Ototoxicity of Povidone-Iodine applied to the middle ear cavity of guinea pigs

Does Hypochlorous Acid Cause Ototoxicity? An Experimental Study

AIM

Hypochlorous acid (HOCl) is a weak acid that ionizes in water. It is an effective antiseptic exhibiting low toxicity on living tissues. We aimed to investigate the ototoxic effects of HOCl on an animal model by using electrophysiological and histological methods.

MATERIALS AND METHODS

The study comprised 32 Sprague-Dawley rats, which were separated into four groups: control group (A), saline solution group (B), 70% isopropyl alcohol + 2% chlorhexidine group (C), and HOCl group (D). After recording the auditory brainstem response (ABR) for basal hearing thresholds (8, 16, 24, and 32 kHz), 0.03 ml of the aforementioned materials was injected intratympanically three times every 2 days in groups B, C, and D. ABR measurements were repeated on the 7th and 21st days. All animals were sacrificed, and temporal bones were prepared for examinations of cochlear histology and vascular endothelial growth factor immunohistochemistry.

RESULTS

Basal hearing levels were normal across all frequencies and groups, with no statistical differentiation. On the 7th and 21st days after the ABR test, all other groups demonstrated a significant deterioration in hearing levels compared with group A. When the results from 7th and 21st days were compared within group D, a partial recovery was observed. In histopathology, groups C and D demonstrated moderate and severe cochlear degeneration, along with decreased immunoreactivity in the organ of Corti, stria vascularis, and spiral ligament.

CONCLUSION

This is the first study to evaluate the safety of using HOCl in otology. Although HOCI is less ototoxic than the disinfectant used, it may have a toxic effect on cochlea.Level of Evidence: Animal Research.

[Microbiome of the external auditory canal and preoperative preparation of patients in otosurgery (literature review)]

OBJECTIVE

To analyze the effectiveness of methods of antiseptic and hygienic preoperative preparation of the operating field in otosurgery.

MATERIAL AND METHODS

A review and an expert assessment of the corresponding research objectives of scientific publications contained in the PubMed and Google Scholar databases have been carried out.

RESULTS

Various studies indicate a lower ototoxicity of 5-10% of the drug povidone-iodine compared to others. Drugs, such as Miramistin, Okomistin, Dioxidine, are actively used in otiatrics in Russia, but no data on their ototoxicity have been noted. The collected data point to the relevance and prospects of studying the microbiome of the external auditory canal, assessing its effect on the course of the postoperative period, depending on various methods of preparation (antiseptic, removal of earwax and hair depilation) of the surgical field for otosurgery.

The safety of povidone-iodine solution in tympanoplasty: a randomised, triple-blind, placebo-controlled study

Objective

Nowadays, povidone-iodine is commonly used as a disinfectant in head and neck procedures. The present study investigated the effect of povidone-iodine, which is used as a disinfectant solution in tympanoplasty, on patients’ hearing.

Methods

A povidone-iodine solution was used as disinfection in chronic otitis media patients undergoing tympanoplasty. In the intervention group, 5% povidone-iodine, was applied to the external auditory canal and remained there for 10 minutes. In the control group, povidone-iodine was used but not allowed to enter the external auditory canal by inserting cotton wool into the canal. To evaluate the adverse effect of povidone-iodine on hearing, the bone conduction level was compared between groups at baseline and one month after exposure.

Results

Bone conduction levels at frequencies 500 Hz, 1 kHz, 2 kHz, 3 kHz, 4 kHz and 8 kHz and mean of bone conduction level in 500 Hz, 1 kHz and 2 kHz were measured and compared respectively between intervention and control group. No significant difference was seen between bone conduction levels of above frequencies and mean frequencies before and one month after surgery. (P-value = 0.321, 0.432, 0.219, 0.489, 0.61, 0.112, 0.324 respectively)

Conclusions

According to the present study, currently available 5% povidone-iodine did not affect hearing and therefore, can be comfortably used for preparation and disinfection in otologic surgeries.

