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Pharmacology > Antimicrobials > Flashcards

Antimicrobials Flashcards

1
Q

what is minimal inhibitory concentration (MIC)

A

lowest concentration of an antibiotic that prevents visible growth of the bacteria –> used in calculating an effective clinical dose

clinical dose should be greater than MIC

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2
Q

what is minimal bactericidal growth (MBC)

A

lowest concentration of an antibiotic that results in no growth

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3
Q

compare the MIC and MBC in a true bactericidal agent

A

MBC would be equal to just slight higher than the MIC

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4
Q

what is a disadvantage of using combination therapy

A

some agents only work on multiplying bacteria so if using an agent that causes bacteriostasis, it would be less effective

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5
Q

what do gram positive and gram negative stain as in what are the colors

A

Gram pos has thick peptidoglycan - stains purple

Gram neg has thin peptidoglycan - stains pink

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6
Q

what are some important factors that help in selecting the right agent to treat an infection

A
  • Identity of organism
  • Empiric therapy
  • effect of site of infection on therapy
  • patient factors
  • safety of the agent
  • cost of therapy
  • route of administration
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7
Q

factors that affect if drug can gain access to BBB

A
  • the more lipid soluble it is, the easier to cross BBB
  • the larger the drug, the less likely it is to cross BBB
  • if bound to plasma proteins, less free drug so less likely to gain access to BBB
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8
Q

mechanisms in which resistance can be acquired

A
  • spontaneous mutation of DNA
  • DNA transfer of drug resistance
  • altered expression of proteins in drug-resistant organisms
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9
Q

what are some complications of antimicrobials

A
  • hypersensitivity very common: from urticaria to anaphylactic shock
  • direct toxicity when the antimicrobial affects the host’s cellular processes
  • superinfections: secondary infection develops while treating primary infection
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10
Q

how are the antimicrobials divided in terms of class

A
  • cell wall synthesis inhibitors
  • protein synthesis inhibitors
  • drugs that affect nucleic acid synthesis
  • miscellaneous and urinary antiseptics
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11
Q

what are the cell wall synthesis inhibitors

A
  • Beta Lactams antibiotics: penicillins, cephalosporins, carbapenems, monobactams
  • Vancomycin
  • Daptomycin
  • Bacitracin
  • Fosfomycin
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12
Q

what is an overall benefit of using cell wall synthesis inhibitors

A

mammalian cells do not have cell walls so specifically toxic to bacteria

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13
Q

what is an overall disadvantage of using cell wall synthesis

A

requires actively dividing cells so cell wall synthesis must be occurring in order for it to be inhibited

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14
Q

mechanism of action of beta lactams

A

bactericidal enzymes that bind and inactivate enzymes like penicillin binding proteins (PBPs) involved in final stage of cell wall synthesis –> cell lysis

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15
Q

what are the three mechanisms of bacterial resistance to the beta lactams

A
  • decreased penetration to the target site
  • alteration of target site
  • inactivation of the antibiotic by a bacterial enyzme
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16
Q

how do bacteria decrease the penetration of beta lactams to the target site

A
  • gram neg bacteria have a outer wall that is an effective barrier against beta lactam antibiotics hence antibiotics must use hydrophilic porin to gain access to the PBP (penicillin binding protein)
  • bacteria like pseudomonas do not have porins to gain access hence resistant to antibiotic
  • gram pos bacteria have cell wall that is easily penetrable and do not require presence of porins
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17
Q

what bacterial enzyme do they use to inactivate beta lactams

A

some bacteria such as staph and gram neg bacteria have beta lactamases that inactivate beta lactams

18
Q

what can be given in addition to beta lactams to inhibit the beta lactamase activity of bacteria

(name the beta lactams)

A

beta lactams: penicillin, cephalosporin, carbapenems, and monobactams

beta lactam inhibitors: CAST
Clauvulanic Acid
Sulbactam
Tazobactam

19
Q

name the penicillins

A

ADOPT N-MAC

Amoxicillin
Dicloxacillin
Oxacillin
Penicillin G
Penicillin G benzathine
Penicillin G procaine
Penicillin V
Piperacillin
Ticarcillin

