Drugs = Dermatology

Corticosteroids

Example: Dexapent or Pred-X5

• Method of Action

  • steroidal anti-inflammatory (overdose = immunosuppression)

  • Bind to steroid receptors = alter DNA + gene expression

  • act on multiple metabolic pathways in every cell type

  • dose-dependant effects

• Indications

  • allergic dermatitis = atopy, fleas, contact or food allergy

  • neoplasia = mast cell tumour, lymphoma

  • immune mediated skin disease = pemphigus, discoid lupus

• Benefits

  • potent = fast acting and broad spectrum

• Contraindications

  • systemic fungal infections

  • NSAID

  • be cautious if: active bacterial infections, diabetes, young animals, not vaccinated

• Adverse Effects

  • PU/PD

  • polyphagia (hungry)

  • muscle catabolism and thinning of skin

  • pot belly

  • panting

  • GI effect - ulcers, vomiting, diarrhoea

  • immunosuppression

  • increased liver enzymes

• Client Info:

  • must wean off drug as patient is at risk of hypoadrenocorticism

  • side effects with long term use

Oclacitinib

Example: Apoquel

• Method of Action: Janus kinase inhibitor = blocks inflammatory cytokines (IL-31)

• Indications:

  • allergic dermatitis - atopy, food allergy, flea

  • good for epitheliotropic lymphoma

  • off label for cats

• Benefits: fast acting and low side effects

• Contraindications: immunosuppressive, don’t use if <1year old

• Adverse effects:

  • GI effect - vomiting, diarrhoea, inappetence

  • immunosuppression may lead to secondary infections

• Client Info:

  • monitor for symptoms of skin and respiratory infections

  • x2 per day for x2 weeks, then x1 per day ongoing

  • expensive

Lokivetmab

Example: Cytopoint

• Method of Action:

  • caninized monoclonal antibody that binds + neutralises IL-31

  • only works in dogs, no effect in cats

• Indications: allergic dermatitis - atopy, food allergies

• Benefits

  • prolonged effect = every 4-8 weeks / as needed

  • does not rely on owner compliance

  • safe for any age and high margin of safety

• Contraindications: ineffective in cats

• Adverse Effects:

  • pain on injection

  • GI signs - vomiting

  • lethargy

  • treatment induced immunogenicity (patient develops own antibodies to drug)

• Client Info

  • does not “cure” = need to return for follow up

  • expensive

Cyclosporine

Example: Atopica or Sandimmun Neoral

• Method of Action:

  • blocks transcription genes needed for T cell activation

  • reduces interleukin (IL-2) production = immunosuppression

• Indications:

  • immune mediated skin diseases

• Benefits:

  • immunosuppressive with less profound side effects than prednisolone

  • freezing capsules can reduce possible GI effects

• Contraindications:

  • if history of malignant neoplasia

  • caution if: pregnant, not vaccinated, liver disease, concurrent immunosuppressive medication/illness

• Clint Info: expensive

Immunotherapy

• Method of Action: increases production of T-regulatory cells

• Indications: atopic dermatitis

• Benefits: effective for long periods of time

• Adverse SE: possible allergic reaction

• Disadvantages: may take several months to start working, some patients has no effect

Essential Fatty Acids

Example: Dermega oral supplement

• Method of Action:

  • incorporated into cell membrane → improve epidermal lipid barrier + reduce pri-inflammatory by-products

  • enhanced effect with steroids and antihistamines

• Indications:

  • allergic dermatitis - atopy, food allergy, flea, contact dermatitis

  • keratinisation disorders - dandruff

• Benefits: no prescription needed as minimal side effects

• Contraindications:

  • coagulation disorders

  • be cautious if diabetic, or pancreatitis

• Adverse Effects: GI effects - vomiting, diarrhoea

• Client info:

  • may not see positive effects for 2-3 months

  • monitor for bruising or bleeding

  • can use human version, but better to buy pet-specific version for safe dosing

Antihistamines

• act on histamine receptors (H1) as “inverse agonists”

  • agonist = stabilise receptor in their inactive configuration

• down regulate effects of histamine

• best given before histamine drive inflammation is present

Types of antihistamines:

• First Generation H1 Antihistamines

  • Block muscarinic receptors

  • Act on endothelial cells = reduce vascular permeability, vasodilation, glandular secretions (reduce wheals + lacrimation)

  • Act on central actions (pass blood brain barrier) = sedation

  • Examples = Chlorpheniramine and Diphenhydramine

• Second Generation Antihistamines

  • specific to the H1 receptor so does not pass the blood brain barrier (no sedation)

  • Examples: Loradine, Cetirizine, Fexofenadine (Terfenadine) = human products such as Zertec, Claratyne, Telfast

Note: allergic response is complex due to multiple mediators involved → variable efficacy and little evidence to support H1 receptors antihistamines work. New evidence finds H4 receptors that work on T lymphocytes, neurons + keratinocytes work better

How do you choose an antimicrobial?