Prevention of Chlorhexidine Ototoxicity With Poloxamer in Rats

OBJECTIVE

Skin preparations, like chlorhexidine, are toxic to the inner ear, preventing their use as a preoperative skin disinfectant in the presence of a nonintact eardrum (e.g., perforation or tube). We aimed to determine if a poloxamer gel applied over perforated eardrums could prevent chlorhexidine ototoxicity.

STUDY DESIGN

Controlled, in vivo.

SETTING

Academic research laboratory.

SUBJECTS AND METHODS

Bilateral myringotomies were performed on 20 Sprague-Dawley rats. Half had poloxamer placed over both eardrums before treatment. All rats had chlorhexidine instilled in one ear and saline in the other. Auditory brainstem response thresholds were measured before and 2- and 4-weeks posttreatment. Cochlear hair cell damage was assessed using scanning electron microscopy.

RESULTS

Ears with chlorhexidine without poloxamer had significant hearing loss, 37 to 50 dB worse than the other three ear treatments at 2 and 4 weeks posttreatment, at all tested frequencies (4, 18, 16, and 24 kHz; all p < 0.0001). No significant hearing loss was observed in ears that were treated with poloxamer and chlorhexidine (-2 to 8 dB) and the results were not different from the ears that received saline, with or without poloxamer (-2.5 to 8 dB and 5-17 dB; p > 0.05). Electron microscopy showed far more outer hair cell damage in the no poloxamer + chlorhexidine ears compared with the other three treatments.

CONCLUSION

The use of a poloxamer barrier may be an effective approach to prevent ototoxicity before chlorhexidine disinfection of the ear with a nonintact tympanic membrane.

Ototoxicity of povidone-iodine - A case report

Objective

The ototoxicity of povidone-iodine has been documented in animal studies. However, there is limited evidence of these ototoxic effects in humans. This is the first report to show the ototoxic effects of povidone-iodine in a human subject.

Patient

A 36-year-old woman came to our hospital complaining of left unilateral persistent hearing loss. One month before presentation, her child had accidentally struck her on her left ear. She applied approximately three drops of povidone-iodine (10% weight/volume) into her left auditory canal. Immediately after application, she felt severe pain and vertigo. An audiogram revealed severe left unilateral sensorineural hearing loss. Magnetic resonance imaging showed mild enhancement of the left vestibule and basal turn of the left cochlea.

Conclusions

Even a single application of povidone-iodine could cause significant hearing loss and disequilibrium. It should, therefore, be used with caution.

Systematic review of ototoxic pre-surgical antiseptic preparations - what is the evidence?

Objective

There is uncertainty regarding the safety of surgical antiseptic preparations in the ear. A systematic review of the literature was conducted to assess the evidence regarding ototoxicity of surgical antiseptic preparations.

Methods

A literature search was conducted using the PRISMA methods. Key words included “ototoxicity” “hearing loss”, “antiseptic”, “surgical preparation”, “tympanoplasty”, “vestibular dysfunction”, “chlorhexidine”, “iodine”, “povidone”, “ethanol”, and “hydrogen peroxide” using Medline, Embase, Cochrane Library, Scopus and Web of Science. We included peer-reviewed papers that 1) objectively measured ototoxicity in humans or animals through hearing, vestibular function or histologic examination, 2) studied topically applied surgical antiseptic preparations, 3) were either in English or had an English abstract. We excluded papers that were 1) in vitro studies, 2) ear trauma studies, 3) studies of ototoxic ear drops intended for therapy, or 4) case reports. Studies included in the final review were screened using the PRISMA method.

Current systematic review registration number pending: 83,675.

Results

Fifty-six papers were identified as using PRISMA criteria. After applying our exclusion criteria, 13 papers met overall study criteria. Of these, six papers reported ototoxicity of iodine based solutions, five papers reported ototoxicity of chlorhexidine and ethanol and two papers assessed hydrogen peroxide. All papers reviewed were animal studies. Iodine based solutions show least harm overall, while chlorhexidine and high concentrations of alcohol based solutions showed most harm. The evidence on hydrogen based solutions was inconclusive.

Conclusions

The overall evidence for anyone antiseptic solution is weak. There is some evidence that iodine, chlorhexidine, hydrogen peroxide and alcohol based antiseptics have ototoxicity. Conclusive evidence for human ototoxicity from any solution is not strong.

