Therapeutics: Equine and Farm Animal Flashcards
Name all 10 classes of antimicrobials
- Beta-lactams- penicillin
- Cephalosporins
- Aminoglycosides
- Chloramphenicol
- Pot. sulponamides
- Tetracyclines
- Fluoroquinolones
- Macrolides
- Rifampin
- Metronidazole
Why are beta-lactams commonly used?
What is their MOA?
What is their indications?
Describe their pharmacokinetics and adverse effects
Safety, efficacy and low cost
MOA- interfere with bacterial cell wall production- cell lysis
Indications-
Gram +ve, Strep in horses, anaerobic infections
Syngergisitc with aminoglycosides, additive to fluoroquinolones
Pharma-
Na and K penicillin- IV, Procaine- IM, oral
Elimination mainly kidney
AE- immune reactions (anaphylaxis, haemolytic anaemia, thrombocytopenia), Procaine to CNS if IV or hot
What are cephalosporins MOA?
How are they divided?
What is their pharmacokinetics and adverse effects?
MOA- same as penicillins but more resistant to bacterial defences
Divided into generations- varying efficacty on gram +/-ve, 4th very broad on both
Pharma- rapid absorpbtion, excreted unchanged in urine
AE- same as penicillins
What are aminoglycosides MOA?
When are they indicated?
What is their pharmacokinetics and AE?
MOA- penetrate bacteria, bind to 30s ribosome, cause misreading of genes, bactericidal- Concentration dependent
Indications- Gram -ve infections, pseudomonas
e.g- gentamycin, amikacin, neomycin, streptomycin, tobramycin
Pharma- Poor oral, good other routes, eliminated in glomeruli
AE-
Nephrotoxicity- avoid with other nephrotoxic drugs, enters tubules and uptaken, accumulates in lysosome- rupture cell damage
Monitor- creatinine/ GGT
Endotoxaemia
Ototoxicity- ear
Neuromuscular blockade
What is the MOA of chloramphenicol?
When is it indicated and forbidden?
What are its pharmacokinetics and AE?
MOA- binds to 50s ribosomes and inhibits proteins synthesis- bacteriostatic
Indications- broad spectrum- chlorampenicol/florphenicol
Forbidden in food animals
Pharma- v short half life IV, painful IM, increased absorption orally
AE- not with penicillin, aminoglycosides, fluoroquinolones, macrolides. Colitis
What are potentiated sulphonamides combinations of?
What are their MOA?
When are they indicated?
Pharmacokinetics?
AE?
Combinations of sulphonamide and diaminopyrimidine
MOA- inhibit folic acid pathway, block bacterial nucleic acid synthesis, ineffective in pus and necrotic tissue (increased PABA)
Indications- broad spectrum: strep, staph, some gram-ve (E.coli, salmonella)
Pharma- good oral, liver metabolism, renal excretion
Adverse- agranulocytosis, anaemia, thrombocytopenia, crystalluria, diarrhoea, rapid IV causes collapse
Dines- norodine, detomidine
Name three tetracyclines
What is their MOA?
Indications?
Pharma?
AE?
What can they be used for in foals?
Tetracycline, oxytetracycline, doxytetracyline
MOA- binds to 30s ribosome, inhibit protein synthesis, bacteriostatic
Indications- broad spec- gram + some anaerobes- chlamydia, mycoplasma, ehrlichia
Doxyclcine inhibits MMPs- affects eyes IMMK
Pharma-very lipid soluble, excreted unchanged in urine
AE- fatal colitis, rapid IV causes collapse and death, discolouration of teeth
Engemycin
Name three fluoroquinolones
MOA?
Indications?
Pharmaco?
AE?
Enrofloxacin, marbofloxacin, ciprofloxacin
MOA- inhibit bacterial DNA gyrase, abnormal configuration of DNA, autolysis, bactericidal- optimal activity
Indications- broad spec- most aeobic gram-, some +, mycoplasma, chlamydia, rickettsia
Very effective against enteris gram- (Salmonella), ineffective against anaerobic bacteria
Pharma- good oral absorption, lipid soluble, good distribution, excreted unchanged in urine
AE- cartilage lesions, antagonistic to antimicrobials that inhibit protein synthesis
Name some macrolides
MOA?
Indications?
Pharma?
AE?
Erythromycin, clarithromycin, azithomycin, clindamycin, lincomycin
MOA- binds to 50s ribosomal unit, inhibits protein synthesis, bacteriostatic, quick resistance
Indications- causes colitis in adult horses, rhodococcus equi in foals
Pharma- orally, good penetration, liver metabolism- entero-hepatic circulation- diarrhoea
AE- diarrhoea in adults, hyperthermia
What is the MOA of rifampins?
Indications?
Pharmaco?
