Skin pharmacology Flashcards
What are the different types of skin barrier treatments?
Emollients
- Soften, lubricate & soothe skin
- Occlusive: seal in water content of stratum corneum –> decreased trans-epidermal water loss
- e.g. lanolin, coconut oil, Vaseline
Moisturisers
- Increase water content of stratum corneum
- e.g. colloidal oatmeal, urea, glycerine, aloe vera
Agents to improve skin barrier function
- e.g. Essential fatty acids & oils
What is the purpose of antiseborrhoeic agents?
Control scale
What are the actions of antiseborrhoeic agents?
Keratolytic → Reduce cohesion between stratum corneum cells
Keratoplastic → Normalise epidermal epithelialisation & keratinisation, reduce epithelial turnover
+- degreasing
e.g. salicylic acid, sulphur
Choice of product affected by whether coat greasy/dry
Aim to use mildest effective product to minimise risk of drying
Why is it important to identify the underlying primary problem in otitis externa?
Ear infections are often secondary to allergies or other conditions
Treating underlying cause is necessary for long-term resolution
How does dysbiosis contribute to otitis externa?
Microbial imbalances precede infection
Early intervention with topical corticosteroids ± antimicrobial cleaners can prevent full infection, reducing need for antibiotics
Why is cytology essential in treating otitis externa?
Helps confirm infectious agent
Guides appropriate treatment selection, preventing unnecessary antibiotic use
What components are commonly found in ear drops/creams?
Antibiotic + antifungal + corticosteroid (polypharmacy)
What factors influence ear treatment selection?
Organism type → Based on cytology/culture
Level of inflammation → Use lowest potency glucocorticoid needed
Potential ototoxicity → Avoid certain drugs if tympanic membrane is ruptured
Nature of exudate → Some antibiotics (e.g. polymyxin B) are inactivated by pus
Frequency of application
What are some key components of ear cleaners?
Cerumenolytics → Dissolve/soften wax (e.g. squalene, mineral oils)
Antimicrobials → Kill/control microbes (e.g. chlorhexidine, acetic acid)
Surfactants → Emulsify debris (e.g. sodium decusate)
Astringents → Dry ear canal (e.g. boric acid, alcohols)
When should ear cleaning be done?
To remove exudate & improve medication efficacy
To manage microbial dysbiosis
For maintenance cleaning (max 1-2x weekly to prevent irritation)
What are the advantages of topical therapy in dermatology?
Higher drug concentration at site of infection
Minimises concerns about side effects associated with systemic drugs (e.g. antibiotics, glucocorticoids)
Targeted action on different areas of skin
What are the challenges of topical therapy?
Labour-intensive → Requires compliance
Formulation considerations → Sprays, wipes, foams may be easier than shampoos
Application difficulty → Hair, location (e.g. eyes, head) may hinder use
Risk of ingestion → Some drugs may be toxic if licked off
Some animals won’t tolerate
What are key principles when using antimicrobials for skin infections?
Confirm bacterial involvement – always do cytology where possible
Avoid unnecessary antibiotic use – not suitable for Malassezia dermatitis, pruritus, or ectoparasites
Use topical treatments when possible
Choose narrow-spectrum antibiotics & lowest EMA Category drug
Address underlying cause for long-term resolution
What are the first steps in managing bite and traumatic wounds in small animals?
Decontaminate & debride (lavage ± surgical debridement ± dressings)
When should further investigation or surgical exploration be considered for bites and traumatic wounds in small animals?
If wound is located over abdomen or thorax, imaging &/or surgical exploration may be required
When are systemic antibiotics indicated in small animals with bites or traumatic wounds?
If animal is systemically unwell, pyrexic, or if cavity penetration is suspected
Recommended antibiotics:
Cefuroxime ± cefalexin.
Amoxicillin/clavulanate
How is surface pyoderma treated in small animals
Topical treatment
- 2-4% chlorhexidine or other antiseptic
If not responsive or very severe:
- Fusidic acid +- glucocorticoid (cocci)
- Silver sulphadiazine (rods)
What is the preferred first-line treatment for superficial pyoderma in small animals?
Topical treatment
2–4% chlorhexidine q1–3 days
Review after 2–3 weeks & continue until underlying cause is controlled
When should systemic antibiotics be used for superficial pyoderma in small animals?