Lugol's solution eradicates Staphylococcus aureus biofilm in vitro

OBJECTIVES

The aim of the study was to evaluate the antibacterial efficacy of Lugol's solution, acetic acid, and boric acid against Staphylococcus aureus biofilm.

METHODS

The efficacy of Lugol's solution 1%, 0.1%, and 0.05%, acetic acid 5% or boric acid 4.7% for treatment of Staphylococcus aureus biofilm in vitro was tested using 30 clinical strains. Susceptibility in the planktonic state was assessed by disk diffusion test. Antiseptic effect on bacteria in biofilm was evaluated by using a Biofilm-oriented antiseptic test (BOAT) based on metabolic activity, a biofilm bactericidal test based on culturing of surviving bacteria and confocal laser scanning microscopy combined with LIVE/DEAD staining.

RESULTS

In the planktonic state, all tested S. aureus strains were susceptible to Lugol's solution and acetic acid, while 27 out of 30 tested strains were susceptible to boric acid. In biofilm the metabolic activity was significantly reduced following exposure to Lugol's solution and 5% acetic acid, while boric acid exposure led to no significant changes in metabolic activities. In biofilm, biocidal activity was observed for Lugol's solution 1% (30/30), 0.1% (30/30), and 0.05% (26/30). Acetic acid and boric acid showed no bactericidal activity in this test. Confocal laser scanning microscopy, assessed in 4/30 strains, revealed significantly fewer viable biofilm bacteria with Lugol's solution (1% p < 0.001, 0.1% p = 0.001 or 0.05% p = 0.001), acetic acid 5% for 10 min (p = 0.001) or 30 min (p = 0.015), but not for acetic acid for 1 min or boric acid.

CONCLUSION

Lugol's solution 1.0% and 0.1% effectively eradicated S. aureus in biofilm and could be an alternative to conventional topical antibiotics where S. aureus biofilm is suspected such as external otitis, pharyngitis and wounds.

OTO-201: nonclinical assessment of a sustained-release ciprofloxacin hydrogel for the treatment of otitis media

HYPOTHESIS

OTO-201 can provide sustained release to the middle ear and effectively treat otitis media, when compared with FDA-approved ciprofloxacin otic drop formulations.

BACKGROUND

There is an unmet medical need for antibiotic therapy that can provide a full course of treatment from a single administration by an otolaryngologist at the time of tympanostomy tube placement, obviating the need for twice daily multiday treatment with short-acting otic drops.

METHODS

Studies in guinea pigs and chinchillas were conducted. OTO-201 was administered as a single intratympanic injection and compared with the twice daily multi-day treatment with Ciprodex or Cetraxal otic drops.

RESULTS

OTO-201 demonstrated sustained release of ciprofloxacin in the middle ear compartment for days to approximately 2 weeks depending on the dose. The substantial C(max) values and steady drug exposure yielded by OTO-201 were in contrast to the pulsatile short lasting exposure seen with Ciprodex and Cetraxal. OTO-201 was also effective in a preclinical chinchilla model of Streptococcus pneumoniae-induced otitis media. The degree of cure was comparable to that afforded by Ciprodex and Cetraxal. There was no evidence of middle or inner ear pathology in guinea pigs treated with OTO-201, unlike Ciprodex and Cetraxal, which both demonstrated mild cochlear ototoxicity. No adverse effects of the poloxamer 407 vehicle were noted.

CONCLUSION

Intratympanic injection of OTO-201 constitutes an attractive treatment option to twice daily multiday dosing with ciprofloxacin ear drops for the treatment of otitis media, as evidenced by superior middle ear drug exposure, efficacy in an acute otitis media model, safety of administration, and convenience of a single dose regimen.

Ototoxicity of gentian violet on the guinea pig cochlea

PURPOSE

Gentian violet (GV) is an antimicrobial and antifungal agent that has been used widely to treat intractable discharge in the ear. The purpose of this report is to warn clinicians about the ototoxic effect of GV in the middle ear.

