Ear Preparation Research Articles

Effective pharmaceutical management of Acute Otitis Externa: guidance and prescribing considerations

Acute Otitis Externa is a common condition observed by physicians, particularly in primary care. The condition usually occurs due to bacterial infection, so antibiotic therapy is frequently indicated. Oral antibiotics are rarely necessary but are still being prescribed, despite a wide range of available topical preparations. Choosing a topical preparation can sometimes be challenging for prescribers, however, consideration of a range of different factors is necessary. This article provides a review of the currently recommended prescribing practice and outlines key topical antibiotic ear preparations available in the UK for treatment of Acute Otitis Externa. As no one topical ear preparation is more effective than another, a consideration of the benefits and risks of each treatment is needed to enable therapeutic resolution of Acute Otitis Externa. Furthermore, patient compliance should be adequately considered to increase the likelihood of patient adherence to treatment.

Therapeutic Efficacy of Different Ear Cleanser in Management of Canine Otitis

The objective of this study was to compare the therapeutic efficacy of three different ear cleansers in 30 dogs of various breeds suffering from otitis. Based on history and clinical signs, ear exudates were collected by aseptic cotton swab for isolation and identification of organisms. The cerumen deposition in-ear canal was cleared using one of the ear preparations, viz., ear cleanser-I (0.2 % salicylic acid and 0.3 % phenoxyethanol) ear cleanser - II (chlorhexidine, propylene glycol and tris–EDTA) or ear cleanser-III (2% para-dichlorobenzene, benzocaine 2.7%, chlorbutol 5% and turpentine oil 15 %). Systemic/local antibiotics were used as per sensitivity testing. The treatment protocol found effective in the management of ear infections included cleaning the ear debris using ceruminolytic preparations/ear wax dissolvent, viz, ear drop. Ear cleanser-III showed excellent results (100%) in ceruminous as well as bacterial otitis with subsequent instillation of ear preparations containing antibacterial drug(s) and antifungal agents compared to cleanser-II (90%) and cleanser-I (70%).

A RECENT OVERVIEW OF LOCALLY ADMINISTERED TOPICAL OTIC DOSAGE FORMS

Ear diseases can significantly affect the life quality of patient, so the need for effective treatment encourages the development of new active substances and new dosage forms. Otic dosage forms may be solutions, suspensions, or emulsions of drops or spray for washing the ear or for administration to the ear canal. They may be ear-wash preparations in the form of solution or emulsion, or medicated semi-solid or solid preparations in the form of gel, cream, ointment, powders, sticks or buffers. These preparations can contain one or much more active ingredients in a suitable vehicle and additionally may contain different excipients for isotonisation, pH adjustment, viscosity or solubility enhancement, buffering, preservation, etc. These excipients should not alter the pharmacological effect of active substances and should not be toxic or irritating. Ear preparations can be packaged in single or multiple doses. It is anticipated that otic dosage forms will be improved and the importance of locally applied, safe and highly controlled drug delivery systems will increase in the future.

Imaging of Inflammatory Responses in the Mouse Ear Skin.

The skin is one of the most physiologically important organs where the organism comes into contact with the external environment and is often a site where pathogen entry first occurs. Thus, a better understanding of the specialized cellular behavior of the immune system in the skin may be important for the improved treatment of diseases. Here, we describe in detail a procedure to image the dorsal mouse ear skin, using a customized ear stage and its associated coverslip holder, with an upright multiphoton microscope. As a demonstrative example, we describe the specific protocol for visualizing robust neutrophil trafficking in albino lysozyme-EGFP mice in response to zymosan particles. Instructive sections are provided for the mouse ear preparation, intradermal delivery of zymosan, design and use of the custom ear stage, as well as a solution for the uninterrupted live imaging of mice during prolonged sessions within a dark box. The mouse ear is easily accessible for imaging, and unlike most other organs, does not require any invasive surgery to be performed.

Activity In Vitro of Clotrimazole against Canine Methicillin-Resistant and Susceptible Staphylococcus pseudintermedius.

