Diseases of the Ear: General Principles Of Management

The therapeutic plan for otitis externa requires identification of the primary disease process and perpetuating factors. Ideally management is aimed at thoroughly cleaning and drying the ear canal, removing or managing the primary factors, controlling perpetuating factors, administering appropriate topical or systemic therapy (or both), and evaluating response to therapy.

Ear Cleaning

Ear cleaning serves several functions: (1) it removes material that supports or perpetuates infection; (2) it removes bacterial toxins, white blood cells (WBCs), and free fatty acids that stimulate inflammation; (3) it allows complete evaluation of the external ear canal and tympanum; (4) it allows topical therapy to contact all portions of the ear canal; and (5) it removes material that may inactivate topical medications. Significandy painful ears may benefit from initial anti-inflammatory therapy to decrease pain and swelling of the ear canal prior to cleaning. Severe cases of otitis externa often require general anesthesia to facilitate complete cleaning and evaluation of the external and middle ear.

Many different solutions are available for removing cerumen, exudate, and debris from the ear canal (Table Otic Cleaning Solutions). If the tympanic membrane cannot be visualized, only physiologic saline solution or water should be used, because many topical cleaning agents are ototoxic or incite inflammation of the middle ear. An operating otoscope, ear loops, and alligator forceps facilitate manual removal of large amounts of cerumen or debris. Debris is carefully removed under direct visualization, and care is taken deeper in the ear canal (close to the tympanic membrane). Aggressive hair removal is not advised, because inflammation and damage to the epithelium can result in secondary bacterial colonization and infection. Flushing may be performed after large accumulations of cerumen and debris are mechanically removed from the ear canal.

Otic Cleaning Solutions

Trade Name Acetic Acid Boric Acid Salicylic Acid Isopropyl Alcohol Propylene Clycol Dss Other
Ace-Otic Cleanser 2%   0.1%       Lactic acid 2.7%
Adams Pan-Otic         X X Parachlorometaxylenol, tris EDTA, methylparaben, diazolidinyl urea, popylparaben, octoxynol
Alocetic Ear Rinse X     X     Nonoxynol-12, methylparaben, alovera gel
Cerulytic Ear Ceruminolytic         X   Benzyl alcohol, butylated hydroxytoluene
Cerumene             25% Isopropyl myristate
DermaPet Ear/Skin Cleanser for Pets X X          
Docusate Solution         X X  
Earmed Boracetic Flush X X         Aloe
Earmed Cleansing Solution & Wash         X   50A 40B alcohol, cocamidopropyl phosphatidyl and PE dimonium chloride
Earoxide Ear Cleanser             Carbamide peroxide 6.5%
Epi-Otic Ear Cleanser     X   X X Lactic acid, chitosanide
Fresh-Ear X X X X X   Lidocaine hydrochloride, glycerin, sodium docusate, lanolin oil
OtiCalm     X       Benzoic acid, malic acid, oil of eucalyptus
Otic Clear X X X X X   Glycerin, lidocaine hydrochloride
Oticlean-A Ear Cleaning Lotion X X X 35% X   Lanolin oil, glycerin
Oti-Clens     X   X   Malic acid, benzoic acid
Otipan Cleansing Solution         X   Hydroxypropyl cellulose, octoxynol
Otocetic Solution 2% 2%          
Wax-O-Sol 25%             Hexamethyltetracosane

Flushing and evacuation of solution is done under direct visualization through an operating otoscope. A bulb syringe and red rubber catheter system may be used to both flush and evacuate solutions and accumulations from the ear canal. The operator, avoiding drastic pressure changes within the external ear canal that could damage the tympanum, should carefully control suction and manual evacuation of the contents of the bulb syringe from the ear canal. Other alternatives include tomcat catheters (3.5 F) or flexible, intravenous catheters (14 gauge, Teflon); stiff, narrow catheters should be used cautiously and under direct visualization deep in the external ear canal. Other reservoir systems for delivery or evacuation of solutions include a 12 mL syringe or suction tubing attached to in-house vacuum systems. In-house vacuum systems should be used cautiously and under direct visualization. Care should be taken to avoid trauma to the tympanic membrane until its integrity can be assessed. Initial flushes should be done with physiologic saline solution or water until the integrity of the tympanic membrane is established.