If topical therapy fails or infection is severe
Always use systemic antibiotics in combination with topical antiseptics
Treat for 2 weeks, then reassess
Investigate resistance if poor response (via cytology, culture & susceptibility testing)
What systemic antibiotics can be used for superficial pyoderma if topical treatment fails?
Clindamycin (first choice due to narrowest spectrum)
Trimethoprim/sulphonamide
Cefalexin
Amoxicillin/clavulanate
When should culture and sensitivity testing (C&S) be performed in small animals with superficial pyoderma?
If there is a history of MRSP/MRSA
If patient has had prior antibiotic courses
If rods are seen on cytology
When should systemic antibiotics be started for deep pyoderma in small animals?
ONLY if infection is painful OR if there is risk of septicaemia
Always perform culture & susceptibility testing before starting systemic antibiotics
What is the recommended topical treatment for deep pyoderma in small animals?
Concurrent topical treatment with 2–4% chlorhexidine q1–3 days
Topical therapy should always be used alongside systemic antibiotics when indicated
What is the primary approach to treating otitis externa in small animals?
Topical treatment ONLY
Assess tympanic membrane integrity – avoid ototoxic products if ruptured
How is cocci-associated otitis externa treated in small animals?
First-line treatment → Antiseptic ear cleaner + topical steroids
If no response after 7 days, ADD topical antibiotics:
Fusidic acid/framycin.
Florfenicol
How is rod-shaped bacteria-associated otitis externa treated in small animals?
First-line treatment → Antiseptic ear cleaner while awaiting culture results
If culture confirms rods, ADD:
Gentamicin.
Framycetin
What additional steps are needed for Pseudomonas-associated otitis externa in small animals?
ADD TrisEDTA + topical antibiotics to treatment
Continue treatment until cytology is negative & underlying cause is corrected
How are superficial bacterial skin infections treated in horses?
Topical antibacterial (e.g. chlorhexidine, silver sulphadiazine) if possible
Correct underlying cause
How are deep pyodermas/cellulitis treated in horses?
Systemic antibiotics
Ideally base on bacterial C&S testing
TMPS where possible – only licensed oral antibiotic available!
7-10 days for mild-moderate, 3 weeks if severe
How should small, superficial bacterial skin infections be treated in farm animals?
Use topical anti-bacterials/antiseptics
E.g.: Chlorhexidine-based products, tetracycline/thiamphenicol spray
How should large or more severe bacterial skin infections be treated in farm animals?
Use non-critically important systemic antibiotics:
- Penicillin
- Cephalosporins
- Oxytetracycline
Treat for 5 days, then reevaluate
How are abscesses treated in all species except rabbits?
Avoid use of antibiotics initially –> allow to mature & ‘point’– poulticing/hot compresses may help to accelerate
Once mature –> lance, drain & flush
Give NSAIDs as needed
Give appropriate antibiotic if patient systemically unwell, pyrexic or cellulitis present
How are abscesses treated in rabbits?
Rabbit pus caseous so can’t lance & drain
Antibiotic unlikely curative – normally used in conjunction with surgical management
Ideally C&S on section of abscess wall (not pus)
Investigate cause (e.g. dental disease) as needed
How is dermatophytosis treated?
- Identify fungus & any predisposing conditions
- Remove infective fungal spores from coat (topical antifungal rinse/shampoo +/- clip hair) –> reduce environmental contamination
- +/- Systemic therapy
- Clean environment as far as possible
- Monitor response to therapy
NB Also can use fungal vaccines for cattle for prevention
Name some topical antifungal shampoos/rinses
Miconazole
- Licensed (in combination with chlorhexidine) as adjunctive treatment for dermatophytosis in cat (Malaseb shampoo)
- Licensed for dogs for bacterial pyoderma
Enilconazole (Imaverol) rinse
- Licensed for cattle, horses, dogs
Human fungal creams (e.g. clotrimazole) occasionally used for local adjunctive treatment, where wash inappropriate (e.g. near eyes) –unlicensed
What are some systemic antifungals?
Itraconazole
- Licensed for cats
- Oral liquid given daily on alternate weeks
- Sometimes used in ‘small furries’
Ketoconazole
- Licensed for dogs – daily oral tablet
- Never for cats
What are the main side effects of itraconazole and ketoconazole (systemic antifungals)?