AE?
MOA- inhibits bacterial RNA polymerase, decreased RNA synthesis
Indications- staph, rhodoccocus equi, mycobacteria
Pharmacokinetics- 40-70% oral bioavalability, lipophilic, liver metabilism, excreted in bile/urine
AE- Stains everything red- urine, faeces, tears, saliva
Rifampins- RED
What is the MOA of Metronidazoles?
Indications?
Pharma?
AE?
Why rectally given?
MOA- anaerobic bacteria take up and break into small free radicals causing DNA damage
Indications- anaerobic bacteria, protozoa
Pharma- good absorption, lipophilic, hepatic metabolism
AE- mutagenic, neurotoxicity, depression and decreases appetite
Doesn’t taste nice
What are the current concerns about antibiotics?
Fluoroquinolone
Extended spectrum- beta-lactamases
Colistin resistance
Possible to transfer resistance genes
How are sales of antibiotics changing?
Decreasing
Based on dose rate mg/k
resistance depends on dose, confusing for containers
How do the EU classify antibiotics?
Category A-D
A- not licensed for food producing animals- may be in companion animals- ‘Avoid’
B- ‘restrict’
C- ‘caution’ may result in mutation that reduces efficacy of A and B
D- ‘prudence’
What is the cascade?
Describe the sequence for choice of drug
When no authorised product exists for a condition affecting non-food producing species, in order to mitigate suffereing treat with the following sequence:
- Vet med authorised for use in another species, or for a different conditions in the same species
- No product- either- medicine for human use or in accordance with a import certificate a medicine authorised in another state
- In not above- a medicine made up at the time on a one off bases by veterinary surgeon
How is the cascade different for food producing animals?
- Restricted to single holding
- Medicine imported must be authorised for FPA in another state
- Active substance must be in table 1
- Vet specify appropriate withdrawal period
- Vet must keep specific records
- If there is authorised product- should be used
- May judge there is no authorised product- resistance
- Dosage and characteristics taken into account
- Chronic infections- failure or authorised
- Build up of resistance- rotation of authorised and cascaded product
- Complex conditions- drug compatability
- Product unavailable- diligent search
How should prescribing be approached?
What is wrong- idenfitgy targets for therapy
Use critically reviewed infro
Appreciate supporting and curing condition
What therapies available- licensed, cascade
Comment on alternatives- euthanasia, surgery
Cost
Be aware of risks- animal, clients, staff
Prevention- education
What needs to be considered with treatment choice?
For example give every cow with mastitis synulox
One possible and expensive treatment, no diagnosis needed- could return though
Best long term is prevention which requires accurate diagnosis
Could be given other drugs to help- oxytocin to flush out bacteria
List categories of antibiotics based of the following MOA:
- Disrupt cell wall production
- DNA action inhibitors
- Protein synthesis inhibitors
- Cell membrane function
- B-lactams, penicillins, cephalosporins
- Potentiated sulphonamides, fluoroquinolones
- Streptomycin, tetracycline, macrolides, florphenicol
- Monensin
What considerations should be kept when prescribing antibiotics?
Some diseases have a high self-cure rate
Local resistance can vary a lot
Should antibiotic be left on the farm for future cases
Spectrum- broad (more successful) or narrow (better for resistance)
Does it enter correct tissue/serum
What causes antibiotics to enter tissue or serums? and name examples
Acidic antibiotics enter serum- penicillin, amoxycillin, clavulanic acid, cephalosporin
Alkaline anter tissue- macrolides
Some neutral equal in both- oxytetracyline/sulphonamides
Remember inflammation changes barrier so will affect concentrations in tissues
How long do antimicrobials need to be present for?
MOA dependent
Time over minimum inhibitory concentration (MIC)- penicillins, cephalosporins, tetracyclines, macrolides
Concentration dependent- aminoglycosides
Area under the curve dependent- fluoroquinolones
What is synergism?
Potentiation of one drug action by another
Concnetration dependent
Phase of bacterial life cycle when active- growth/biofilms
Possible antagonism if concentrations wrong
How should antibiotics be dosed?
Dose needs to be well over the MIC at least once daily- depends on half life
Can be dictated by formulation
What affects withdrawal period?
How can drugs sush as excenel have short/no withdawals but a 24h dose interval?
Soluble- oil based not
pH
Organism sensitivity
Human toxicity
Soluble drug therefore no injection site residue
Acidic so doesnt enter the milk
Organisms are highly sensitive- low MIC- therefore below human toxicity dosage
What NSAIDs are currently available for cattle?
Flunixin meglamine- Finadyne
Ketoprofen- ketofen
Telenamic acid- Tolfine
Meloxicam- metacam
Carprofen- Rimadyl
Aspirin- Solacyl
