Antibacterial Drugs in Veterinary Dermatology Flashcards
how common is bacterial pyoderma in the dog? cat?
- Bacterial pyoderma is one of the most frequently encountered skin diseases in the dog
- second most common presenting dermatological complaint (the first is “not determined”!)
- Other than abscesses, it is a much less common reason for presentation in the cat.
what is a recurrent pyoderma?
Recurrent pyodermas appear to resolve with treatment only to relapse when the treatment is completed
- recurrent when relapse is within 1-2 months of apparent clinical cure, or if relapse is on a seasonal basis
What are the causes of recurrent pyoderma?
- Underlying causes leading to deficiencies in the defence mechanisms of the skin – endocrine, cutaneous, metabolic or immunologic abnormality are the classic examples.
- Immunodeficiency syndromes are quite rare.
- how common is allergic dermatitis as an underlying condition for pyoderma?
- what bacteria preferentially colonize? why? when do they produce toxins?
- allergenic dermatitis underlying etiology of 67% of pyoderma cases
- atopic dermatitis creates an opportunity for Staph, esp. S. pseudointermedius to create a biofilm
> Staph increased adherence to corneocytes
> also staph particularly benefit from decreased barrier lipid function in atopic dermatitis - once ‘quorum sensing’ population reached, bacteria switch from proliferatin to toxin production, further reducing barrier dunction of the colonized skin
Pharmacological considerations of a poor response to the treatment for pyoderma could include:
- failure to treat underlying cause
- dose (consider the concept of mutant prevention concentration)
- duration
> The surface heals more rapidly than the deeper tissues. Treat for 1-2 weeks
past the point where lesions can no longer be palpated - frequency
> Antibiotic properties must be kept in mind. Some drugs are concentration
dependant; typically, they are once daily treatment while other drugs are time dependant and are typically used more frequently
what part of the bacterium do beta-lactams target?
Cell wall
what antibiotics attack bacterial ribosomes?
- clindamycin
- chloramphenicol
- tetracycline
- aminoglycosides
which antibiotics attack the folic acid synthesis pathway
potentiated sulfonamides
which antibiotics attack bacterial DNA
fluoroquinolone
which anitbiotics attack bacterial rna
rifampin
Amoxicillin Clavulanate
- what category of antibiotics?
- toxicity
- dose
- beta-lactam
<><>
Toxicity: - adverse GI effects
- hypersensitivities (not dose dependent, cutaneous adverse reaction, fever)
<><>
Dose: - Most dermatologists dose this drug at approximately 20 mg per kg (based on amoxicillin)
cephalexin
- category of drug
- toxicity
- beta-lactam
<><>
Toxicity: - GI adverse effects
- hypersensitivities
cefpodoxime
- type of drug
- dose
- beta-lactam
- 5-10 mg/kg q24h PO
> Once daily
> (I usually try to dose cefpodoxime closer to the 10 mg/Kg dose) - 3rd generation
Cefovecin
- type of drug
- dose, timing
Beta lactam, Cephalosporin
- long-acting (non-depot)
- 3rd generation
- Cefovecin is licensed to last 56 days after reconstitution. Colour change will occur during that time and is not reflective of drug activity/safety
what beta lactam drugs are commonly used in veterinary dermatology? which are first, second, thirds line, and last resort?
ALL FIRST LINE:
- amoxicillin-clavulanate
- cephalexin
- cefpodoxime
- cefovecin
what non-beta lactam antibiotics are used in veterinary dermatology? which are first, second, thirds line, and last resort?
FIRST LINE:
- clindamycin
- Tetracycline, Doxycycline, Minocycline
- potentiated sulfonamides
<><>
SECOND LINE:
- chloramphenicol
- rifampin
<><>
THIRD LINE:
- fluoroquinolones
<><>
LAST RESORT:
- amikacin (aminoglycoside)
clindamycin
- toxicity
- distribution
- rare GI adverse effects
- esophogeal stricture in cats (from capsules administered wihtout food or water in a bolus)
> incompletely dissolved capsule can cause hydrochloride prolonged contact with the esophogeal mucosa due to slow transit time
<><> - plasma protein binding is extensive (>90%)
- widely distributed into most interstitial spaces and even intracellularly (neutrophils and macrophages) due to affinity for lipids
- highest concentrations found in vascular organs
Tetracycline, Doxycycline, Minocycline
- toxicity
- rare GI adverse effects
- esophogeal stricture in cats (from capsules administered wihtout food or water in a bolus)
> incompletely dissolved capsule can cause hydrochloride prolonged contact with the esophogeal mucosa due to slow transit time - doxycycline has little affinity for calcium and does not cause the dental enamel discolouration seen with other tetracyclines in young animals
what antibiotic should not be given with dairy products
tetracycline (doxycycline less affected)
what can the tetracycline niacinamide combination be used for?
what is the contribution of tetracycline? niacinamide?
