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Pharmacology > Penicillins > Flashcards

Penicillins Flashcards

1
Q

What is among the most commonly used antibiotics in vet med?

A

Penicillins

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2
Q

Why are penicillins called Beta-lactam antibiotics?

A

Because of a ringlike structure in their chemical composition

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3
Q

What other group of antibiotics has a Beta-lactam ring?

A

Cephalosporins

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4
Q

What are the most commonly used penicillians?

A

Natural penicillins
Broad-spectrum aminopenicillins
Penicillinase-resistant or Beta-lactamase-resistant penicillins
Extended-spectrum penicillins

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5
Q

What is an example of a natural penicillin?

A

Penicillin G

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6
Q

What are examples of Broad-spectrum aminopenicillins?

A

Ampicillin

Amoxicillin

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7
Q

What are examples of Penicillinase-resistant or Beta-lactamase-resistant penicillins?

A

Cloxacillin
Dicloxacillin
Oxacillin
Methicillin

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8
Q

What are examples of Exteneded-spectrum penicillins?

A

Ticarcillin
Carbenicillin
Piperacillin

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9
Q

What are pencillins effective against?

A

Many gram-positive bacteria

Lesser number of gram-negative bacteria

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10
Q

Are penicillins bactericidal or bacteristatic?

A

Bactericidal

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11
Q

How do penicillins work primarily?

A

by attaching to & blocking the bacterial enzymes needed to assemble the cell wall during bacterial cell division

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12
Q

What does blocking the bacterial enzymes needed to assemble the cell wall accomplish?

A

Makes the resulting wall more structurally unstable

Makes the bacterium more prone to lysis from osmotic imbalances

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13
Q

What explains why one type of penicillin may be more effective against a bacterial population than another type?

A

Different penicillins affect different wall-building enzymes

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14
Q

What is a bacterial strain found on the skin and has acquired resistance to all penicillins?

A

Methicillin-resistant Staphylococcus aureus

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15
Q

How has MRSA become resistant to all pencillins?

A

The targeted wall-building enzymes to which penicillin attaches changes molecular shape making penicillins unable to dock & disrupt enzymes

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16
Q

Why should bacteriostatic antimicrobials not be used simultaneously with Beta-lactam antibiotics?

A

Because Beta-lactam antibiotics need the bacterial colony to be actively replicating and bacteriostatic antimicrobials inhoibit division of bacteria

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17
Q

Penicillins are well absorbed from where?

A

The injection site and GI tract

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18
Q

Which penicillin is inactivated by gastric acid and thus should never be given orally

A

Penicillin G

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19
Q

Because penicillin molecules are hydrophilic, it will not reach therapeutic concentrations where?

A

Globe of the eye
Brain
Prostate

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20
Q

Why are penicillin concentrations much higher in the urine than in the blood?

A

Because penicillin is actively transported by the renal tubules into the forming urine

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21
Q

Why are penicillins more commonly used to treat bacterial cystitis?

A

Because urine penicillins will exceed the MIC for many bacteria found in the kidneys, bladder or genitourinary tract

22
Q

What is the selection of particular antimicrobial drug before the results of a culture & sensitivity test are returned?

A

Empiric treatment

23
Q

Why are penicillins more effective against gram-positive bacteria?

A

Because they have a cell wall that is readily accessible to penicillin drug molecules

24
Q

Why are penicillins less effective against gram-negative bacteria?

A

Because they have an outer capsule that penicillins can only penetrate by slipping through porins

25
Q

How do gram-negative bacteria become resistant to penicillin drugs?

A

By genetically decreasing the size of the porins

26
Q

What particularly resistant gram-negative bacteria is commonly found in otitis externa or necrotic tissue?

A

Pseudomonas

27
Q

What type of penicillins are likely to have much chance to be effective against Pseudomonas?

A

Only the most aggressive extended-spectrum penicillins
Ticarcillin
Carbenicillin

28
Q

What is it called when a strain of bacteria that develops resistance to one type of penicillin, the bacteria will also be resistant to many of the other penicillins?

