Effect of melatonin on otoprotection in rodents: a systematic review with meta-analysis

OBJECTIVES

To determinate the otoprotective efficacy of melatonin.in experimental models of rodents through a systematic review of the literature.

METHODS

Altogether, 154 articles were found in four databases. The PICOS strategy (Population, Intervention, Comparison, and Outcome) was used to define the eligibility criteria. Studies that met the inclusion criteria for the second step were included in a qualitative synthesis. Each study type was analyzed with the CAMARADES quality of assessment's checklist and the SYRCLE RoBS risk of bias.

RESULTS

Seven articles were selected, and four were included in the meta-analysis. It was possible to obtain seven outcomes according to the standard auditory frequencies presented among the studies, considering a minimum of three standard frequencies. The outcomes analyzed were for the frequencies of 1500, 2000, 3000, 4000, 5000, 6000, and 8000 Hz.

CONCLUSION

Melatonin can provide protection against the ototoxic effects of cisplatin and aminoglycosides at 5000 Hz, 6000 Hz, and 8000 Hz, thereby minimizing the reduction in Otoacustic Emissions (OAE) amplitude. The same effect was not observed in the lower frequencies. Despite the limited number of studies that were evaluated, the results appeared consistent in higher frequencies. However, the methodology of the available studies did not meet the necessary methodological rigor that promotes the safe replicability of these studies.

Oral Administration of TrkB Agonist, 7, 8-Dihydroxyflavone Regenerates Hair Cells and Restores Function after Gentamicin-Induced Vestibular Injury in Guinea Pig

The causes of vestibular dysfunction include the loss of hair cells (HCs), synapses beneath the HCs, and nerve fibers. 7, 8-dihydroxyflavone (DHF) mimics the physiological functions of brain-derived neurotrophic factor. We investigated the effects of the orally-administered DHF in the guinea pig crista ampullaris after gentamicin (GM)-induced injury. Twenty animals treated with GM received daily administration of DHF or saline for 14 or 28 days (DHF (+) or DHF (-) group; N = 5, each). At 14 days after GM treatment, almost all of the HCs had disappeared in both groups. At 28 days, the HCs number in DHF (+) and DHF (-) groups was 74% and 49%, respectively, compared to GM-untreated control. In the ampullary nerves, neurofilament 200 positive rate in the DHF (+) group was 91% at 28 days, which was significantly higher than 42% in DHF (-). On day 28, the synaptic connections observed between C-terminal-binding protein 2-positive and postsynaptic density protein-95-positive puncta were restored, and caloric response was significantly improved in DHF (+) group (canal paresis: 57.4% in DHF (+) and 100% in DHF (-)). Taken together, the oral administration of DHF may be a novel therapeutic approach for treating vestibular dysfunction in humans.

A scoping review of global aminoglycoside antibiotic overuse: A potential opportunity for primary ototoxicity prevention

BACKGROUND

Aminoglycosides are widely used, broad-spectrum antibiotics with significant potential for ototoxicity. Global efforts to prevent ototoxicity must account for aminoglycoside overuse and non-prescription use.

OBJECTIVES

The goals of this study were to a) estimate the prevalence of aminoglycoside overuse by synthesizing evidence on self-medication, over the counter (OTC) availability, and household antibiotic storage for later use, and to report the specific aminoglycosides used and the predictors of overuse, and b) leverage this information to comment on potential risk of ototoxicity.

METHODS

Two systematic search strings were conducted to extract peer-reviewed articles published from 2005 to 2020. The first focused on overuse of aminoglycoside antibiotics. The second focused on potentially ototoxic effects of aminoglycosides related to drug overuse.

RESULTS

A total of 26 articles were included (first search string: n = 21; second search string: n = 5). The prevalence of aminoglycoside self-medication was high and household storage and OTC availability of aminoglycosides was common. Gentamicin was the most commonly overused aminoglycoside. No studies provided information on antibiotic dosing or resultant toxicities, including ototoxicity.

CONCLUSIONS

The limited available evidence indicates that antibiotic overuse (self-medication, home storage, and non-prescription availability) is relatively common, especially in low resource settings, and that aminoglycoside antibiotics comprise a variable, but concerning, proportion of non-prescribed antibiotics. Additional evidence is needed to evaluate the relationship between these dispensing patterns and ototoxicity.

