antibiotics classes and use

Question 1

describe penicillins basic chemistry and pharmacokinetics

Answer 1

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

Question 2

list some of penicillins species considerations

Answer 2

-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.

Question 3

what is beta-lactamse?

Answer 3

a mechanisms of resistance produced by bacteria. can chop up and knock out penicillin G

Question 4

describe approaches to combating beta-lactamase positive bacteria

Answer 4

1.Beta-lactamase inhibitors - use of 2nd beta-lactam that will irreversibly bind to the 2.beta-lactamase - used as a beta-lactamse inhibitor

Question 5

What are the two beta-lactam antibiotics used

Answer 5

1. Penicillins 2. Cephalosporins

Question 6

list the there classes of beta-lactam penicillin antibiotics and some examples

Answer 6

1. 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.

Question 7

Describe Staphylococcus aureus (“Golden Staph”) historical resistance to Penicillin G

Answer 7

1940- 100% susceptible 1944- 1st beta-lactamase strains appear 1967- 1st methicillian resistant S.aureus (MRSA) 1993- MRSA widely distributed

Question 8

do beta-lactams have a high toxicity? why or why not.

Answer 8

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)

Question 9

what is the most commonly dispensed antibiotic in humans and small animals?

Answer 9

amoxycillin- clavulanic acid

Question 10

list some considerations with clavulanic acid and if it is still affective in the presence of beta-lactamse

Answer 10

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.

Question 11

Describe Procaine Penicillin and list some considerations of it.

Answer 11

• 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

Question 12

Describe the difference between Procaine Penicillin and Benzathine Penicillin

Answer 12

Procaine– used as insoluble salt Bensathine – highly insoluble salt. very long DOA (up to three days, but will often skip below MICs

Question 13

True or False it is ok to give Clavulox to a small herbivore

Answer 13

False, they will die, the clavulox will destroy normal gut flora, clostridium difficile will overgrow and toxin will be produced.

Question 14

Describe Aminoglycosides MOA

Answer 14

1. 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.

Question 15

list the useful members of the Aminoglycosides drug class and specific indications of their uses

Answer 15

-amikacin -gentamicin -kanamycin -neomycin -streptomycin -tobramycin

Question 16

describe Aminoglycosides pharmacokinetics

Answer 16

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.

Question 17

explain how pharmacokinetics influences the use of Aminoglycosides

Answer 17

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.

Question 18

Describe Aminoglycosides and indicate which animal(s) they are used extensively in

Answer 18

Horses. - Kills mostly gram negative - 9 month WHP - dosent kill anaerobes (penicillin used) - dose-dependent - bactericidal - poor oral absorption - vestibular ototoxicity - nephrotoxicity

Question 19

Describe Fluoroquinolones Pharmacokinetics

Answer 19

• 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.

Question 20

Describe how pharmacokinetics influences the chemical use of Fluoroquinolones

Answer 20

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.

Question 21

Explain Fluoroquinolones prevalence of resistance

Answer 21

• development of resistance to in human bacteria

Question 22

explain how Fluoroquinolones toxicity can be minimised

Answer 22

absorption significantly reduced if given orally along with antacids or sucralfate.

Question 23

describe human concerns with the extensive use of Fluoroquinolones in production animals

Answer 23

• 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.

Question 24

•List the pathological processes and specific diseases where oxytetracycline antibiotics are indicated

Answer 24

• rickettsial diseases e.g. spotted fever in humans - Mycoplasma pneumonia - chlamydial infections - psittacosis in birds - borreliosis

Question 25

•List the pathological processes and specific diseases where tyrosine antibiotics are indicated

Answer 25

Has a wide spectrum of activity against gram-positive bacteria, including staphylococci, streptococci, corynebacteria and erysipelothrix

low gram negative spectrum, shown to be active against campylobacter coli and certain spirochaetes.

play a major role in the treatment of bovine pneumonia due to tyrosines active metabolite

Diseases; H.influeza, S.pneumoniae, M.cattarhalis, M.pneumoniae, S.pneumoniae, Legionella spp.

Question 26

describe tylosin MOA

Answer 26

• Bind irreversibly to a site on the 50S subunit of the bacterial ribosome and inhibit the translocation steps of protein synthesis . - May also interfere at other steps, such as transpeptidation. - Generally considered to be bacteriostatic but can be bactericidal at higher doses.

Question 27

•Discuss the PK, PD behind tylosin indications

Answer 27

PK

• IV T half life has shown to be 0.52h
• whilst orally, t half-life was up to 2h.
• therefore this drug should be given orally not IV
• poor water disolvability
• undergo extensive biotransofrmation in the liver
• Under normal conditions, the major route of elimination is the liver. Renal elimination also takes place but it contributes to total clearance only to a small degree, as evidenced by low renal clearance values

PD

• effective agaisnt major respratory tract pathogens
• to be affective the MIC of the organism must be exceeded for atelast 50% of the dosage interval.

Question 28

•Discuss the PK, PD or practical considerations behind oxytetracycline indications

Answer 28

readily chelated by mineral ions with divalent cations such as Ca and Mg. - good absorption form IM - hydrophilic - do not achieve sigfig concentrations in the CNS or penetrate mammalian cells to reach intracellular pathologic organisms. - excreted through kidneys by filtration and to a lesser extent the liver.

Question 29

Explain the risk of tilmicosin toxicity to operator

Answer 29

72h activity against pasteurella after a single injection - injection into humans may be fatal!

Question 30

•List the limitations, contraindications and side-effects of tylosin

Answer 30

• should be avioded in animals with a known hypersensitivity to the product
• oral admin can results in diarrhoea and GIT disturbance, particulary in horses and can be fatal
• injectable formulations can cause pain, inflammation and itchiness
• poor against gram negative organisms therefore shouldnt be used to treat infections of unknown organisms.
• may increase digitalis blood levels and therefore its toxicity.

Question 31

explain Species application of tylosin

Answer 31

Beef Cattle, Dairy Cattle, Swine

WHP, Beef Cattle discontinue use 21 days before slaughter, swine discontinue 14 days before slaughter, do not use in lactating dairy cattle. Do not use in calves being processed for veal.

Question 32

in the diagram below which part is the betlactamas ring?

Answer 32