MATERIALS AND METHODS

GV ototoxicity was evaluated by measuring compound action potentials (CAPs) in the VIIIth nerve in adult Hartley guinea pigs. The middle ear cavities of the animals were filled with GV solution (0.5% or 0.13%), and CAPs were measured after intervals of 5 and 30 minutes and 1, 2, 6, and 24 hours. After all measurements were completed, the temporal bones were harvested for histopathologic evaluation. Celloidin-embedded specimens were cut into 20-μm slices and examined using light microscopy. The bacteriostatic activity of GV was evaluated using a disk-diffusion assay.

RESULTS

A 0.5% GV solution produced a mild elevation in the CAP threshold at 30 minutes, a greater reduction at 1 hour, and complete abolishment of CAP at 24 hours. A 0.13% GV solution caused mild elevation in the CAP threshold at 2 hours and severe elevation at 6 hours. Massive new bone formation was found in the middle ear cavity at 6 weeks. GV concentrations of 0.13% and 0.06% were effective against all bacteria tested, with the exception of Pseudomonas aeruginosa.

CONCLUSIONS

Although GV has marked antibacterial and antifungal activities, its use should be limited to the external ear canal. GV exerts an ototoxic effect in a concentration- and time-dependent manner, and so the use of this drug in the middle ear cavity is not recommended.

Ototoxicity of different concentrations povidone-iodine solution applied to the middle ear cavity of rats

To investigate the ototoxic effects of different concentrations of povidone-iodine solutions applied to the middle ear cavity of rats using distortion product otoacoustic emissions. 24 healthy 3-3.5-month-old adult female Sprague-Dawley rats were randomly divided into three groups. The group A (n = 8 ears) received 5 % povidone-iodine solution to the right ear, the group B (n = 8 ears) received 7.5 % povidone-iodine solution to the right ear and the group C (n = 8 ears) received 10 % povidone-iodine solution to the right ear. All animals received saline solution to the left ear as a control (n = 24 ears). The animals were tested before, 1 and 10 days after solutions administration to the middle ear. The resulting distortion product otoacoustic emissions were evaluated at 1.5, 2, 3, 4, 5, 6, 7, 8, 10 and 12 kHz. Statistically significant reductions in DP-gram amplitudes were noted at high frequencies (7, 8, 10, 12 kHz) in the group A at day 1 but this effect return at day 10. In group B and group C statistically significant differences were recorded for low and high frequencies (1.5, 2, 7, 8, 10, 12 kHz) according to the control group at day 1 and 10. 7.5 and 10 % povidone-iodine showed a significant ototoxic effect on day 1 and 10. But this toxic effect could not be elicited in 5 % povidone-iodine group on day 10. The present study revealed that commercially available high concentration povidone-iodine solution may cause significant ototoxic effects when applied topically through a perforated ear drum in rats. Based on results of this experiment, high concentration povidone-iodine solutions should not be used for preoperative surgical site cleansing for otologic surgery.

Povidone-iodine-induced cell death in cultured human epithelial HeLa cells and rat oral mucosal tissue

Although povidone-iodine (PVP-I) has been used as a gargle since 1956, its effectiveness and material safety have been remained controversial. The aim of this study was to investigate the toxicity of PVP-I to epithelial cells in a concentration range significantly lower than that used clinically. Study design was in vitro laboratory investigations and in vivo histological and immunologic analysis. We examined the effects of PVP-I at concentrations of 1 × 10(-2) to 1 × 10(3) μM and 1 × 10(-4) to 1 × 10 μM on HeLa cells as a model of epithelial cells and rat oral mucosa, respectively, after 1 or 2 days of exposure. Annexin V/FLUOS was used to distinguish live, apoptotic and necrotic cells. The terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) method was also used to observe whether apoptotic epithelial cells exist in rat oral mucosa after 1 day of exposure of PVP-I. HeLa cells developed concentration-dependent cytotoxicity, and epithelium of rat oral mucosa was thinned in a concentration-dependent manner. HeLa cell apoptosis increased after 1 × 10(0) μM of PVP-I exposure for 2 days. In the TUNEL method, many apoptotic epithelial cells were observed in the rat oral mucosa after 1 day of exposure to diluted 1 × 10(-2) μM of PVP-I, but minimal apoptotic epithelial cells were observed using 1 × 10(-3) μM of PVP-I. Our findings suggest that exposure to PVP-I, of which concentrations are even lower than those used clinically, causes toxicity in epithelial cells. This knowledge would help us better understand the risk of the use of PVP-I against mucosa.