Emergence of multidrug-resistance in Staphylococcus pseudintermedius (SP) has increased interest in topical therapy as an alternative to systemic antibiotics in canine pyoderma. The antifungal imidazole, clotrimazole, is contained in numerous licensed canine ear preparations. Its in vitro activity against SP has not been evaluated, although previous studies have shown that the related imidazole, miconazole, has significant anti-staphylococcal efficacy. We therefore determined minimum inhibitory concentrations (MICs) of clotrimazole amongst 50 SP isolates (25 methicillin-resistant [MR]SP and susceptible [MS]SP) collected from dogs in Germany during 2010–2011 using an agar dilution method (CLSI VET01-A4). MICs amongst MRSP and MSSP were comparable (MIC50 and MIC90 = 1mg/L for both groups, p = 0.317); overall, 49 isolates had MIC = 1 mg/L and one had MIC = 0.5 mg/L. The relatively low MICs obtained in this study are likely to be exceeded by topical therapy and thus further clinical evaluation of clotrimazole use in canine superficial pyoderma and otitis externa caused by MRSP and MSSP is now warranted.

Successful management of otitis externa

Otitis is one the most common problems seen in dogs. Most acute cases can be managed with topical polyvalent ear preparations. However, these cases frequently evolve into chronic or recurrent...

Comparative study of RP-HPLC versus TLC-spectrodensitometric methods applied for binary mixtures of fluoroquinolones and corticosteroids

Summary Reversed phase high-performance liquid chromatography (RP-HPLC) and thin-layer chromatography (TLC)-spectrodensitometric methods have been developed and validated for the separation and quantitation of two binary mixtures: Ofloxacin (OFX) and dexamethasone (DXM) in eye preparation; ciprofloxacin hydrochloride (CIP) and hydrocortisone (HYD) in ear preparation. The linearity ranges of RP-HPLC methods were found to be (2.5–45 μg mL−1) for OFX, (2.5–50 μg mL−1) for DXM and (1–8 μg mL−1) for both CIP and HYD. The percentage recoveries/relative standard deviation (RSD) were found to be 100.36/1.38, 100.13/1.49, 99.98/0.61 and 100.28/1.27, respectively. The linearity ranges of TLC-spectrodensitometric methods were found to be (0.5–2 μg band−1), (0.5–3.5 μg band−1), (0.2–1.6 μg band−1), and (0.6–2 μg band−1) for OFX, DXM, CIP, and HYD, respectively. The percentage recoveries/RSD were found to be 99.98/1.06, 99.93/1.18, 99.74/1.27, and 99.94/1.54, respectively. A comparative study was conducted to show the advantages of the proposed methods which showed that the TLC-spectrodensitometric methods were simpler, more sensitive, and economic, while RP-HPLC methods were more precise and robust. The methods were validated in compliance with the ICH guidelines and were successfully applied for determination of the selected drugs in their laboratory-prepared mixtures and commercial dosage forms.

The action of isoprenaline on the perfused vessels of the rabbit ear.

Abstract In rabbit isolated perfused ear preparations isoprenaline in doses of 1 to 5 μg caused a vasodilatation which was specifically blocked by propranolol. In a minority of experiments larger doses of isoprenaline (5 to 10 μg) caused vasoconstriction. The vasodilatations to isoprenaline were increased by raising vascular tone with barium chloride whereas ergotamine and sympathetic stimulation were relatively ineffective. In the isolated ear central artery preparation, isoprenaline caused a vasoconstriction due to α-receptor stimulation. A vasodilator response due to β-receptor stimulation was revealed when perfusion pressure was raised with barium chloride. It is concluded that α- and β-adrenergic receptors are present in both preparations but a higher proportion of β-receptors are present in the whole ear.

Development of spontaneous activity and response properties of primary lagenar neurons in the chick.

