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DWT Exam 2 > Pharmacology Antimicrobials > Flashcards

Pharmacology Antimicrobials Flashcards

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1
Q

What is the Minimum Inhibitory Concentration (MIC)?

A

The lowest concentration of drug that INHIBITS visible bacterial growth

Ex: MIC90 means the concentration for inhibiting 90% of the bacteria

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2
Q

What does Minimum Bacterial Concentration (MBC) mean?

A

The lowest concentration of a drug that KILLS 99.9% of bacteria

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3
Q

What does bacteriostatic mean?

A

Stops bacteria from multiplying; does not kill them and requires an immune competent patient

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4
Q

What are bacteriostatic drugs not good for?

A

Sepsis
Neonates
Animals on glucocorticoids
Animals on cancer chemotherapy

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5
Q

What does bactericidal mean?

A

Kills bacteria if concentrations reach MBC for a certain period of time

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6
Q

What type of anti microbial drug is best for immunosuppressive animals?

A

Bactericidal antimicrobials

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7
Q

What are bactericidals preferred for?

A

Sepsis
Neonates
Animals on glucocorticoids
Animals on cancer chemoerapy
Severely I’ll patients

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8
Q

What does postantibiotic effect (PAE)mean?

A

Stays in animal after plasma concentrations decline below the MIC/MBC

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9
Q

What are the mechanisms of postantibiotic effect?

A

1) decrease virulence of the bacteria
2) development of abnormal cell wall or septum
3) increased susceptibility to host defenses
4) persistence at sites of infection

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10
Q

Does postantibiotic effect occur in all drugs?

A

No, only some

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11
Q

Is the postantibiotic effect bacteria dependent or independent?

A

Dependent

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12
Q

What is the relationship between pharmacokinetics- pharmacodynamic interactions?

A

Used to predict the success of antimicrobial therapies & to relate concentration of drug to MIC of the pathogen

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13
Q

What are “Drug-Bug” interactions?

A

How long the postantibiotic effect lasts based on the antibiotic & the specific bacteria you are trying to treat

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14
Q

What are Time-Depemdent antibiotics?

A

Duration plasma concentration is above the MIC for over 24 hours

Treatment success is based on how long a 24 hour period the concentration in the plasma are above the MIC of that bacteria

Ex: Beta- lactation antimicrobials

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15
Q

What are Concentration- Depemdent antibiotics?

A

Cmax:MIC

Ratio of the maximum plasma concentration to the MIC

Ex: Aminoglycoside antimicrobials

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16
Q

What are concentration/Time-Depemdent antibiotics?

A

AUC:MIC

Ratio of the AUC from 0 to 24 hours to the MIC

Ex: flueroquenolones

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17
Q

What are the 3 categories of antibiotic mechanism of action?

A

1) Inhibit cell wall synthesis and function
2) Inhibit nucleocapsid acid synthesis and function
3) Inhibit protein synthesis specifically the 50s subunit and the 30s ribosomal subunit

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18
Q

What is the difference between narrow spectrum and broad spectrum antimicrobial?

A

Narrow spectrum antimicrobials implies activity against a limited subset of bacteria while broad spectrum implies activity against a wide range of bacteria

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19
Q

What does spectrum of activity tell you?

A

That a bacteria CAN BE affected by the antimicrobial

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20
Q

True or False: individual isolates of bacteria may be resistant to an antimicrobial even though they are part of the spectrum

A

True

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21
Q

What are the 6 quadrants of the antibacterialspectrum

A

1) aerobic, gram + streptococci
2) aerobic, gram + staphylococci
3) aerobic, gram - respiratory pathogens
4) aerobic, gram - enteric pathogens
5) anaerobic gram +
6) anaerobic gram -

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22
Q

What does additive/indifferent mean when discussing antmicrobial drug interactions?

A

the combination of 2 antimicrobials to extend the spectrum

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23
Q

What is antagonism in relation to antimicrobial drug interactions?

A

the combination of the drugs cancels the effects of both of the drugs equally

Ex: Penicillin + tetracycline

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24
Q

What are the characteristics of intravenous drug route of administration?

A

Used with systemic illness
highest concentration
highest risk for adverse effects