Other solutions may aid in the removal of wax in the ear canal. Ceruminolytics are emulsifiers and surfactants that break down ceruminocellular aggregates by causing lysis of squamous cells. A ceruminolytic agent in an alkaline pH may more effectively lyse squamous cells via cell surface protein disruption. Oil-based products soften and loosen debris to aid in their removal but do not cause cell lysis. Water-based ceruminolytics are easier to remove and dry more quickly than oil-based solutions, which are occlusive if they remain in the ear canal. Water-based products include dioctyl sodium sulfosuccinate, calcium sulfosuccinate, and carbamate peroxide, which has a foaming action with the release of urea and oxygen. Oil-based products include squalene, triethanolamine polypeptide, hexamethyltetracosane, oleate condensate, propylene glycol, glycerin, and mineral oil. In a recent study only the combination of squalene and isopropyl myristate in a liquid petrolatum base had no adverse effects on hearing, the vestibular system, and histopathologic examination. Other agents tested contained glycerin, dioctyl sodium sulfosuccinate (2% or 6.5%), parachlorometaxylenol, carbamide peroxide (6%), propylene glycol, triethanolamine polypeptide oleate condensate (10%), and chlorobutanol (0.5%).

Alcohol-based drying agents added to ceruminolytics include boric acid, benzoic acid, and salicylic acid, which decrease the pH of the ear canal, cause keratolysis, and have a mild antimicrobial effect. Drying the ear canal is important to combat increased humidity, which potentiates infection.

If the tympanum is intact, the ear canal is filled with a ceruminolytic agent for at least 2 minutes and the pinna is cleaned at the same time. The solution is flushed twice with warm water, and the canal inspected. The procedure is repeated until cleaning is complete. Other solutions commonly advocated for ear flushing include dilute chlorhexidine solution (0.05%), dilute povidone-iodine, and acetic acid (2.5%). The first two agents are potentially ototoxic or induce inflammation and should not be used if the tympanum is ruptured. A combination of propylene glycol malic, benzoic, or salicylic acid; 2% acetic acid; or dilute povidone-iodine have been suggested for use in dogs with a ruptured tympanum.

Owners may clean the ears at home with mild preparations of ceruminolytics and drying agents if mild otitis is present without severe accumulation of cerumen or exudate. Aqueous solutions are usually recommended because they are less occlusive and easier to clean from the ear, dog, and home environment.

The ear should be filled with the solution, then massaged for 40 to 60 seconds. The pet should be allowed to shake its head to remove the majority of the solution, and the excess should be wiped from the ear canal and pinna with a tissue. Daily flushing is usually recommended, followed by every other day, weekly, then as needed, depending on the solution. Ear swabs are not recommended for home use, because cerumen and debris may be forced into the horizontal ear canal and impact against the tympanic membrane

Topical Therapy

Erythematous ceruminous otitis externa is diagnosed 2.7 times more often than acute suppurative otitis according to one report. Yeast ± cocci were identified in those cases, with cocci or rods identified in suppurative otitis. Topical therapy should be based on the cytologic examination to diminish the incidence of inappropriate treatment (Table Topical Medications Used in the Treatment of Ear Disease). Many preparations combine anti-inflammatories and antimicrobials in an attempt to decrease the inflammation and combat bacterial or yeast overgrowth. All topical medications should be considered supportive, and specific treatment should be aimed at controlling the primary disease process.

Topical Medications Used in the Treatment of Ear Disease

Generic Name Trade Name Dose Frequency Description
Fluocinolone 0.01% DMSO 60% Synotic 4-6 drops; total dose<17mL q12h initially. q48-72h maintenance Potent corticosteroid anti-inflammatory
Hydrocortisone 1.0% HB101,

Burrows H,

2-12 drops, depending on ear size q12h initially. q24-48h maintenance Mild corticosteroid anti-inflammatory
Hydrocortisone 1.0%, lactic acid Epiotic HC 5-10 drops q12h for 5 days Mild corticosteroid anti-inflammatory, drying agent
Hydrocortisone 0.5%, sulfur 2%. acetic acid 2.5% Clear X Ear Treatment 2-12 drops, depending on ear size q12-24h initially. q24-48h maintenance Mild corticosteroid anti-inflammatory, astringent, germicidal
DSS 6.5%. urea (carbamide peroxide 6%) Clear X Ear Cleansing Solution 1-2 mL per ear Once per week to as necessary Ceruminolytic, lubricating agent
Chlorhexidine 2% Nolvasan Dilute 1:40 in water As necessary Antibacterial & antifungal activity
Chlorhexidine 1.5% Nolvasan Dilute 2% in