Here, we report for the first time developmental changes in spontaneous activity and in response properties of single nerve fibers from the macular chick lagena. Such aspects are important in order to get insight into the functional role of the lagena which remains undetermined. For this purpose, we used intracellular and extracellular single-unit recording techniques in an isolated inner ear preparation from the chicken at ages E15 and P1. At E15, afferent fibers displayed a low irregular spontaneous discharge rate (41 +/- 14 spikes/s, CV = 1.17 +/- 0.1), which was replaced by regular high frequency spontaneous activity at P1 (CV = 0.48 +/- 0.8, 89 +/- 27 spikes/s). During the developmental period including E15, the percentage of silent neurons was 60% while that of P1 was 40%. The synaptic activity was higher at E15 than at P1. The action potential waveform generated at E15 had small amplitude and derivative depolarization, and consequently, a large duration in correlation with respect to action potential waveform at P1 (respectively: 53 +/- 2 vs. 65 +/- 3 mV, 60 +/- 11 vs. 109 +/- 20 mV/ms, 3.6 +/- 0.4 vs. 1.1 +/- 0.12 ms). In addition, we recognized two response dynamics to the injection of current steps: phasic, or rapidly adapting neurons and tonic, or slowly adapting neurons. Our results indicate similar developmental processes for the lagena as described for the vestibular system in other species, in agreement with the known morphological characteristics of this otholitic end organ. The presence of more than one subtype of afferent neuron also correlates with previous reports on vestibular afferents with analogous electrophysiological properties, strongly suggesting the vestibular nature of the lagena.

Sound Transduction in the Mammalian Outer Hair Cells: Prestin Activity is Required for Proper Deflection of the Stereocilia Bundle

The outer hair cell (OHC) body is capable of prestin-driven electromotility leading to force generation that increases the vibration of the hearing organ critical for auditory sensitivity. At the cell's apex, the stereocilia bundle deflects as a unit during sound stimulation (Fridberger et al, 2006). Such a deflection converts nanometric displacements into electrical signals transmitted to the auditory nerve. Very little is however known about how sound stimuli cause the bundle to deflect, especially, the possible contribution of prestin-induced cell body vibrations to this deflection has never been investigated. Here we investigated the influence of the membrane protein prestin activity on the bundle deflection, in an intact ear preparation from the Guinea pig. Prestin was previously shown to be specifically inactivated by salicylate and tributyltin. Using an approach combining rapid confocal imaging and optical flow-based computation, the bundle deflection was studied under simultaneous sound stimulus administered at 50-350HZ, a frequency band typical of OHCs vibrations in the apex of the cochlea. To our surprise and irrespective of the prestin inhibitor used, sound-induced bundle deflection drastically increases, specifically, near the best frequency whose position was altered. Likewise, the vibration of the bundle tip intensified. Moreover, the shape of the bundle deflection's pattern was affected. Our data challenge the general assumption that prestin inactivation decreases the vibrations of the cochlear's structures. Because no consistent change was observed for vibrations of the reticular lamina, the increase in the bundle deflection may be caused by a robust vibration of the top. The data suggest that prestin motor's activity regulates the tuning of the bundle vibrations and may explain how the stereociliary and saumatic amplifiers interact during sound transduction in the mammalian ear.

Vestibular primary afferent activity in an in vitro preparation of the mouse inner ear

Most information on the properties of mammalian vestibular primary afferents has been obtained in deeply anesthetized animals, in vivo. Generally, non-human primates and larger rodents have been the species of choice. Investigations using smaller rodents, such as the laboratory mouse, have been limited despite the increasing availability of naturally occurring or engineered mutants that result in balance disorders. Furthermore, in vitro preparations of the intact peripheral vestibular apparatus are only available for non-mammalian vertebrates. To take advantage of the genetic/molecular advances available in mice and the utility of in vitro preparations that permit manipulations of the extracellular milieu, we developed an isolated mouse inner ear preparation with the attached eighth cranial nerve for electrophysiological recording. Intra-axonal recordings of background activity in vestibular primary afferents were obtained in a modified Ringer's solution (0.25 mM Ca 2+; 3.25 mM Mg 2+) at 22 °C. We also recorded afferent activity in the presence of neuroactive drugs known to affect various stages of the transduction cascade. These results, together with responses to sinusoidal mechanical deformation of the membranous ducts, showed that transduction mechanisms remain viable. Where possible, we also obtained results in vivo for comparison. In future, the in vitro mouse preparation will allow investigation of the effects of genetic manipulations and pharmacological agents on the intact peripheral vestibular apparatus.

