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Musculoskeletal System > Pharm Antibiotics > Flashcards

Pharm Antibiotics Flashcards

To understand the pharmacology as well as the viability of tetracycline, clindamycin, and chloramphenicol in treating listed diseases

1
Q

Clinically important tetracyclins

A 
Chlortetracycline
Oxytetracycline
tetracycline
demaclocycline
methacycline
doxycycline
minocycline
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2
Q

Properties of tetracyclins

A

Poorly water soluble and are formulated as hydrochlorides

GI absorption is by the presence of food in the GI

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3
Q

MOA of tetracycline

A

Reversibly blocks the 30s ribosome to prevent protein synthesis
by binding, it prevents charged tRNA from binding to the loading A site and stops translation

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4
Q

Tetracyclins

A

chemical backbone = 4 rings
different members arise from different substituents on the ring
new member: Tigecycline

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5
Q

Tigecycline

A

Broad-spectrum
Long half life
Improved resistance profile
Can be given with proton pump inhibitors (to tx helicobacter induced ulcers)
Low resistance hospital-aquired (nosocomial) infections

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6
Q

doxycycline

minocycline

A

not affected by food
No decrease in absorption even in the presence of food
100% bioavailability via IV

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7
Q

High pH effect

A

Decrease tetracycline’s effect?

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8
Q

mycoplasmas

A

cause pneumonia

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8
Q

Rikettsiae

A 
Rocky mountain spotted fever
Purple rashes (pectechaie)=> bleeding underneath the skin
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9
Q

What drugs are not substrates for efflux pumps (produced by resistant strains)?

A

Doxycycline
minocycline
tigecycline

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10
Q

Most effective types of bacterial resistance

A

Efflux pumps

Proteins that protect the ribosomes

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11
Q

Three mechanisms that convey bacterial resistance to tetracycline

A

1) Impaired influx or enhanced efflux(of tetracycline) by an active transport protein pump, 2) Ribosome protection and 3) Enzymatic inactivation of the drugs
In simple terms…..
Bacteria will have a mutation that will produce efflux pumps that are selective for antibiotics
The drug is pumped out by active transport

Bacteria produce proteins that bind to the antibiotics
Bacterial enzymes can completely degrade the drugs

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12
Q

Contraindications of tetracyclines

A

Not good for children:
The drug crosses the placenta, breast milk
bind to calcium and damage bones
bind to teeth

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13
Q

Enterohepatic circulation

A

drugs absorbed from the liver => secreted into the bile
a fatty meal => drugs are re-secreted to the GI tract via bile, so it can get reabsorbed again => increases the long half life of the tetracyclines

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14
Q

Advantages of tetracyclines

A

Improve patient compliance

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15
Q

Clinical Uses : Chlymadiae

A

Sclera of the eye is irritated, red, yellow pus,

Chlortetracycline tx. Chlymadiae conjunctivitis

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16
Q

What is the problem with the combination therapy of tetracycline + proton pump inhibitor to treat helicobacter pylori-induced ulcers?

A

change the pH = high pH which will make tetracycline ineffective
need acid to absorb tetracycline

Change the order of how you give the two drug
-wait 8 to 12 hours
give tetracycline first

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17
Q

Demeclocycline

A

prevent the action of ADH
Tx tumors that secrete ADH
central diabetes insipidus?

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18
Q

Tetracyclins used in combination with aminoglycosides

A

Tx plague, tularemia and brucellosis

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19
Q

Adverse effects of tetracyclines

A

MOST IMPORTANT : effect on BONE

Tetracyclines are deposited in bone and teeth and are contraindicated in children less than 8yrs old and pregnant women

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20
Q

How can you reduce the adverse effect on kidneys

A

adjust dose

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21
Q

Adverse effect of Demaclocycline

A

Photosensitivity

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22
Q

MOA of Clindamycin

A

Binds exclusively to the 50S ribosome �

block the whole protein synthesis

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23
Q

1st mechanism of resistance to clindamycin

A

Mutation of the ribosomal receptor site
Drug will not have high affinity for the target site
need high conc. of drug but can’t be achieved physiologically

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24
Q

Mechanism of Clindamycin

A

Binds to 50S ribosome and inhibits protein synthesis

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25
Q

Clindamycin binding to plasma protein

A

90% except in CNS

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26
Q

Combination clindamycin and cephalosporin or aminoglycosides �

A

used for prophylaxis

Tx penetrating wounds of the abdomen and the gut

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27
Q

Clindamycin combination with pyrimethamine

A

inhibit tetrahydrolate synthase
inhibit synthesis of folate from PABA
used for AIDS-related toxoplamosis of the brain�

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28
Q

Gray baby syndrome

A

Toxicity in newborn infants: gray baby syndrome (vomiting, flaccidity, hypothermia, gray color shock and collapse)
Must be used with caution in infants
Unique to chloramphenicol!!!!!