propylene glycol

q12h Antibacterial & antifungal activity
Povidone-iodine 10% Betadine solution Dilute 1:10-1:50 in water As necessary Antibacterial activity
Polyhydroxidine iodine 0.5% Xenodyne Dilute 1:1-1:5 in water As necessary, q12h, once weekly Antibacterial activity
Acetic acid 5% White vinegar Dilute 1:1-1:3 in water As necessary; q12-24h for Pseudomonas Antibacterial activity, lowers ear canal pH
Neomycin 0.25%, triamcinolone 0.1%, thiabendazole 4% Tresaderm 2-12 drops depending on ear size q12h up to 7 days Antibacterial & antifungal activity, parasiticide (mites), moderate corticosteroid anti-inflammatory
Neomycin 0.25%, triamcinolone 0.1%, nystatin 100,000 U/mL Panalog 2-12 drops depending on ear size q12h to once weekly Antibacterial & antifungal activity, moderate corticosteroid anti-inflammatory
Chloramphenicol 0.42%. prednisone 0.17%, tetracaine 2%, squalene Liquachlor, Chlora-Otic 2-12 drops depending on ear size q12h up to 7 days Antibacterial activity, mild corticosteroid anti-inflammatory
Neomycin 1.75 & polymyxin B 5000 lU/mL, penicillin C procaine 10,000 lU/mL Forte Topical 2-12 drops depending on ear size q12h Antibacterial activity
Centamicin 0.3%, betamethasone valerate 0.1% Centocin Otic Solution, Betagen Otic Solution 2-12 drops depending on ear size q12h for 7 to 14 days Antibacterial activity, potent corticosteroid anti-inflammatory
Centamicin 0.3%, betamethasone 0.1%, clotrimazole 0.1% Otomax, Obibiotic Ointment 2-12 drops depending on ear size q12h for 7 days Antibacterial & antifungal activity, potent corticosteroid anti-inflammatory
Centamicin 0.3%, betamethasone valerate 0.1%, acetic acid 2.5% Centaved Otic Solution 2-12 drops, depending on ear size q12h for 7 to 14 days Antibacterial activity, potent corticosteroid anti-inflammatory
Polymixin B 10,000 lU/mL, hydrocortisone 0.5% Otobiotic 2-12 drops, depending on ear size q12h Antibacterial activity, mild corticosteroid anti-inflammatory
Enrofloxacin 0.5%, silver sulfadiazine 1% Baytril Otic 2-12 drops, depending on ear size q12h for up to 14 days Antibacterial activity
Carbaryl 0.5%, neomycin 0.5%, tetracaine Mitox Liquid 2-12 drops, depending on ear size   Antibacterial activity, parasiticide (mites)
Pyrethrins 0.06%, piperonyl butoxide 0.6% Ear Mite and Tick Control 5 drops q12h Parasiticide (mites)
Pyrethrins 0.05%, squalene 25% Cerumite 2-12 drops, depending on ear size q24h for 7 to 10 days Parasiticide (mites), ceruminolytic
Isopropyl alcohol 90%, boric acid 2% Panodry Fill ear canal As necessary Drying agent
Acetic acid 2%, aluminum acetate Otic Domeboro Fill ear canal q12-48h Drying agent, antibacterial activity, lowers ear canal pH
Silver sulfadiazine Silvadene Dilute 1:1 with water, 1 g powder in 100 mL water q12h for 14 days Antibacterial & antifungal activity
Tris EDTA±

gentamicin 0.03%

  2-12 drops, depending on ear size q12h for 14 days 1 L distilled water, 1.2g Tris EDTA, 1 mL glacial acetic acid; antibacterial activity
Silver nitrate   Use sparingly As necessary Cauterization of

ulcerative otitis externa

Miconazole 1%; ± topical glucocorticoid (7.5 mL of dexamethasone phosphate (4 mg/mL] to10mLof1% miconazole) Conofite 2-12 drops, depending on ear size q12-24h Antifungal activity
Ivermectin 0.01% Acarexx 0.5 mL per ear Once Parasiticide (mites)
Pyrethrins 0.15%, piperonyl butoxide 1.5% Many 2-12 drops, depending on ear size Twice at 7-day interval Parasiticide (mites)
Pyrethrins 0.05%, piperonyl butoxide 0.5%, squalene 25% Cerumite 2-12 drops, depending on ear size q24h for 7 days Parasiticide (mites), ceruminolytic
Pyrethrins 0.04%, piperonyl butoxide 0.49%, DSS 1.952%, benzocaine 1.952% Aurimite 10 drops q12h  
Rotenone 0.12%, cube resins 0.16% Many 2-12 drops, depending on ear size Every other day Parasiticide (mites)

Topical glucocorticoids benefit most cases of otitis externa by decreasing pruritus, exudation, swelling, and proliferative changes of the ear canal. The most potent glucocorticoids available in topical preparations are betamethasone valerate and fluocinolone acetonide. Less potent corticosteroids include triamcinolone acetonide and dexamethasone; the least potent is hydrocortisone. Most dogs benefit from short-term therapy with topical corticosteroids at the initiation of therapy, with concurrent therapy aimed at the primary and other perpetuating factors. Long-term therapy with topical corticosteroids can be deleterious because of systemic absorption of drug. Increased serum liver enzymes and depressed adrenal responsiveness may occur; with prolonged use iatrogenic hyperadreno-corticism is possible. Glucocorticoids alone may be of benefit for short-term therapy in cases of allergic or erythematous ceruminous otitis.