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25
What are the characteristics of IM/SQ drug route of administration?
Bioavailability often complete risk of drug toxicity is less than IV Dehydration/shock will affect absorption
26
Why is the oral route contraindicated?
Can cause ileus/colitis Malabsoprtion drug interactions
27
what are the main reasons why we choose an antibiotic?
Availability Ease of use Adverse effects Cost Species being treated
28
What drug classes do beta-lactam antibiotics include?
Penicillins Cephalosporins Carbapenema Monobactams
29
What is the mechanism of action for beta-lactams?
Penetrate the outer cell wall Bind to & inhibit penicillin binding proteins Inhibition of cross-linking Opens channels through the cell wall to create pores which allows fluid into the cell causing swelling & death
30
Are beta-lactose’s bacteriostatic or bactericidal?
Bactericidal
31
What are the pharmacokinetics of Beta-lactams?
Low plasma protein binding Hydrophilic Do not distribute well to protected sites Short half-life (frequent dosing) Some post antibiotic effect against gram + bacteria
32
What are the pharamcokinetics of beta-lactam metabolism and elimination?
Minimal metabolism Elimination through glomerular filtration and tubular secretion
33
Are beta-lactams a good choice for cystitis and if so why?
Yes, because they are eliminated through glomerular filtration & tubular secretion means that there are very high concentrations in the urine
34
What are the 4 different penicillin groups?
Benzylpenicillins Aminopenicillins Extended spectrum penicillins Anti-staphylococcal penicillins
35
What are benzylpenicillins effective against?
Gram positives streptococcus species anaerobes
36
Are Benzylpenicillins effective against gram negative bacteria why or why not?
No because gram negative bacteria are usually resistant
37
What inactivates Benzylpenicillins and why?
Beta-lactamases because it breaks down the beta-lactam ring
38
What is an example of a benzylpenicillin drug?
Penicillin G
39
What are the routes of administration for Penicillin G and their characteristics?
Oral absorption is limited because it degrades in gastric acid IM/SQ complexed with procaine or benzathine which give it a longer half life and can be dosed less frequently
40
Why does benzathine penicillin suck as a drug choice
Never reaches therapeutic concentrations
41
What are the key concepts of Penicillin G?
Effective against streptocci & anaerobes Susceptable to Beta-lactamases Inadvertant IV injection of procain penicillin causes severe procain reactions Benzathine formulations do not reach therapeutic concentrations
42
What are the key concepts of Aminopenicillins?
Effective against streptococci and anaerobes Increasing gram-negative spectrum Susceptible to beta-lactamases unless combined with a BL1 Ex: Amoxicillin + calvulanic acid & ampicillin +sulbactam
43
What are the key concepts of Aminopenicillins?
Effective against streptococci and anaerobes Increasing gram-negative spectrum Susceptible to beta-lactamases unless combined with a BL1 Ex: Amoxicillin + clavulanic acid & ampicillin +sulbactam
44
What is the number one antibiotic chosen for dogs and number two in cats?
Amoxicillin + Clavulanic acid
45
What are Extended spectrum penicillins used for?
Drugs in this class rarely used clinically and NOT on test
46
What are anti-staphylococcal penicillins effective against?
Little activity against gram negative or anaerobic organisms
47
what is the key concept of anti-staphylococcal drugs
bacteria reported resistant to oxacillin should also be considered to be resistant to all other beta-lactam antibiotics
48
What drugs are anti-staphylococcal?
Methicillin Oxacillin
49
What are the classifications of cephalosporins?
1st, 2nd, 3rd, 4th Generations
50
What are the characteristics of 1st generation cephalosporins?
Effective against gram positive bacteria including beta-lactamase positive staphylococci Commonly prescribed in dogs
51
What drugs are in the 1st generation cephalosporins?
Cefazolin Cephalexin
52
What are the characteristics of 2nd generation cephalosporins?
Greater activity against gram-negative bacteria Effective against gram positive bacteria
53
What are the characteristics of 3rd generation cephalosporins?
has the most activity against gram-negative bacteria still retain activity against gram positive but should use 1st gen if treating these Not used clinically if used judiciously
54
What drugs are in the 3rd generation cephalosporins?
Ceftior, cefovecin, cefpodoxime proetil
55
Why should 3rd generation cephalosporins be avoided?
Because they could lead to antibiotic resistance and these drugs are key in human medicine
56
What is cephalexin used for in dogs and cats?
Dermatitis caused by non-methicillin/oxacillin resistant staphylococci
57
What is cefazolin used for in dogs and cats?
IV use Extralable use Surgical prophylaxis administerd 60 min of incision
58
what is cefpodoxime used for in dogs?
skin and soft tissue infections Longer half-life (once daily dose) Prodrug- ester improves oral absorption (proxetil)
59
What is Cefovecin used for?
Treatment of skin infections of dogs & cats single SQ dose has a long half-life due to high affinity protein binding Provides therapeutic concentrations for up to 14 days #2 antibacterial in cats
60
What is ceftior used for?
approved for use in dogs, horses, chickens. turkeys, cattle, goats, sheep and swine Ex: ceftiofur crystalline free acid (Excede)
61
What are the characteristics of ceftiofur crystalline free acid (Excede)?
Long acting (half-life due to extended-release formulation) singe SQ dose at the base of the ear for cattle Single IM dose in swine IM dose in horses repeated every 4 days Injection site reactions are common!
62
What is the one cephalosporin drug that can be used in major food producing species as long as the other label indications are met?
Cephapirin
63
What are the possible adverse effects with beta-lactam antibiotics?
Relatively rare Hypersensitivity reactions Cross-reactivity between penicillins and cephalosproins may exist at high concentrations can inhibit GABA CNS excitement & seizures Procaine reactions GI effects (dogs/cats vomiting) (horses/rabbits colitis)
64
What animal should procain penicillin never be given IV to?
Horse
65
What are the mechanisms of resistance for beta-lactam antibiotics
Methicillin-resistance (MecA gene encodes for penicillin bidning protein and creats very low bidning affinity for all beta-lactam antibiotics Enzyme mediated degradation #1 mechanism Reduced penetration of drug into bacteria

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