Systematic review of animal models of middle ear surgery

Animal models of middle ear surgery help us to explore disease processes and intervention outcomes in a manner not possible in patients. This review begins with an overview of animal models of middle ear surgery which outlines the advantages and limitations of such models. Procedures of interest include myringoplasty/tympanoplasty, mastoidectomy, ossiculoplasty, stapedectomy, and active middle ear implants. The most important issue is how well the model reflects the human response to surgery. Primates are most similar to humans with respect to anatomy; however, such studies are uncommon now due to expense and ethical issues. Conversely, small animals are easily obtained and housed, but experimental findings may not accurately represent what happens in humans. We then present a systematic review of animal models of middle ear surgery. Particular attention is paid to any distinctive anatomical features of the middle ear, the method of accessing the middle ear and the chosen outcomes. These outcomes are classified as either physiological in live animals, (e.g., behavioural or electrophysiological responses), or anatomical in cadaveric animals, (e.g., light or electron microscopy). Evoked physiological measures are limited by the disruption of the evoking air-conducted sound across the manipulated middle ear. The eleven identified species suitable as animal models are mouse, rat, gerbil, chinchilla, guinea pig, rabbit, cat, dog, sheep, pig and primate. Advantages and disadvantages of each species as a middle ear surgical model are outlined, and a suggested framework to aid in choosing a particular model is presented.

Ototopic applications of povidone iodine/dexamethasone in the rat

HYPOTHESIS

Repeated applications of low-concentration povidone iodine (PI) combined with dexamethasone (Dex) through a tympanic membrane ventilation tube will not cause ototoxic changes in the rat.

BACKGROUND

Otitis externa (OE) and acute otitis media (AOM) are 2 of the most common otologic disorders requiring outpatient antibiotic treatment. The development of topical treatments that are easy to administer would help to limit systemic exposure to antibiotics in these patients. Topical formulations containing Dex and low-dose PI were designed to provide both antimicrobial and anti-inflammatory effects for the treatment of OE and AOM. Treatment with PI alone has shown mixed results in studies designed to determine PI. Low concentrations of PI combined with Dex should yield less ototoxicity while maintaining effectiveness.

METHODS

We performed tympanostomies on rats, inserting a ventilation tube to administer 1% or 2% PI, plus 0.1% Dex over a period of 7 days. Hearing was accessed via auditory brainstem response (ABR) testing over the duration of the study and histologic analysis was performed 15 days after the initial application to determine the effect of administration of PI/Dex on middle and inner ear structures.

CONCLUSION

The preparations used in the present investigation were formulated to allow repeated applications to both the external and middle ear, without risk to hearing or equilibrium. Neither of the PI/Dex formulations tested caused pathologic changes in the ear that significantly affected equilibrium, hearing function or morphology.

Topical treatment of chronic suppurative otitis media

Chronic suppurative otitis media (CSOM) is a chronic inflammation of the middle ear and mastoid cavity presenting with ear discharge or otorrhea through a non-intact tympanic membrane. CSOM is the most common cause of childhood hearing impairment in developing countries. Accurate diagnosis depends on a high index of suspicion, micro-otoscopic examination, and judicious use of imaging as required. CSOM can be classified into 3 types: tubotympanic, atticoantral, and post-tympanostomy tube insertion. Aerobes, anaerobes and fungi are all potential pathogens in CSOM. This review summarizes the results of recent studies on the bacteriology of CSOM, biofilms, and the role of the nasopharynx pathogens that may have important implications for the treatment of this important pathology; that is often associated with misdiagnosis or delayed diagnosis. Particular emphasis will be placed on topical treatment options including choices of antibiotic, antifungal, and antiseptic agents, delivery technique, spectrum of activity, and risk of ototoxicity.