Antimicrobials are important for controlling secondary bacterial or yeast overgrowth or infection. Antimicrobials are indicated in any case with cytologic evidence of bacterial overgrowth or infection, with attention paid to the morphology and gram-staining characteristics of the bacteria. Otic preparations commonly contain aminoglycoside antibiotics. Neomycin is effective against typical otitis bacteria such as Staphylococcus intermedium. Gentamicin and polymyxin B are also appropriate initial topical treatments for gram-negative bacterial otitis externa.The significant risk of bone marrow toxicity in people limits the use of chloramphenicol for treating otitis in dogs and cats despite its antibacterial spectrum and availability.

Due to the frequency of resistant gram-negative bacteria such as Pseudomonas, other topical preparations have been developed. Enrofloxacin, ophthalmic tobramycin, and topical application of injectable ticarcillin have been used to treat otitis in dogs.< Their use should be limited to cases of resistant bacteria, and culture and susceptibility testing should be performed prior to application. Other topical agents may be used to supplement treatment of resistant Pseudomonas, such as silver sulfadiazine solution and tris EDTA. Tris EDTA can render Pseudomonas susceptible to enrofloxacin or cephalosporins by enhancing membrane permeability and altering ribosome stability. Frequent ear cleaning may also assist in the treatment of resistant bacterial otitis; ceruminolytics have antimicrobial properties, and their use in clinical cases has been evaluated. Acetic acid in combination with boric acid is effective against both Pseudomonas and Staphylococcus, depending on concentration and duration of exposure. Ear cleaning removes proinflammatory products, cells, and substances that diminish the effectiveness of topical antibiotics.

Many topical preparations control yeast organisms, which may complicate erythematous ceruminous otitis and suppurative otitis. Common active ingredients include miconazole, clotrimazole, nystatin, and thiabendazole. Preparations containing climbazole, econazole, and ketoconazole have also been evaluated. Eighty percent of yeast were susceptible to miconazole and econazole, intermediately resistant to ketoconazole, and 90% were resistant to nystatin and amphotericin B in one in vitro study. Topical ear cleaning agents have some efficacy against Malassezia organisms. Other preparations (e.g. chlorhexidine, povidone-iodine, acetic acid) are also effective in the treatment of secondary yeast overgrowth.

Response to topical therapy should be gauged by re-evaluation of physical, cytologic, and otoscopic examinations every 10 to 14 days after the initiation of therapy. Any changes in the results of these examinations should be recorded. Most cases of otitis can be managed topically; failure to respond to therapy should prompt re-evaluation of the diagnosis and treatment.

Systemic Therapy

Systemic glucocorticoid administration may be beneficial in cases of severe, acute inflammation of the ear canal, chronic proliferative changes of the ear canal, and allergic otitis. Anti-inflammatory doses should be limited to 7 to 10 days. Cases of significant thickening or proliferative changes in the external ear canal benefit from systemic antimicrobial therapy. Systemic therapy should be considered if concurrent dermatologic changes of the surrounding skin, pinna, or other regions of the body are present. Long-term administration of appropriate antimicrobials based on culture and susceptibility is required in all cases of otitis media. Systemic therapy for yeast is rarely recommended in animals with otitis alone. One study evaluated oral itraconazole therapy, and in ear samples evaluated on cytology and culture, no change in cytology score was found.



Treatment of Cutaneous Lymphosarcoma

Glucocorticoids remain the mainstay of treatment of cutaneous T cell-rich, B cell lymphoma. Tumor regression is typically noted following the systemic administration of dexamethasone (0.02-0.2 mg/kg IV, IM or PO q24h) or prednisolone (1-2 mg/kg PO q24h). In these authors’ experience, dexamethasone proves more effective than prednisolone in treating lymphosarcoma. Once cutaneous lesions have regressed in size and number, the glucocorticosteroid dose can be gradually tapered. However, a rapid decrease or discontinuation of glucocorticosteroid administration may result in recurrence of cutaneous lesions. Relapses are anecdotally reported to be sometimes more refractory to treatment. Long-term maintenance therapy may be required in these cases. These authors prefer to use a dose of 0.04 mg/kg of dexamethasone (approximately 20 mg for an average-size horse) once daily until significant regression of tumors has occurred; the dose then is reduced to 0.02 mg/kg daily and then to every 48 hours. Intralesional injections of betamethasone or triamcinolone can also be performed with success; this may be impractical when presented with a large number of cutaneous lesions. Topical application of corticosteroid preparations may result in clinical improvement in cases with ulceration; however, results of its use have not been reported. In addition to im-munosuppression, laminitis is a potential side effect of corticosteroid administration.