GI upset & hepatotoxicity (esp. ketoconazole)
Ketoconazole requires hepatic parameter monitoring
Not for animals with liver failure
Ketoconazole may temporarily affect male fertility
What are the treatment options for Malassezia infections?
Topical antifungals
- Shampoos, foams, wipes, ear preparations
- e.g. Miconazole, clotrimazole, posaconazole, nystatin, terbinafine
- Chlorhexidine 2–4%
Systemic antifungals (used in some cases, but often unlicensed)
- e.g. Ketoconazole (dogs, not cats), Itraconazole
When should fungal culture and susceptibility testing be considered in veterinary dermatology?
Subcutaneous (deep) & systemic mycoses
What is the multimodal therapy for atopic dermatitis?
- Control of inflammation & pruritus
- Allergen avoidance & allergen-specific immunotherapy (ASIT)
- Improving skin barrier
- Control of flare factors
What are the advantages and disadvantages of using glucocorticoids to control inflammation & pruritus in atopic dermatitis?
Advantages: Rapid, cheap, strong anti-inflammatory action
Disadvantages: Significant side effects with long-term use
Give examples of glucocorticoids that can be used to control inflammation & pruritus in atopic dermatitis?
Prednisolone
- Oral for dogs, cats, horses
- Dexamethasone (IV/IM) horses
- Use at anti-inflammatory dose then taper to lowest effective q48h dose
Oclacitinib (Apoquel)
- Oral dogs
- Blocks JAK-1 pathway
- Good antipuritic
- Safe long term
Lokivetmab (Cytopoint)
- Monthly injection dogs only
- Monoclonal antibody against IL-31 (targeted therapy = good safety profile)
Ciclosporin
- Oral for dogs & cats
- Potent but onset of action too slow for acute flare
- Expensive
How can allergens be identified in atopic dermatitis cases?
Intradermal testing or IgE serology
Describe allergen-specific immunotherapy (ASIT) for atopic dermatitis cases.
Administer small amounts of relevant allergen to try to induce tolerance
Only option that addresses underlying cause
If effective (70% of cases - takes 12m to assess), long term treatment usually required
Name three ways to improve the skin barrier in atopic dermatitis.
Topical moisturisers (e.g. colloidal oatmeal, aloe vera)
Essential fatty acids (oral/topical)
Essential oils
What are some common flare factors that should be controlled in atopic dermatitis?
Microbial populations (antimicrobial shampoos/wipes)
Ectoparasites
Environmental factors (avoid overheating)
What are the aspects of therapy for autoimmune disease?
- Induction
- Titration
- Maintenance
- Monitoring
What is the goal of induction therapy for autoimmune skin disease, and what drugs are used?
Goal: Rapid lesion control.
Drugs:
- Systemic treatment with GCCs at immunosuppressive doses
- Prednisolone (dogs/cats), Dexamethasone or Prednisolone (horses)
Continue induction treatment until:
- Most lesions healed
- No new lesions for 2 weeks
If no response after 10 days, add adjunctive therapy
Why is a slow taper required in titration therapy, and what adjunctive drugs can be used?
Slow taper reduces relapse risk & side effects
However as lesions often recur as GCC dose reduces, adjunctive treatments are added to help maintain clinical control.
Common adjuncts:
- Azathioprine (not for cats)
- Chlorambucil
- Mycophenolate mofetil
- Ciclosporin (for T-cell-mediated diseases)
- Oclacitinib (emerging evidence)
What is the goal of maintenance therapy, and how is prednisolone tapered?
Goal: Maintain remission with minimal side effects
Tapering:
- Taper until clinical signs just recur to establish lowest effective dose regime, then increase dose to regain control & taper back to lowest effective dose for maintenance
- Reduce prednisolone to alternate-day therapy if possible. Many cases require lifelong treatment
What aspects should be monitored in autoimmune skin disease therapy?
Lesion control, side effects of drugs, blood tests (monitor for hepatotoxicity, bone marrow suppression in azathioprine use)
What are some alternative treatments for autoimmune skin disease?
For localised lesions: Topical GCCs, Tacrolimus
Other options: Pentoxifylline (vasculitis), Oclacitinib alone (emerging)