• Antimicrobials should be chosen dependent on clinical features + consider antimicrobial stewardship

  • prevent and manage common disease

  • use evidence based approach to choose antimicrobials

  • use antimicrobials sparingly + evaluate outcome

• Antimicrobials can be topical or systemic (first or second line)

• The Australian Infectious Diseases Advisory Panel has endorsed Antibiotic Prescribing Detailed Guidelines (dogs and cats)

Topical vs Systemic Antimicrobials

Topical = mild, surface and or focal infections

Systemic = severe, deep or generalised injections (often alongside a topical)

• depth of infection will effect length of treatment

• systemic + topic can assist in recovery

• most pyoderma (especially in dogs) is secondary to other pathologies → these must be addressed for definitive cure

• Systemic 1st Line = Cephalexin or Amoxicillin / Clavulante

  • used for bacterial infections (staphylococci)

• Systemic 2nd Line = Cindamycin, Enrofloxacin, Marbofloxacin, Cefovecin

  • dependant on culture and sensitivity of results

Systemic Antifungal Drugs

Itraconazole (Sporanox) = used for dermatophytosis (ringworm) → treat until cured, 6-10 weeks

Terbinafine = used for used for dermatophytosis (ringworm) → limited data

Fluconazole = used for superficial Malassezia infections (yeast) → limited data

Bactroban

Topical skin preparation

Active ingredient = 2% mupriocin (antibiotic)

• bactericidal on most Gram +ve cocci

Uses = superficial bacterial pyoderma

Directions = apply x2 daily until healed

Flamazine

Topical Skin Preparation

Active ingredient = 1% silver sulfadiazine (antiseptic)

• bactericidal on Gram +ve and -ve including Pseudomonas and Staphylococcus spp

• broad antifungal against yeast and Asperigullus

Uses = superficial bacterial pyoderma, wounds, burns

Directions = apply 3-5 mm layer x1 per day until healed

Manuka Honey

Topical Skin Preparation

Active ingredient = honey

• broad bactericidal effect due to hydrogen peroxide liberation + phytochemical constituents

• osmotic gradient helps decrease inflammatory oedema

Uses = open wounds

Directions = clean + dry skin, 3mm layer over wound/dressing, replace as required

Fungafite

Topical Skin Preparation

Active ingredient =

• miconazole (antifungal)

• also works against some Gram +ve bacterial

Uses = fugal pyoderma e.g. ringworm

Directions = x1 daily until resolved, up to 6 weeks

Medicated Shampoos

Topical Skin Preparation

Active ingredient = dependant on use

• Pyohex: chlorhexidine (antibiotic)

• Malaseb: chlorhexidine (antibiotic) + miconazole (antifungal)

• Mediderm: piroctone olamine (mild antibacterial + antifungal)

• Barazone: budesonide (steroid)

Uses = superficial and generalised pyoderma

Directions = apply as directed ensuring contact time is adequate

Neocort

Topical Skin Preparation

Active ingredient =

• neomycin (antibiotic)

• hydrocortisone (topical steroid)

• lignocaine (topical anaesthetic)

• bactericidal against a range of bacteria (more Gram -ve) including Staphylococcus

Uses = skin irritation of neomycin-sensitive organisms or need topical anti-inflammatory/anaesthetic effects

• not used for superficial pyoderma or open wounds

Directions = x2 per day for up to 2 weeks

Cortavance

Topical Skin Preparation

Active ingredient = hydrocotisone (steroid)

Uses = inflammatory skin disease, off label for ear canals

• not used for open wounds

Directions = spray from 10cm, x1 per day for 1 week

Otoflush vs Epiotic

Otic ear cleaner - remove debris first for better penetration

Otoflush	Both	Epiotic
Active ingredient polyhexamethylene biguanide (antiseptic) neutral buffered ear cleaner	Active ingredient disodium edetate (chelating and cleansing)	Active ingredient salicylic acid (oil-soluble cleanser) balances pH and break down biofilm + some bacteria
Uses: off label for cats can help if ruptured tympanic membrane	Uses: active infections and ear maintenance Directions = 0.5-1.5mL in ear and massage	Uses: can prevent recurrent yeast infections

Cortavance

Otic ear cleaner - remove debris first for better penetration

Active ingredient: hydrocotisone (steroid)

Uses: off-label in ears but good to prevent infection + recurrent yeast infections

Treatment for Active Otitis Externa

	Dermotic / PMP	Easotic	Aurizon	Osurnia
Active Ingredient	polymyxin B (antibiotic) miconazole (antifungal) prednisolone (steroid)	gentamicin (antibiotic) miconazole (antifungal) hydrocortisone (steroid)	marbofloxacin (antibiotic) clotrimazole (antifungal) dexamethasone (steroid)	florfenicol (antibiotic) terbinafine (antifungal) betamethasone (steroid)
Use	1st line low cost broad spectrum	expensive Good for rod bacteria contraindicated for tympanic membrane rupture	Last line Best for rod bacteria contraindicated for tympanic membrane rupture	expensive forms a gel in the ear must be done in clinic
Directions	fill ear + massage x2 per day for 1 week	1ml + massage x1 daily for 5 days	fill ear + massage x1 per day for 1-2 week	1ml + massage Repeat after 1 week