Exogenous progestins may demonstrate an antiproliferative effect on lymphosarcoma tumors. The exact mechanism of action has not been determined; however, it is believed to be due to the presence of progesterone receptors, which have been demonstrated on both neoplastic and normal equine lymphoid tissues. Progestogens also have glucocorticoid-like activity, which may also account for the response observed in some cases of lymphosarcoma. In one study, progesterone receptors were identified on 67% of the subcutaneous lymphosarcoma tumors that were evaluated (primarily representing T cell-rich, B cell tumors). In the mare diagnosed with simultaneous cutaneous histiolymphocytic lymphosarcoma and a granulosatheca cell ovarian tumor, partial regression of the skin lesions occurred following a ten-day course of the synthetic progestin, altrenogest (0.044 mg/kg q24h PO). A temporary response was also observed after unilateral ovariectomy. The ovarian tumor stained positive for estradiol and led the authors to believe it was estrogen-secreting. The authors speculated that the steroid hormones secreted by the ovarian tumor may have influenced growth of the T cell-rich, B cell tumors by leading to low progesterone concentrations. Anecdotal reports of tumor regression during pregnancy also exist. In one mare with cutaneous T cell lymphosarcoma, regression of nodules was noted after surgical excision, a single intralesional injection of betamethasone (0.04 mg/kg), and an 8-day course of the oral progestogen, megestrol acetate (0.2 mg/kg q24h). Surgical excision may be efficacious in cases in which a single or a small number of cutaneous nodules exists.

The administration of autologous tumor cell vaccines may benefit horses with cutaneous lymphosarcoma. In one report, tumor regression was achieved by using a combination of low-dose cyclophosphamide and autologous tumor cells infected with vaccinia virus. Cyclophosphamide is thought to potentiate the immune response by decreasing suppressor T cell activity. Infection of tumor cells with the vaccinia virus was performed to augment the host antitumor immune response. The treatment protocol included intravenous administration of cyclophosphamide (300 mg/m2) via a jugular catheter over a period of 2 to 3 minutes on days 1 and 36. Immunization with tumor-cell vaccine was performed on days 4 and 21. Response to immunostimulation was confirmed by development of a delayed-type hypersensitivity response to autologous tumor cells injected intradermally in the horse. Potential side effects of cyclophosphamide administration in other species include immunosuppression, enterocolitis, myelosuppression, and hemorrhagic cystitis. No side effects were noted in the horse in this report.

Treatment of epitheliotropic (cutaneous T cell lymphosarcoma) in horses remains speculative because of a paucity of reported cases. Surgical excision of small lesions may be curative. Retinoids and vitamin A analogs inhibit malignant lymphocyte proliferation in human and canine patients with epitheliotropic lymphosarcoma. No reports of the use of retinoids in horses have been published. However, these authors noted no gross or histologic improvement in treating one case of equine epitheliotropic lymphosarcoma with retinoid cream. Side effects included local erythema and signs of irritation after repeated applications.

Investigations as to the effectiveness of radiation therapy and systemic chemotherapy in the management of equine cutaneous lymphosarcoma are needed. Local therapy that consists of intralesional injection of cutaneous nodules with cisplatin has been used successfully in horses with a small number of lesions. Combination chemotherapy that consists of cytosine arabinoside, chlorambucil or cyclophosphamide, prednisone, and vincristine has been reported for use in horses with multicentric lymphosarcoma, as has L-asparaginase.


Treatment of Pastern Dermatitis

The appropriate therapy obviously involves identification of the predisposing, perpetuating, and primary factors. In general, avoiding pastures/paddocks with mud, water, or sand may minimize predisposing factors. Keeping patients stalled during wet weather and until morning dew has dried is often rewarding. Use of alternate sources of bedding may be beneficial because the chemicals in treated or aromatic types of wood shavings may result in contact dermatitis. Lastly, clip hairs — especially feathers — to avoid moisture retention.