Antibodies against inner ear proteins in the sera of patients with inner ear diseases

Sera from patients with various inner ear diseases, especially Meniere's disease, were investigated by Western blot against guinea pig inner ear preparations. Of 45 patients, 24 (53%) with various inner ear diseases had antibodies against inner ear proteins, compared with none of 10 (0%) in control subjects without inner ear diseases. Of the 10 proteins that showed a positive reaction with patient sera, the 28-kD band was unique in that it appeared only in the membranous fraction of the inner ear and was highly positive (28%) in reaction with Meniere's disease patient sera. The results in the present study with proteins extracted from guinea pig inner ears were consistent with our previous study with proteins from human inner ear. It suggests that the 28-kD protein may be a candidate for detecting autoimmune inner ear disease (AIED).

Gap Junction-Dependent Increases in Smooth Muscle cAMP Underpin the EDHF Phenomenon in Rabbit Arteries

We have investigated the role of cAMP in nitric oxide (NO)- and prostanoid-independent vascular relaxations evoked by acetylcholine (ACh) in isolated arteries and perfused ear preparations from the rabbit. These EDHF-type responses are shown to be associated with elevated cAMP levels specifically in smooth muscle and are attenuated by blocking adenylyl cyclase or protein kinase A (PKA). Relaxations are amplified by 3-isobutyl-1-methylxanthine, which prevents cAMP hydrolysis, while remaining susceptible to inhibition by the combination of two KCa channel blockers, apamin and charybdotoxin. Analogous endothelium- and cAMP-dependent relaxations were evoked by cyclopiazonic acid (CPA) which stimulates Ca2+ influx via channels linked to the depletion of Ca2+ stores. Responses to ACh and CPA were both inhibited by interrupting cell-to-cell coupling via gap junctions with 18α-glycyrrhetinic acid and a connexin-specific Gap 27 peptide. The findings suggest that EDHF-type responses are initiated by capacitative Ca2+ influx into the endothelium and propagated by direct intercellular communication to effect relaxation via cAMP/PKA-dependent phosphorylation events in smooth muscle.

Georg von Békésy, Nobel Laureate in Physiology, Experimental Physicist and Art Collector was Born 100 Years Ago

Georg von Bekesy was born one hundred years ago, on July 3, 1899 in Budapest, Hungary. He graduated from the University of Bern as a chemist in 1921. He received a Ph.D. in physics in Budapest under the supervision of Charles Tangl in 1923. From 1926 to 1947 he worked in Hungary's best-equipped research laboratory, in the Postal Experimental Institution as a postal engineer. Here he lead basic physical research on ear preparations and on realistic models of the ear, made by himself, to investigate the structure and the working of the ear and, first of all, theinner ear (cochlea). For the results of his research in Hungary, Bekesy received the Nobel Prize in Physiology in 1961. The paper also introduces Georg von Bekesy as a passionate art collector and expert.

Ear-piercing techniques as a cause of auricular chondritis.

To investigate the different methods of ear and body piercing as possible sources of infection, and to provide a brief literature review of infections resulting from high ear piercing as well as bacterial coverage of common disinfectants used as preparation agents. Two cases of auricular chondritis caused by Pseudomonas are presented. A survey of 14 businesses that pierce ears was conducted using a scheduled interview. Information regarding the type of piercing instrument, composition of earring, training of employees, anatomic placement of earrings, and preparation and aftercare of ears was obtained. One hundred percent of the interviews attempted were completed. The cosmetic shops and earring kiosks both used hand-powered earring "guns" to pierce ears, while the tattoo parlors used sterile needles and forceps. All of the businesses interviewed used earrings composed of either 14K or 24K gold, stainless steel, and other piercing-grade metals. None of the businesses used earrings made of nickel. The cosmetic shops and kiosks used a combination of videos, demonstrations, and direct supervision to train employees but did not have a specified training period. The tattoo parlors required their employees to complete an apprenticeship training program of varying time lengths. All of the businesses pierced the lobe and cartilaginous portions of the ear. The cosmetic shops and kiosks used benzalkonium chloride or isopropyl alcohol as ear preparation agents, while the tattoo parlors used only iodine-based solutions. At all of the businesses, minimal aftercare instructions were given and they typically dealt with maintaining ear-hole patency. The cosmetic shops and earring kiosks used piercing methods that predisposed to auricular chondritis, such as poor training of employees and use of benzalkonium chloride as a preparation agent. Emergency physicians need to be aware of the severity of these types of infections, which often require surgical management and intravenous antibiotics covering Pseudomonas.