The combination of tetracycline and niacinamide (NOT Niacin) is a gentle immunomodulatory treatment that can be used for some immune mediated diseases
<><>
o Tetracycline
inhibits neutrophil chemotaxis, degranulation and phagocytosis
inhibits lymphocyte transformation and proliferation
has antioxidant, anti-apoptotic and anti-inflammatory effect
<><>
o Niacinamide
Stabilizes leukocytes from releasing proteases
Protects mast cells from activation and from releasing anaphylotoxins, thus
preventing release of eosinophil and neutrophil chemotactic factors
Blocks IgE mediated mast cell degranulation
Photoprotective
potentiated sulfonamides toxicity
- occasional GI adverse effects
- hypersensitivities
- keratoconjunctivitis sicca (irreversible destructional of lacrimal glands)
- polyarthritis (doberman)
- hemolytic anemia, neutropenia, thrombocytopenia
- hypothyroidism
chloramphenicol toxicity
- prolonged use may cause bone marrow suppression
- reversible dose and time-dependent anemia (dogs>cats) > neutropenia
> monitor CBC q2-4w if treatment exceeds 2 weeks - hind end weakness
<><> - NO irreversible aplastic anemia is in dogs and cats (possible in humans)
fluoroquinolones
- commonly used types, dose
- dog vs human drug
- toxicity
- distribution
Enrofloxacin: 5-20mg/kg
Pradofloxacin: dog: 3.0-4.5 Mg/Kg SID; cat 7.5 mg/Kg OF LIQUID (tabs not same)
<><>
(Cipro = human): Poor Bioavailability of Cipro in dogs
<><>
Distribution: penetrates into all canine tissues and body fluids
<><><>
- rare GI adverse effects
- ocular toxicity in cats (mydriasis, retinal degeneration, loss of vision) > not in prado
- musculoskeletal toxicity in immature dogs (<8 months old in small and medium breeds, <18 months in large and giant breeds, articular cartilage damage)
- Use cation in patients with CNS disorders or kidney disease
- Drug interactions eg. theophyline
what is pradofloxacin, pros
third-generation fluoroquinolone product that is available in a liquid formulation for cats that is marketed as having an “ion technology taste masking.”
- no adverse retinal effects
Fluoroquinolone Safety in Dogs
- contraindications and cautions
Contraindications:
Growing dogs
Pre-existing cartilage diseases
Theophylline co-administration
<><><>
Cautions:
- Use caution in patients with CNS disorders
- Identify underlying concerns
- limit exposure to sun
- Use with caution in kidney patients
- not evaluated in breeding / pregnant / lactating dogs
retinal safety evaluations for pradofloxacin in cats
- specific ocular safety studies with 30 and 50 mg/kg pradofloxacin
- No adverse retinal events were observed with Pradofloxacin
Marbofloxacin retinal safety in cats?
Label:
- fluoroquinolone use has been reported to adversely affect the retina in cats, and such products should be used with caution
<><>
Plumbs:
- although unlikely to occur, the FDA Adverse Drug Reaction database has received some reports of blindness associated with marbofloxacin. Unlike enrofloxacin, causal effect of ocular toxicity has not yet been proven with marbofloxacin, but higher dosages should be used carefully
streptococcus canus necrotizing fasciitis connection to which fluoroquinolones?
- can be seen with enrofloxacin, does not appear to be a problem with marbofloxacin
what tier of drug are fluoroquinolones for bacterial folliculitis?
second tier
aminoglycosides
- esp which drug
- absorption
- toxicity
Amikacin
<><>
Absorption:
- poor absorption for the digestive tract, hence the injectable route. Bioavailability is >90% following IM administration
<><>
Toxicity:
aminoglycoside-induced acute kidney injury (AKI, tubular nephrotoxicity)
- Ototoxicity > cochlear hair cells of the inner ear are susceptible to the toxic effects of aminoglycosides, especially cats
<><>
**Neomycin is found in several topical therapies. Neomycin is a common cause of contact dermatitis
rifampin
- toxicity
- liver injury (hepatotoxicity most common
> 27% of dogs develop increase in liver enzymes
> monitor liver enzymes and CBC q1wk
<><> - rifimpicin-related fatality ~2%
- adverse effects in 16%, most commonly GI and hepatotoxicosis