Perpetuating factors should be addressed according to the severity of the condition. The most conservative approach includes cleansing lesions with antimicrobial shampoos (benzoyl peroxides, chlorhexidine, ethyl lactate, imidazoles) twice daily for 7 to 10 days and then tapering in frequency. If a dry environment is not possible, the affected pastern areas can be protected with ointments (creating a moisture barrier); with padded and water-repellent bandages (changed q24-48h); or with Facilitator, a hydroxy-ethylated amylopectin liquid bandage that is replenished every 1 to 3 days. If the lesions are exudative, astringent solutions — such as lime sulfur (LymDyp), aluminum acetate solutions, black tea bag or sauerkraut poultices, or acetic acid/boric acid wipes (Malacetic Wipes, Dermapet Inc., West Plains, Mo.) — should be used after cleansing.

Topical sprays, creams, or ointments that contain antibiotics, steroids, antifungal agents, or a combination thereof may benefit the patient, depending on the diagnosis. A 2% mupirocin ointment (Bactoderm), with excellent tissue penetration, is the author’s preference for addressing localized dermatophilosis and bacterial dermatitis. A DMSO / thiabendazole / sulfa ointment has also been described in the fourth edition of Current Therapy in Equine Medicine. If generalized to all four limbs, treatment of the bacterial dermatitis is best accomplished with daily systemic antibiotics (trimethoprim/sulfa 30 mg/kg/day or cephalexin 22 mg/kg q8hrs) until 7 days after clinical resolution.

Lime sulfur dips and chlorhexidine / imidazole-containing shampoos, sprays, and residual leave-on products comprise the current antifungal arsenal in veterinary medicine. Topical enilconazole (Imaverol), labeled for use in horses in various countries other than the United States, has been used to treat fungal infections with reported success. Many veterinary dermatologists feel that systemic griseofulvin lacks efficacy for the treatment of equine dermatophytosis.

Ectoparasiticidal therapy consists of avermectins, topical organophosphates (malathion, coumaphos), pyrethroids (permethrin, flumethrin), lime sulfur, and fipronil (Frontline). The latter has had recent success in the treatment of Chorioptes bovis within a group of heavier cob and draught-cross horses. Of note was the ability of the parasite to survive off the host, enduring solely in the presence of skin debris in a moist and dark environment and thus emphasizing the need for environmental management to prevent recurrence.

Immunomodulators have been used for the condition. Interferon-a2a given at 1000 IU/ml on a cycle of 1.0 ml per horse daily for 3 weeks and then off for 1 week has been used by the author to help stimulate the local immune defense system, with very little cost or side effects. Immune-mediated conditions such as PLV, however, require a significant immunosuppressive effort to achieve resolution and control of the clinical signs. High-dose glucocorticoids, preferably dexamethasone (0.1-0.2 mg/kg q24h for 7-14 days, then taper over the next 4-6 weeks), along with reduction of UV light exposure by stabling or covering with a light bandage, appears to control — if not resolve-many cases. Should resolution of clinical signs not be achieved by 14 days, the author has achieved excellent results by adding pentoxifylline (PTX), a phosphodiesterase inhibitor. PTX has been reported to have multiple immunomodulatory effects that potentiate the effectiveness of traditional immunosuppressive drugs (i.e., steroid-sparing effect). These include inhibition of lymphocyte activation and proliferation; increased lymphocyte suppression; suppression of tumor necrosis factor (TNF)-a, lymphotoxin, and interferon-7 production; and upregulation of IL-10 mRNA that leads to increased IL-10 serum levels. Oral absorption varies considerably between individuals; thus reported dosages range between 4 to 8 mg/kg every 12 hours.

Once the skin has returned to normal, long-term control of PLV may be achieved by a combination of topical steroids (betamethasone valerate 0.1%, aclometasone 0.05%), coupled with an every other day systemic regimen of PTX and, if necessary, low-dose dexamethasone on an alternate day basis.

The prognosis and healing time of equine pastern dermatitis depends on the stage of disease when treatment begins and on the ability to identify the etiology. Ensuring that predisposing, primary, and perpetuating factors are encompassed in a diagnostic and treatment plan will optimize the likelihood of a positive outcome.

Veterinary Drugs


The anti-inflammatory effects of corticosteroids are based upon their ability to suppress capillary dilatation, vascular exudation, leucocyte migration, and immunosuppression regardless of the causative agent. In chronic conditions they inhibit neovascularisation and fibroblastic activity in the eye. This may be useful in preventing scarring and pigment deposition in the cornea but disadvantageous by retarding healing. In general, topical preparations readily penetrate the cornea. The ester of the corticosteroid used influences corneal penetration, for example, prednisolone acetate has a superior corneal penetration to prednisolone sodium phosphate.

