antibiotics classes and use Flashcards
describe penicillins basic chemistry and pharmacokinetics
Pharmacokinetics: - rapid absorption - t1/2 usually short (under hr) therefore repository salts utilised in parenteral formulations - good distribution except for eye, prostate and non-inflamed CNS
list some of penicillins species considerations
-horses if given orally die, IM ok (as with other larger herbivores) - cannot be given to small herbivores; cecum to small t diffuse out slowly and all of their good bacteria in their digestive tract is killed rapidly - easier with non-fermemnters.
what is beta-lactamse?
a mechanisms of resistance produced by bacteria. can chop up and knock out penicillin G
describe approaches to combating beta-lactamase positive bacteria
1.Beta-lactamase inhibitors - use of 2nd beta-lactam that will irreversibly bind to the 2.beta-lactamase - used as a beta-lactamse inhibitor
What are the two beta-lactam antibiotics used
- Penicillins 2. Cephalosporins
list the there classes of beta-lactam penicillin antibiotics and some examples
- Natural penicillins - narrow spectrum; predominantly gram positives and anaerobes (e.g. staphylococcus) - Penicillin G, benzylpenicillin 2. Aminopenicillins - broader spectrum, as above plus some gram negatives; E-coli and proteus - amoxycillin, ampicillin 3. Others - beta-lactamase stable penicillins, e.g. methicillin, cloxacillin, extended spectrum.
Describe Staphylococcus aureus (“Golden Staph”) historical resistance to Penicillin G
1940- 100% susceptible 1944- 1st beta-lactamase strains appear 1967- 1st methicillian resistant S.aureus (MRSA) 1993- MRSA widely distributed
do beta-lactams have a high toxicity? why or why not.
no. very safe can be sued in geriatrics, juveniles, pregnancy and during lactation. because side effects usually come about through dysbiosis - killing good bacteria, toxins, GIT signs (diarrhoea and vomiting most common)
what is the most commonly dispensed antibiotic in humans and small animals?
amoxycillin- clavulanic acid
list some considerations with clavulanic acid and if it is still affective in the presence of beta-lactamse
yes it is affective in presence of beta-lactamse keep refrigerated, can be given IM and SC NEVER IV label dose is often considered too low.
Describe Procaine Penicillin and list some considerations of it.
- Predominately gram positive coverage - dosent work against beta lactamase producing bacteria - convenient dosing (sid) - keep refrigerated - IM, SC NEVER IV - prescribed commonly without rational reason
Describe the difference between Procaine Penicillin and Benzathine Penicillin
Procaine– used as insoluble salt Bensathine – highly insoluble salt. very long DOA (up to three days, but will often skip below MICs
True or False it is ok to give Clavulox to a small herbivore
False, they will die, the clavulox will destroy normal gut flora, clostridium difficile will overgrow and toxin will be produced.
Describe Aminoglycosides MOA
- Interferes with bacterial protein synthesis o Binds to the 30S ribosomal subunit. o Needs an oxygen-dependent transport 2. Rapidly bactericidal. 3. Concentration-dependent bactericidal o The rate and extent of bacterial killing increases as drug concentrations increase. 4. Post-antibiotic effect o Continued killing of bacteria even though there is too low MIC levels.
list the useful members of the Aminoglycosides drug class and specific indications of their uses
-amikacin -gentamicin -kanamycin -neomycin -streptomycin -tobramycin
describe Aminoglycosides pharmacokinetics
o Poor oral absorption as they are hydrophilic. o Intramuscular absorption is good (Peak blood levels are achieved within 0.5-1.5 hours) o Distribution. Urine, kidney, endolymph, and perilymph of the inner ear. o Penetration into the central nervous system is poor o Elimination. o Glomerular filtration by the kidneys accounts for almost all (99%) of the elimination. Aminoglycosides are removed by peritoneal and hemodialysis. t half-life approx. two hours. cross the placenta readily.
explain how pharmacokinetics influences the use of Aminoglycosides
half life can increase to 30-60 hours in patients that have renal failure therefore dose must be change in these cases. not given orally (absorption poor) high elimination therefore dosage must be given constantly. when administered parenterally it remains mostly in the extracellular fluid therefore volume of distribution is larger in younger animals then older ones of the same size.
Describe Aminoglycosides and indicate which animal(s) they are used extensively in
Horses. - Kills mostly gram negative - 9 month WHP - dosent kill anaerobes (penicillin used) - dose-dependent - bactericidal - poor oral absorption - vestibular ototoxicity - nephrotoxicity
Describe Fluoroquinolones Pharmacokinetics
- highly limpophilic and accumulate in high concentrations in the kidneys, liver, lungs, bone, joint fluid, (aq) humour of the eyeball and respiratory tissues. - often present in concentrations that far exceed MIC of infected organs. - elimination; in the urine in high concentrations.
Describe how pharmacokinetics influences the chemical use of Fluoroquinolones
due to high MIC; often used to treat severe infections of the skin, respiratory tract and urinary tract can accumulate in prostate therefore used for prostate infections.
Explain Fluoroquinolones prevalence of resistance
- development of resistance to in human bacteria
explain how Fluoroquinolones toxicity can be minimised
absorption significantly reduced if given orally along with antacids or sucralfate.
describe human concerns with the extensive use of Fluoroquinolones in production animals
- resistance in human bacteria let to a band of use of these in any food-producing animal. - concern of impact of residuals in human food.
•List the pathological processes and specific diseases where oxytetracycline antibiotics are indicated
- rickettsial diseases e.g. spotted fever in humans - Mycoplasma pneumonia - chlamydial infections - psittacosis in birds - borreliosis
