Therapeutics Flashcards
what are common groups of antimicrobials used in equine medicine?
beta-lactams cephalosporins aminoglycosides chloramphenicol potentiated sulphonamides tetracyclines fluroquinolones macrolides rifampin metronidazoles
why are beta-lactams commonly used?
safety, efficacy and low cost
what is the mechanism of action of beta-lactams?
interfere with bacterial cell wall production causing cell lysis
what are the indications for beta-lactams?
gram positive bacteria
Streptococcal infections (horses)
most anaerobic infections
what indication do beta-lactams have limited efficacy in?
abcesses
what drugs do beta-lactams have a synergistic effect with?
aminoglycosides
what drugs do beta-lactams have an additive effect with?
fluoroquinolone
what is the main way beta-lactams are eliminated from the body?
via kidney
what are the two types of beta-lactam penicillins?
Na and K (IV)
procaine (IM)
what are the adverse effects of beta-lactams?
anaphylaxis (type I hypersensitivity)
haemolytic anaemia
thrombocytopenia
what is the mechanism of action of cephalosporins?
interfere with bacterial cell wall production causing lysis (more resistant to bacterial defences than beta-lactams)
how and where are cephalosporins excreted?
unchanged in urine
what are the adverse effects of cephalosporins?
anaphylaxis (type I hypersensitivity)
haemolytic anaemia
thrombocytopenia
why should cephalosporins never be used as a first line drug?
they are critically protected
what is the mechanism of action of aminoglycosides?
penetrate bacteria and bind to 30S ribosomal subunit leading to misreading of genetic codes
do aminoglycosides work best in gram positive or negative bacteria?
negative - only these have the ability to get the drugs inside of them
are aminoglycosides bacteriocidal or bacteriostatic?
bacteriocidal
how are aminoglycosides removed from the body?
glomerular filtration (kidneys)
what are the adverse effects of aminoglycosides?
nephrotoxicity
endotoxaemia
ototoxicity
neuromuscular blockade
what is the mechanism of action of chloramphenicol?
binds to 50S ribosomal subunit to inhibit protein synthesis
is chloramphenicol bacteriostatic or bacteriocidal?
bacteriostatic
what animal can chloramphenicol not be used in?
food producing animals
where are chloramphenicols metabolised and excreted?
metabolised in liver
excreted renally
why are chloramphenicols not commonly used?
painful IM injection
expensive
what drugs should chloramphenicol not be used with? and why?
penicillin, aminoglycosides, fluoroquinolnes, macrocodes
shouldn’t mix bacteriostatic and bacteriocidal drugs
what is the mechanism of action of potentiated sulphonamides?
inhibit folic acid pathway to block bacterial nucleic acid synthesis
why are potentiated sulphonamides very safe to use in mammals?
mammals don’t create their own folic acid so will have no effect
when are potentiated sulphonamides ineffective?
anaerobes
in pus and necrotic tissue
where are potentiated sulphonamides metabolised and excreted?
liver metabolism
renal excretion
what are the adverse effects of potentiated sulphonamides?
agranulocytosis, anaemia, thrombocytopenia
diarrhoea
crystalluria
what is the mechanism of action of tetracyclines?
binds to 30S ribosomal subunit to inhibit protein synthesis
is tetracycline bacteriocidal or bacteriostatic?
bacteriostatic
why are tetracycline very safe to use in mammalian species?
mammalian cells cannot transport the drug into themselves
what are the indication of tetracycline use?
broad spectrum gram positive and negative
contracted tendon in foals
how and where are tetracyclines excreted?
unchanged in urine and bile
what property of tetracyclines means they penetrate cells very well?
very lipid soluble
what are the adverse effects of tetracyclines?
fatal colitis
diarrhoea
teeth discolouration
collapse/death if given rapidly IV
what is the mechanism of action of fluoroquinolones?
inhibits bacterial DNA gyrase leading to incomplete configuration of DNA
are fluoroquinolone bacteriocidal or bacteriostatic?
bacteriocidal
what are the indication of fluoroquinolone use?
broad spectrum (better against gram negative) very effective against gram negative enteric bacteria
how and where are fluroquinolones excreted?
unchanged in the urine
what are the adverse effects of fluoroquinolone?
cartilage lesions (foals)
what types of drugs do fluoroquinolone antagonise?
antimicrobials that inhibit bacterial protein synthesis (chloramphenicol, rifampin)
why should fluoroquinolone never be first line drugs?
they are critically protected
what is the mechanism of action of macrolides?
binds to 50S ribosomal subunit to inhibit protein synthesis
are macrolides bacteriostatic or bacteriocidal?
bacteriostatic
when should macrolides never be used?
adult horses - diarrhoea and death
when is the only time macrolides are used in equine medicine?
foals with Rhodococcus equi
what is the mechanism of action of rifampin?
inhibit bacterial RNA polymerase leading to decrease RNA synthesis
what are the main indications of rifampin use in horses?
staphylococcus
rhodococcus equi
mycobacteria
where is rifampin excreted?
in the bile
what is the main adverse effect of rifampin?
stains everything red - urine, tears, faeces, saliva
what is the mechanism of action of metronidazole?
anaerobic bacteria take it up and break it into small free radicals leading to DNA damage
what are the adverse effects of metronidazole?
mutagenic
neurotoxicity
depression
decreased appetite
what does therapeutics rely upon?
a correct diagnosis (better diagnosis means better treatment)
why do turkeys have a higher amount of antibiotic usage than other poultry?
grown in high concentrations with high risk so are treated if there is any doubt
what are the categories for the new EU antibiotic classification?
A - human critically important (not used in food producing animals)
B - critically important in food producing animals
C - may lead to resistance in category A/B so use cautiously
D
what is the sequence for the cascade for a non-food producing animal?
veterinary medicine authorised for use in another species or for different condition in same species
medicine authorised for human us in UK or product authorised in another state
medicine made up at the time on a one-off basis
what are the rules that apply to the cascade for food producing animals?
restricted use to a single holding
medicine imported must be authorised for food-producing species on other states
active substance must be in Table 1 (regarding maximum residue limits (MRLs))
vet must specify appropriate withdrawal period
what are some points that must be evaluated for prescribing therapeutics?
define what it wrong with the animal identify the targets for therapy critically evaluate the information what therapies are available and how does it work alternatives to therapy cost of treatment what are the risks how is it administered
what are some alternative to prescribing therapeutics?
euthanasia
surgery
what are some ways antibiotics work?
disrupt cell wall production
DNA action inhibitors
protein synthesis inhibitors
effect cell membrane function
what are some examples of antibiotics that disrupt cell wall production?
beta lactams
penicillins
cephalosporins
what are some examples of antibiotics that inhibit DNA action?
potentiated sulphonamide
fluroroquinolones
what are some examples of antibiotics that inhibit protein synthesis?
tetracyclines
macrolides
florphenicol
streptomycin
what is an example of an antibiotic that effects cell membrane function?
monensin