Topical corticosteroids are particularly useful in the treatment of uveitis, various specific and non-specific inflammatory disorders of the cornea, such as chronic superficial keratitis (CSK, pannus) in the German Shepherd dog. They also assist in the reduction of post-surgical inflammation, such as that following cataract or lens extraction. Following administration, therapeutic levels remain in the eye for only about three hours and this may necessitate frequent application to prevent treatment failure. Low levels of systemic absorption will occur after frequent application of topical steroids and this should be considered in animals of low body-weight and those with metabolic diseases such as diabetes mellitus. Topical corticosteroids should not be used in the presence of corneal ulceration; systemic NSAIDs should be considered. Corticosteroids may be used in the presence of glaucoma in animals but care should obviously be taken in the differential diagnosis of a ‘red eye’. All corticosteroids should be used with care in pregnant animals because there is a slight risk of intra-uterine growth retardation.

Subconjunctival injections may augment, or replace, topical instillation. Preparations of methylprednisolone acetate or triamcinolone acetonide may be effective for up to three weeks. Their use may sometimes be effective for owners experiencing difficulty in applying drops. Subconjunctival therapy may be used for the treatment of bovine iritis. Beta-methasone sodium phosphate (2 mg) or dexamethasone sodium phosphate (2 mg) every 3 days or methylprednisolone (10 to 20 mg, depot injection) every 7 to 14 days may be administered by subconjunctival injection for the treatment of inflammatory ocular conditions in horses. However, subconjunctival granulomas, plaques, or mineralisation can occur at the injection site. It is recommended that specialist advice be sought before using subconjunctival corticosteroid treatment in equines. Care must be taken with the use of topical corticosteroids in horses because the alteration in ocular micro-environment can predispose to fungal infections. Similar caution must be exercised in cats with suspected herpetic keratitis because local immunosuppression caused by the corticosteroid can allow recrudescence of the herpes virus. The use of systemic corticosteroids for ophthalmic therapy is limited because lower ocular concentrations are achieved than with topical application. However, systemic therapy may be useful for idiopathic partial serous retinal detachments, posterior uveitis, and optic neuritis. There is an association between cataractogenesis and steroid therapy in humans but this has not been described in animals. The adverse effects of prolonged administration of systemic corticosteroids may be minimised by alternate day therapy. Equine recurrent uveitis (periodic ophthalmia) is a disease of horses resulting in recurrent photophobia, lacrimation, conjunctival injection, corneal changes (such as oedema and vascularisation), hypopyon, miosis, synechiation, and even blindness due to extensive synechiae, cataract formation, or phthisis bulbi. Some forms of the disease have been linked to Leptospira infection, although in many instances the aetiology remains obscure. Treatment consists of topical and possibly subconjunctival corticosteroids, NSAIDs, and if bacterial infection is suspected, systemic antibacterials. Topical atropine is used to achieve a mid-dilated pupil.


Indications. See notes above

Contra-indications. Corneal ulceration, fungal or viral infections, see notes above

Warnings. Care in pregnant animals

Dose: Apply every 2-3 hours

Prescription-only medicine:® Betnesol (Celltech) UK

Drops (for eye, ear, or nose), betamethasone sodium phosphate 0.1%

Eye ointment, betamethasone sodium phosphate 0.1%

Prescription-only medicine: ® Vista-Methasone (Martindale) UK Eye drops, betamethasonesodium phosphate 0.1%


Indications. See notes above

Contra-indications. Corneal ulceration, see notes above

Warnings. Care in pregnant animals

Dose: Apply every 2-3 hours

Prescription-only medicine:® Maxidex(Alcoa) UK

Eye drops, dexamethasone 0.1%, hypromellose 0.5%

Prescription-only medicine: ® Minims Dexamethasone (Chauvin) UK Eye drops, dexamethasone sodium phosphate 0.1%


Indications. See notes above

Contra-indications. Corneal ulceration, see notes above

Warnings. Care in pregnant animals

Dose: Apply 4 times daily

Prescription-only medicine: ® FML (Allergan) UK

Eye drops, fluorometholone 0.1%, polyvinyl alcohol 1.4%


Indications. See notes above

Contra-indications. Corneal ulceration, see notes above

Warnings. Care in pregnant animals

Dose: Apply 4 times daily

Prescription-only medicine: ® Pred Forte (Allergan) UK Eye drops, prednisolone acetate 1%

Prescription-only medicine:® Predsol (Celltech) UK

Drops (eye drops or ear drops), prednisolone sodium phosphate 0.5%

Prescription-only medicine: ® Minims Prednisolone (Chauvin) UK

Eye drops, prednisolone sodium phosphate 0.5% (single use)


Indications. Treatment of local inflammation

Warnings. Care in pregnant animals

Dose: Apply 1 drop 2-4 times daily for up to 4 weeks. May be used more frequently for severe uveitis

Prescription-only medicine:® Vexol (Alcon) UK Eye drops, rimexolone 1%


Preparations containing antibacterial and glucocorticoid agents in combination can be useful in cases of infected inflammatory processes such as bacterial keratitis, and for prophylaxis, for example following intra-ocular surgery where control of inflammation is important but a risk of infection also exists. A specific diagnosis and rationale for combination therapy should always be established.

