METHODS

Medications of interest were identified through adverse drug reaction reports derived from Micromedex (IBM), Lexicomp (Wolters Kluwer), and the textbook, Drug Induced Diseases: Prevention, Detection, and Management. Additional evidence was identified though a query of PubMed and the Cochrane database. Evidence of causality was graded according to the following: A (randomized, controlled clinical trials), B (nonrandomized clinical trials, prospective observational studies, cohort studies, retrospective studies, case-controlled studies, and/or postmarketing surveillance studies), and C (case reports/case series).

RESULTS

A total of 194 systemically administered medications associated with ototoxicity were identified, most commonly antimicrobials (53), psychotropics (21), antihypertensive/antiarrhythmics (19), nonsteroidal antiinflammatory drugs (18), and antineoplastics (16). There was evidence of cochleotoxicity in 165 medications (evidence grading A [22], B [77], C [69]), vestibulotoxicity in 100 medications (evidence grading A [23], B [47], and C [30]), and dizziness in 142 medications (evidence grading A [50], B [76], and C [16]). In addition, a review of the evidence of ototoxicity in ototopical medications is also reviewed.

CONCLUSION

The effect and severity of ototoxicity can vary immensely depending on pharmacological and individual patient risk factors. The intent of this comprehensive review was to help health care providers of all sectors obtain a deeper knowledge of drug-induced ototoxicity to make more informed management decisions for their patients.

Serum Per- and Polyfluoroalkyl Substances Are Associated with Increased Hearing Impairment: A Re-Analysis of the National Health and Nutrition Examination Survey Data

Although studies have shown that per- and polyfluoroalkyl substances (PFAS) are potential environmental ototoxicants, epidemiologic study has been limited. I conducted a cross-sectional study to re-examine the associations between PFAS and hearing impairment. Data were obtained from the National Health and Nutrition Examination Survey (NHANES) 1999–2000, 2003-06, 2009-12, and 2015-16. Perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS), and perfluorononanoic acid (PFNA) were measured in serum samples. Participants were divided into quartiles for each PFAS. Air conduction pure-tone audiometry was administered. Hearing impairment (1: yes, 0: no) was defined as a hearing threshold of more than 25 dB at 500, 1000, 2000, 4000, and 8000 Hz in the worse ear. I assessed the relation of serum PFAS with hearing impairment by the generalized linear mixed model with a logit link and binary distribution. Tests for linear trend across quartiles of serum PFAS were conducted using the median serum PFAS in each quartile as a continuous variable. After adjusting for age, sex, body mass index, education, ethnicity group, and family income, I found positive correlations between PFOA and hearing impairment at 2000 Hz (p-trend < 0.01) and 3000 Hz (p-trend = 0.02); between PFOS and hearing impairment at 500 Hz (p-trend < 0.01), 2000 Hz (p-trend < 0.0001) and 3000 Hz (p-trend = 0.02); between PFNA and hearing impairment at 2000 Hz (p-trend = 0.05), 3000 Hz (p-trend < 0.01), 4000 Hz (p-trend = 0.02), and 8000 Hz (p-trend < 0.01); between PFHxS and hearing impairment at 500 Hz (p-trend = 0.04), 1000 Hz (p-trend = 0.03), and 2000 Hz (p-trend < 0.01). However, some of the findings were not significant when only comparing the highest with the lowest quartile of PFASs. In conclusion, several background serum PFASs are positively correlated with hearing impairment in the United States adult population.

What Are the Current Audiological Practices for Ototoxicity Assessment and Management in the South African Healthcare Context?

The study was an initial exploration of the current ototoxicity assessment and management practices by audiologists in South Africa. An exploratory survey research methodology through a cross-sectional research design was adopted where audiologists were recruited from professional associations' databases in South Africa, using specific inclusion criteria. The study made use of an 18-item web-based survey guided by the Health Professions Council of South Africa (HPCSA) (2018) guidelines which were developed from reviewing international guidelines such as the American Speech-Language-Hearing Association (ASHA,1994) and the American Academy of Audiology (AAA, 2009). The study surveyed 31 audiologists from across the country. Data were analyzed through descriptive statistics. Findings implied significant gaps between knowledge and translation of this knowledge into practice. Over two thirds of the participants engage with ototoxicity monitoring and management, but the practices adopted by them do not align with international standards nor with the national HPCSA guidelines on assessment and management of patients on ototoxic medications. Most participants do not conduct baseline assessments, and the frequency of monitoring is irregular and reduced from the recommended; thus influencing ability for early detection and intervention of ototoxicity within this context. Non-standard assessment battery is used for assessment and monitoring, raising questions about the reliability and validity of the data used to make preventive treatment decisions. Lack of collaborative work between audiologists and the rest of the clinical team involved in the treatment of patients on ototoxic medications was found to be an important contributing factor to the less than optimal ototoxicity management practices. Of factors potentially influencing adherence to guidelines, the institution of employment, specifically employment in a tuberculosis hospital, seemed to have a positive influence, possibly due to the focused nature of the audiologists' scope of practice there as well as availability of resources. The level of education appeared to have no influence. Current findings provide contextually relevant evidence on ototoxicity assessment and management within this context. They raise important implications for guidelines adherence and translating knowledge, policies and guidelines into practice, clinical assessment and management protocols followed, appropriate resource allocation per programme, as well as strategic planning for national ototoxicity assessment and management programmes in context. The findings also raise important implications for low- and middle-income countries, in terms of adopting international guidelines without considering context.

Chemicals, noise and occupational hearing health in South Africa: A mapping study

BACKGROUND

Chemical exposure leading to ototoxicity is a fresh challenge for occupational healthcare in South Africa.

OBJECTIVES

The critical question is: 'what is known about occupational ototoxic chemicals with or without noise exposure in South Africa?'

METHOD

This qualitative, mapping study was completed with published (peer-reviewed) and grey literature from 1979-2019. Data was analysed using the Preferred Reporting Items for Systematic reviews and Meta-Analyses: extension for Scoping Reviews and the Nursing and Allied Health Resources Section subcommittee on Mapping the Literature of Nursing and Allied Health (adapted). Numerical analysis of article type was completed, but the primary focus was on capturing patterns/trends using thematic analysis and ideology critique.

RESULTS

The African Journal of Disability, African Journal of Primary Health Care and Family Medicine, South African Medical Journal, The South African Journal of Communication Disorders [SAJCD] and Health SA Gesondheid) were included with the SAJCD containing one relevant item and seventeen other items were analysed. Research focusses on the mining sector (gold) in Gauteng, and ototoxic medication (tuberculosis and/or human immunodeficiency virus) take precedence. In KwaZulu-Natal, the focus is on commerce and industry across formal and informal sectors. There are no governmental policies that refer to chemical ototoxicity. Occupational hearing loss is configured exclusively on the meme that noise exposure is the only toxin.

CONCLUSION

Chemical exposures are only just beginning to be recognised as ototoxic in South Africa. Hearing conservation programmes should always serve the workers' interests and never bow down to the econometric interests of employers.