Endogenous nitric oxide influences arteriovenous anastomosis adrenergic tone in the conscious rabbit ear.

The role of nitric oxide (NO) in the control of arteriovenous anastomoses (AVAs) has not been studied in vivo in a thermoregulatory end organ. In this study, the effect of local inhibition of NO synthesis by NG-nitro-L-arginine methyl ester (L-NAME) on the microvasculature in the rabbit ear (n=12) was observed in vivo through a chronically implanted ear microvascular chamber. Ear cutaneous blood perfusion (CBP), total auricular arterial flow (TAF), and ear temperature were monitored simultaneously with the direct microvascular observations. Results revealed that intrafacial artery infusion of L-NAME produced significant vasoconstriction of arterioles, AVAs, and venules (p < 0.05). A decrease of ear blood perfusion also was demonstrated by changes of CBP, TAF, and surface temperature. The data provide evidence that basal generation of NO influences the vascular resistance in the thermoregulatory end organ. Moreover, endogenous NO production may be more important in regulating the AVA flow than is flow in other parts of the rabbit ear microvasculature. The effects of NO inhibition on ear microvasculature were not abolished by superior cervical ganglionectomy, indicating that NO production in the rabbit ear is not a neurally mediated mechanism. Further study with a short-term rabbit ear preparation showed that inhibition of NO production with L-NAME enhanced microvascular constrictive responses to extraluminal application of norepinephrine. NO thus appears to play a role of basal vasodilator in opposition to the basal adrenergic vasoconstrictor tone in the rabbit ear.

Effect of cooling on cutaneous microvascular adrenoceptors in vivo in the rabbit ear.

Previous studies have suggested that moderate cooling increases the responsiveness of vascular alpha2-adrenoceptors. However, limited information is available documenting the influence of temperature changes on adrenoceptor responses in the microvasculature of thermoregulatory organs (e.g., the human digit and the rabbit ear) subjected to a wide range of temperatures. In the present study, the effect of local cooling (24 degrees C) on cutaneous microvascular adrenoceptors in the ear was observed in vivo in male New Zealand White rabbits (total: 66 ears). The rabbit ear was studied in a temperature-controlled tissue bath; the ear preparation was pretreated with terazosin (an alpha1-adrenoceptor antagonist) (10(-5) M) or a combination of terazosin (10(-5) M) and propranolol (a beta-adrenoceptor antagonist) (10(-6) M). The microvascular diameter responses of the ear to norepinephrine (10(-11)-10(-4) M) then were determined at 24 or 34 degrees C, respectively, to determine the influences of low temperature on adrenoceptor responses to norepinephrine stimulation. The results demonstrated that low concentrations of norepinephrine induced vasodilation in arterioles and arteriovenous anastomoses. This vasodilation was followed by vasoconstriction with an increased concentration of norepinephrine in animals with alpha1-adrenergic blockade at 34 degrees C. Moderate tissue cooling increased the microvascular maximal response of the rabbit ear to norepinephrine and abolished the vasodilatation induced by a low concentration of norepinephrine. There was no significant difference in the microvascular response to norepinephrine between the two temperature conditions after simultaneous blockade of alpha1-adrenoceptors and beta-adrenoceptors. Data from the present study indicate that moderate cooling does not enhance the responsiveness of alpha2-adrenoceptors to norepinephrine. In contrast, cooling reduced the beta-adrenergic activity of arterioles and arteriovenous anastomoses after norepinephrine stimulation.