Indications. See notes above

Contra-indications. Corneal ulceration

Warnings. Care in pregnant animals

Dose: See preparation details

Prescription-only medicine:® Maxitrol (Alcoa) UK

Eye drops, dexamethasone 0.1%, hypromellose 0.5%, neomycin (as suifate) 0.35%, polymyxin B suifate 6000 units/mL

Dose: Apply 4 times daily

Prescription-only medicine:® Maxitrol (Alcon) UK

Eye ointment, dexamethasone 0.1%, neomycin (as suifate) 0.35%, polymyxin B suifate 6000 units/g

Dose: Apply 3 times daily

Prescription-only medicine:® Vista-Methasone N (Martindale) UK

Eye drops, betamethasone sodium phosphate 0.1%, neomycin suifate 0.5%

Veterinary Drugs




Note: For more information refer to the post: Glucocorticoids, General information


A synthetic glucocorticoid, betamethasone is available as the base and as the dipropionate, acetate and sodium phosphate salts. The base is used for oral dosage forms. The sodium phosphate and acetate salts are used in injectable preparations. The dipropionate salt is used in topical formulations and in combination with the sodium phosphate salt in a veterinary-approved injectable preparation. Betamethasone may also be known as flubenisolone.

Betamethasone occurs as an odorless, white to practically white, crystalline powder. It is insoluble in water and practically insoluble in alcohol. The dipropionate salt occurs as a white or creamy-white, odorless powder. It is practically insoluble in water and sparingly soluble in alcohol. The sodium phosphate salt occurs as an odorless, white to practically white, hygroscopic powder. It is freely soluble in water and slightly soluble in alcohol.

Storage – Stability – Compatibility

Betamethasone tablets should be stored in well-closed containers at 2-30°C. The oral solution should be stored in well-closed containers, protected from light and kept at temperatures less than 40°C. The sodium phosphate injection should be protected from light and stored at room temperature (15-30°C); protect from freezing. The combination veterinary injectable product (Betasone®) should be stored between 2 – 30°C and protected from light or freezing.

When betamethasone sodium phosphate was mixed with heparin sodium, hydrocortisone sodium succinate, potassium chloride, vitamin B-complex with C, dextrose 5% in water (D5W), D5 in Ringer’s, D5 in lactated Ringer’s, Ringer’s lactate injection or normal saline, no physical incompatibility was noted immediately or after 4 hours.

Contraindications/Precautions/Adverse effects

For the product Betasone® (Schering), the manufacturer states that the drug is “contraindicated in animals with acute or chronic bacterial infections unless therapeutic doses of an effective antimicrobial agent are used.” See the monograph: Glucocorticoids, General Information for additional information.

In addition to the contraindications, precautions and adverse effects outlined in the opening section of glucocorticoids, betamethasone has been demonstrated to cause decreased sperm output and semen volume and increased percentages of abnormal sperm in dogs.


Doses for dogs:

For the control of pruritis:

a) Betasone® aqueous suspension: 0.25 – 0.5 ml per 20 pounds body weight IM. Dose dependent on severity of condition. May repeat when necessary. Relief averages 3 weeks in duration. Do not exceed more than 4 injections. (Package Insert; Betasone®-Schering)

Dosage Forms/Preparations/Approval Status/Withdrawal Times

Veterinary-Approved Products:

Betamethasone diproprionate equivalent to 5 mg/ml of betamethasone and betamethasone sodium phosphate equivalent to 2 mg/ml betamethasone in 5 ml vials; Betasone® (Schering); (Rx) Approved for use in dogs.

Betamethasone valerate is also found in Gentocin® Otic, Gentocin® Topical Spray and Topagen® Ointment, all from Schering Animal Health.

Human-Approved Products:

Betamethasone sodium phosphate Injection 4 mg/ml (equivalent to 3 mg/ml betamethasone) in 5 ml vials; Celestone Phosphate® (Schering) (Rx); Cel-U-Jec® (Hauck); generic; (Rx)

Betamethasone sodium phosphate Injection 3 mg/ml and betamethasone acetate 3 mg/ml in 5 ml vials; Celestone Soluspan® (Schering); Generic (Rx)

Betamethasone oral solution 0.6 mg/5 ml andBetamethasone tablets 0.6 mg; Celestone® (Schering); (Rx)

Also many topical formulations available.