A validation study of auditory function in an aminoglycoside-furosemide ototoxicity mouse model: Auditory brainstem response and distortion product otoacoustic emissions

Sensorineural hearing loss due to ototoxic drugs remains as a conflict as the treatment option with aminoglycosides. Ototoxic mouse model was produced with the administration of ototoxic drugs aminoglycoside kanamycin and loop-diuretic furosemide, thus validation of auditory function of the mouse model is needed to determine the efficacy of the drugs. Kanamycin sulfate 550 mg/kg (VWR life sciences, PA, USA) and furosemide 130 mg/kg (Lasix, Handok, Korea) were administered through subcutaneous and intraperitoneal injection respectively. Auditory brainstem response and distortion otoacoustic emission tests were performed on days 3,5,7,10,14 post administration of the ototoxic drug. Thresholds in response to the stimulus given in the auditory brainstem recordings and distortion otoacoustic emission tests were obtained. The hearing threshold shift to high stimulus intensity was observed post administration of the ototoxic drug. Latency of the ABR peak waves were recorded and analyzed, latency delay was observed as hearing threshold increases. These findings will further support in the application of this animal model in various studies regarding ototoxic hearing loss.

Bilateral Vestibular Weakness

Bilateral vestibular weakness (BVW) is a rare cause of imbalance. Patients with BVW complain of oscillopsia. In approximately half of the patients with BVW, the cause remains undetermined; in the remainder, the most common etiology by far is gentamicin ototoxicity, followed by much rarer entities such as autoimmune inner ear disease, meningitis, bilateral Ménière’s disease, bilateral vestibular neuritis, and bilateral vestibular schwannomas. While a number of bedside tests may raise the suspicion of BVW, the diagnosis should be confirmed by rotatory chair testing. Treatment of BVW is largely supportive. Medications with the unintended effect of vestibular suppression should be avoided.

Otic drug delivery systems: formulation principles and recent developments

Disorders of the ear severely impact the quality of life of millions of people, but the treatment of these disorders is an ongoing, but often overlooked challenge particularly in terms of formulation design and product development. The prevalence of ear disorders has spurred significant efforts to develop new therapeutic agents, but perhaps less innovation has been applied to new drug delivery systems to improve the efficacy of ear disease treatments. This review provides a brief overview of physiology, major diseases, and current therapies used via the otic route of administration. The primary focuses are on the various administration routes and their formulation principles. The article also presents recent advances in otic drug deliveries as well as potential limitations. Otic drug delivery technology will likely evolve in the next decade and more efficient or specific treatments for ear disease will arise from the development of less invasive drug delivery methods, safe and highly controlled drug delivery systems, and biotechnology targeting therapies.

Topical otic antibiotics: clinical cochlear ototoxicity and cost consideration

OBJECTIVE

Determine the incidence of clinical cochlear ototoxicity in routine use of Cortisporin after ventilation tube placement. Cost differential between use of Cortisporin and fluoroquinolone agents was evaluated.

METHODS

A retrospective review of 500 patients was performed. Cortisporin otic suspension was used for 5 days following ventilation tube insertion.

RESULTS

Testing following surgery indicated a sensorineural hearing loss (SNHL) in 19 (2.1%) ears. The SNHL existed prior to the surgery and there was no deterioration in the hearing postoperatively. The total cost for our study group who used Cortisporin was $15,500. If Floxin had been prescribed the cost would have been $45,000. Had Ciprodex been prescribed, the cost would have been $49,500.

CONCLUSION

Our study demonstrates no clinical cochlear ototoxicity in children who received Cortisporin following ventilation tube placement. The cost differential for prescribing fluoroquinolone drops is significant.

EBM RATING

C-4.

Topical antibiotic ear drops: are they safe?

A discharging ear is a very common condition for the general practitioner and the ENT surgeon. Oral and intravenous antibiotics have potential complications, are costly, and exhibit increasing resistance. This study explores the advantages and disadvantages of all common otic preparations and compares effectiveness, safety, cost and complication rates. In chronic otitis media (chronic discharging ears), topical antibiotics seem to be the treatment of choice by comparison with oral or intravenous antibiotics. Cultures and antibiograms do not correspond directly to clinical efficacy, as laboratory determination of resistance does not take into account the high concentration of antibiotics in local preparations. It is safer to use quinolone drops as a first-line treatment, but it is still possible to use short courses of other drops if quinolones are either unavailable or contraindicated (e.g. allergy), or when bacteria are resistant to them. However, in such a situation, a round window membrane involved in an established inflammatory process and therefore less permeable to the passage of topical preparations is the preferred setting, as ototoxicity is a potential complication, especially in the case of gentamicin, in which case patients should be warned accordingly.