Nafcillin
Methicillin
Ampicillin
Carbenicillin

20
Q

what is Penicillin G active against

A
  • gram pos cocci (except b-lactamase producing staph, penicillin resistant pneumococci, enterococci, MRSA)
  • gram pos rods like listeria and clostridium perfringens
  • gram neg cocci like neisseria (except b-lactamase producing neisseria)
  • most anerobes (except bacteriodes)
  • spirochetes like Treponema Pallidum
21
Q

Penicillin G is drug of choice for what condition

A

Syphilis (benzathine penicillin)
Strep infections (esp to prevent rheumatic fever)
susceptible pneumococci

22
Q

what is Penicillin V mainly used for

A

oropharyngeal infections like strep throat

23
Q

what are the anti-staph penicillin and their importance

A

MOND

Methicillin
Oxacillin
Nafcillin
Dicloxacillin

they inhibit b-lactamase producing staph (except MRSA) –> used for staph infections

24
Q

what are the extended spectrum penicillin and what are the organisms they are fight against

A

Amoxicillin and Ampicillin HHELPSSS kill enterococci

H. Influenza
H. pylori
E. coli
Listeria
Proteus mirabilis
Strep pneumonia
Shigella
Salmonella
Enterococci
25
Q

of the two extended spectrum penicillin, which is better absorbed in the small intestine when administered orally and yield higher urine and blood levels

A

amoxicillin

26
Q

types of people that are usually prescribed amoxicillin and why

A

pregnant women and children

due to its extended spectrum and safety

27
Q

what are amoxicillin and ampicillin used to treat (conditions)

A

major URT infection caused by Strep pneumonia and H. Influenza like:

Otitis media
Pneumonia
Pharyngitis caused by Strep
Skin infections

UTIs too

28
Q

what are the antipseudomonal penicillins

A

Carbenicillin
Ticarcillin
Piperacillin

29
Q

which of the penicillin can penetrate porin channels of bacteria

A

antipseudomonal: Carbenicillin, Ticarcillin, Piperacillin

Extended spectrum: amoxicillin and ampicillin

30
Q

which penicillin is only effective for infections dealing with the urinary tract

A

Carbenicillin

31
Q

what are the antipseudomonal penicillin resistant against (name them)

A

Carbenicillin, Ticarcillin, Piperacillin

Pseudomonas Aeruginosa, Proteus, Enterobacter

32
Q

what are the respiratory penicillin

A

Penicillin G procaine

Penicillin G benzathine

33
Q

why were the respiratory penicillin made and their importance (name them)

A

Penicillin G procaine and Penicillin G benzathine

they were made to prolong the duration of penicillin G by releasing it slowly but persistently in the blood –> reduces cost, need for repeated injections, and local trauma

34
Q

common use of respiratory penicillin

A

Penicillin G procaine and G benzathine

treatment of syphilis
rheumatic fever prophylaxis

35
Q

half life of penicillin

A

generally short like an hour or less with exception of respiratory penicillins

36
Q

best time to give oral penicillin and why

A

1-2 hours before or after a meal because food impairs absorption

37
Q

how are penicillin excreted

A

most via the kidney

  • nafcillin is cleared by biliary excretion
  • oxacillin and dicloxacillin is cleared by both renal and biliary excretion
38
Q

adverse effect of penicillin

A

Hypersensitivity
Allergic Interstitial Nephritis
Neurotoxicity
Secondary Infections

39
Q

adverse effects specific to extended spectrum penicillin and Tircacillin

A

Amoxicillin/Ampicillin: GI disturbances - pseudomembrane colitis and Maculopapular rash

Tircacillin - Hematologic toxicities

40
Q

adverse effects specific to Nafcillin and Oxacillin

A

Nafcillin - Neutropenia

Oxacillin - Hepatitis

41
Q

how do penicillin work with aminoglycosides for a synergistic effect? and what condition do they work synergistically for?

A

work synergistically to treat infective endocarditis

penicillin works mainly on gram pos bacteria while aminoglycosides on gram neg bacteria

penicillin facilitate the movement of aminoglycosides through the cell wall of bacteria by inhibiting cell wall synthesis so that aminoglycoside has access to the protein synthesis which it inhibits

Pharmacology (79 decks)

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