Schultz-dale reaction in isolated perfused calf ear and its inhibition by isoproterenol

Calf ears which were sensitised to horse serum and others which were unsensitised were catheterised and perfused at a constant flow rate of 2 ml min −1 with Krebs-Henseleit solution using a peristalic pump. The ear preparations were then challenged with whole horse serum, the sensitising antigen. Vascular responses were monitored as changes in perfusion pressure. Weight changes were determined to indicate the extent of oedema formation. Unsensitised ear preparations responded to 0·1 ml whole horse serum with 43·3±0·8 per cent (n=5) and 10·7±0·3 per cent (n=5) increases in perfusion pressure and weight, respectively. Sensitised ear preparations responded to 0·05 ml whole horse serum by increases of 280·8±32·9 per cent (n=5) and 27·2±1·4 per cent (n=5) in perfusion pressure and bodyweight, respectively. Isoproterenol (10 −5 M) inhibited the vascular responses by 81·4±7·6 per cent (n=5) while the increases in weight were reduced by 20·0±1·5 per cent (n=5). The Schultz-Dale reaction has thus been demonstrated in an isolated whole organ, the pinna.

Calcium-Induced Vasodilation Due to Increase in Nitric Oxide Formation in the Vascular Bed of Rabbit Ear Preparation

Participation of calcium-induced vasodilation (due to an increase in synthesized nitric oxide (NO) content in endothelial cells) in the arterio-venous circulation, including the vascular bed was investigated by the vessel perfusion method in the isolated rabbit ear preparation. The perfusion medium used was a tris-buffered solution. When CaCl2 (6.25, 12.5 and 25 mg) was injected in the perfused vessel of the rabbit ear preparation, dose-dependent vasocontraction was observed when vascular tone was kept at a normal level. However, CaCl2 dose-dependently induced vasodilation of the vessel when it was continuously contracted by norepinephrine (1.2 x 10(-7) M). This calcium-induced vasodilation was inhibited in the presence of NG-nitro-L-arginine (5 x 10(-5) M), a selective inhibitor of NO synthesis, and methylene blue, a guanylate cyclase inhibitor, although it was rarely affected by indomethacin (10(-5) M), a cyclooxygenase inhibitor. Calcium-induced vasodilation was also obtained in the in situ circulation containing vascular bed, and this suggests that the vasodilation was due to a Ca(2+)-induced increase in the synthesis of NO derived from endothelial cells.

Differential effects of l‐arginine on the inhibition by NG‐nitro‐l‐arginine methyl ester of basal and agonist‐stimulated EDRF activity

1. An isolated, buffer-perfused rabbit ear preparation was used to investigate the influence of NG-nitro-L-arginine methyl ester (L-NAME) on endothelium-dependent vasodiltation and modulation of vasoconstrictor responses and vascular conductance. 2. Acetylcholine (0.55 pmol-1.6 nmol) caused dose-related vasodilatation of preparations constricted by the combination of 5-hydroxytryptamine and histamine (both 1 microM), with an ED50 = 31.1 +/- 7.8 pmol and a maximum dilatation of 69.9 +/- 4.3%. In the presence of 10 microM L-NAME the dose-response for vasodilator effects was shifted significantly (P less than 0.001) to the right (ED50 = 3.07 +/- 1.18 nmol) and there was a significant (P less than 0.01) depression of the maximum response (Rmax = 44.3 +/- 4.0%). The higher concentration of 100 microM L-NAME completely abolished vasodilatation to acetylcholine. L-Arginine (10 mM) did not reverse the inhibitory actions of L-NAME at either concentration. 3. L-NAME 100 microM, augmented vascular tone induced by 1 microM 5-hydroxytryptamine and 1 microM histamine, thus altering the characteristics of both pressure/flow and conductance/flow relationships such that conductance was reduced at all flow rates. The augmentation of constrictor tone was reversed in a concentration-dependent manner by L-arginine (10 microM-10 mM) and the effect of L-NAME on the conductance/flow relationships was similarly reversed by 10 mM L-arginine. The augmentation of tone was endothelium-dependent as it did not occur following functional destruction of the endothelium by perfusion of the vascular bed with the detergent CHAPS (0.3%) for 150s. 4. In conclusion, L-NAME is a potent inhibitor of agonist-induced endothelium-dependent vasodilatation. L-NAME reduces vascular conductance in pharmacologically constricted preparations and this emphasizes the important role of EDRF in vascular regulation. The ability of L-arginine to reverse L-NAME-induced inhibition of basal EDRF activity but not L-NAME-induced inhibition of agonistinduced endothelium-dependent relaxations suggests that there is pharmacological heterogeneity in the mechanisms responsible for the conversion of L-arginine to EDRF.