A

Cross-Resistance

29
Q

What bacteria has acquire resistance to many penicillins because it produces an enzyme that attacks the penicillin’s Beta-lactam rings?

A

Staphylococci spp

30
Q

What group of penicilins are not affected by bacterial Beta-lactamase enzymes and are used in the treatment of bovine mastitis?

A

Oxacillin
Dicloxacillin
Cloxacillin
Methicillin

31
Q

What happens when a penicillin drug is combined with another compound, producing a strong modified penicillin resistant to the Beta-lactamase enzyme?

A

Pencillin drugs that are normally inactivated by Beta-lactamase can be chemically protected from the enzyme

32
Q

What are two examples of compounds that are added to penicillins that produce a potentiated penicillin compound capable of withstanding bacterial lactamase enzymes?

A

Clavulanic acid (amoxicillin) and Sulbactam (ampicillin)

33
Q

When Clavulanic acid or sulbactam combines with the Beta-lactamase enzymes, preventing the enzyme combining with and destroying the penicillin, what does it allow the penicillin to do?

A

Survive to attach to the cell wall enzymes and prevent normal cell wall formation

34
Q

Why are penicillins considered quite safe?

A

Because their target bacterial cell walls & mammalian cells only have cell membranes, not cell walls

35
Q

What is the most common type of adverse reaction seen with penicillins?

A

Hypersensitivity

36
Q

What are the common signs of a hypersensitive reaction to penicillin?

A 
Mild skin rash
Hives
Swelling of the lymph nodes
Eosinophilia
Neutropenia
Fever
37
Q

Life-threatening anaphylactic shock is more common with what kind of penicillin product?

A

Injectable

38
Q

What happens when penicillin is given orally?

A

Penicillins may destroy beneficial gram-positive bacteria in the lumen of the intestinal tract, which allows more pathogenic, penicillin resistant bacteria to proliferate

39
Q

What is the term to describe when penicillins destroy beneficial gram-positive bacteria and allow more pathogenic bacteria?

A

Superinfection or Suprainfection

40
Q

Superinfection or Suprainfection causes diarrhea and death in what species?

A

Guinea pigs
Ferrets
Hamsters
Rabbits

41
Q

In what species should penicillins be used with caution in?

A

Snakes
Birds
Turtles
Chinchillas

42
Q

What group of pencillins are produced by mold and includes Penicillin G?

A

Natural penicillins

43
Q

What penicillin has a narrow spectrum of activity and many bacteria are now resistant to?

A

Penicillin G

44
Q

What are the 3 forms of penicillin G?

A

An aqueous solution
Suspension form with procaine
A longer-acting suspension combined with benzathine

45
Q

What form of penicillin G contains a local anesthetic that may be prohibited in horses and last in the horse’s system for 2 weeks?

A

Suspension combines with procaine

46
Q

What group of penicillins include Ampicillin and amoxicillin, has a wider effective spectrum against gram-negative bacteria and is susceptible to destruction and inactiviation by Beta-lactamase?

A

Aminopenicillins

47
Q

What can the injectable form of amipicillin and amoxicillin be formulated into that forms a slow-release suspension and prolongs the absorption of aminopenicillins?

A

Trihydrate

48
Q

What group of penicillins are naturally resistant to the effects of the bacterial enzyme, has a low spectrum of activity?

A

Beta-lactamase-resistant penicillins

49
Q

Why do Beta-lactamase-resistant penicillins have a low spectrum of antibacterial activity?

A

They do not penetrate the outer membrane of gram-negative bacteria

50
Q

Beta-lactamase-resistant penicillins are used most commonly to treat what?

A 
Staphylococcal osteomyelitis (bone infections)
Staphylococcal pyoderma (skin infections)
Staphylococcal mastitis
51
Q

What group of penicillins have a wider spectrum than other penicillins, are expensive, able to penetrate the outer membrane of gram-negative bacteria and are susceptible to Beta-lactamase enzymes?

A

Extended-spectrum penicillins

52
Q

What are extended-spectrum penicillins used to treat?

A

Severe, resistant gram-negative infections

Pharmacology (21 decks)

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