The UDP-glucuronyl transferase enzyme system of infants, especially premature infants, is immature and incapable of metabolizing the excessive drug load.
Insufficient renal excretion of the unconjugated drug.

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29
Q

Broad spectrum activity of tetracyclines

A

antimicrobial activity against gram + and gram - bacteria including anaerobes, chlamydiae, myocoplasma, rikettsiae, ameobas

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30
Q

How does tetracycline enter susceptible bacteria?

A

simple diffusion and through active transport

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31
Q

What if the antibiotic does not have high affinity for the efflux pump?

A

Resistance is avoided

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32
Q

What is the drug that is effect even against the Tet(A) efflux-expressing gram - strains having resistance to the older tetracycline like doxycycline and minocycline

A

Tegecycline

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33
Q

Which tetracycline resistance protein confers resistance to tetracycline, doxycycline, and minocycline but not to tigecycline?

A

Tet (M)

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34
Q

Which agent has Tet (K) that confers resistance to tetracycline but not to doxycycline, minocycline, or tigecycline

A

Staphylococcus

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35
Q

Tigecycline is effective in the presence of which Tet proteins

A

Tet A, Tet M
Tet K
Tet M

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36
Q

Which gram strains express Tet M

A

gram positive

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37
Q

Gram + strains that express Tet M have what kind of protection

A

Ribosomal

38
Q

Which species have intrinsic resistance to all tetracyclines?

A

proteus and psudomonas aeroginosa

39
Q

Tet (A)

A

Gives gram negative strains efflux pumps for doxycycline and minocycline.
NOT EFFECTED: Tigecycline

40
Q

Tet (K)

A

Confers resistance to tetracyclines in staphylococcus.

NOT EFFECTED: Tigecycline, Doxycycline, Minocycline

41
Q

Tet (M)

A

Ribosomal protection expressed by gram + strains. Resistance to Doxy, Mino, Tetra.
NOT EFFECTED: Tigecycline

42
Q

What does food in the GI do to the absorption of tetracyclines?

A

Impairs it

except in the case of doxycycline and minocycline

43
Q

Which drugs have 95-100% bioavailability?

A

doxycycline and minocycline

44
Q

What other products can impair absorption of tetracyclines in the GI tract?

A

Ingestion of dairy products, antacids or the presence of alkaline pH, cations like Ca2+, Mg2+, Fe2+ or Al3+ can cause tetracycline to become more insoluble

45
Q

The site where tetracycline are not distributed to

A

CNS
only a small fraction of the administered dose is found
otherwise, tetracyclines are widely distributed

46
Q

Which tetracycline attain high concentration in saliva and tears making it useful for tx of meningococal carrier state?

A

minocycline

*remmber they can’t get to the CNS)

47
Q

What are two main routes of excretion of tetracyclines?

A

Urine

Enterohepatic circulation

48
Q

Which drugs are not eliminated by renal mechanisms and adjustments of these drugs are not required in renal failure?

A

doxycycline and tigecycline

49
Q

Which tetracycline has a half life of 36 hrs?

A

tigecycline

50
Q

Which tetracyclines have half lives of 16-18 hrs (long lasting)?

A

doxycycline

minocycline

51
Q

Clinical uses of tetracyclines

A 
Mycoplasma pneumoniae
Ricketssiae (Rocky Mountain Spotted Fever)
Chlamydial conjunctivitis
Helicobacter pylori-induced ulcers
Vibrio infections (cholera) 
Protozoa/entamoeba
ADH secreting tumors 
Cholera (Vibrio)
Malaria
Parrot Fever (Chlamydia)
Lyme Disease (Borrelia)
Q Fever (Coxiella)
Anthrax
Trachoma
52
Q

Tx of vibro infections

A

tetracyclines have rapid actions against cholera (stop shedding of vibro). However resistance may be emerging

53
Q

What is the drug of choice for chlamydial conjunctivitis

A

Chlortetracycline

eye drops

54
Q

What can treat ADH secreting tumors?

A

Demeclocycline

55
Q

Which protozoal infections are tx with tetracyclines

A

Entamoeba histolytica

plasmodium falciparum

56
Q

Miscellaneous uses of tetracyclines

A

acne, exercitation of bronchitis, community acquired pneumonia, Lyme disease, relapsing fever, leptospirosis and Mycobacterium marinum

57
Q

How is tigecycline administered?

A

IV

58
Q

Tigecycline is effective against what types of species

A

many tetracycline resistance strains

59
Q

Tigecycline has activity against the following strains

A

Has activity against Coagulase negative staphylococci and Staphylococci aureus and methicillin-resistant strains
Streptococci, penicillin susceptible and resistant, enterococci, vancomycin-resistant strains and gram –ve rods

60
Q

Clinical uses of tigecycline

A

Enterobacteriacae, multiple resistant strains of Acenitobacter species, Rickettsiae, chlamydia and legionella

61
Q

Tetracyclines disrupt normal flora. What are some of the effects?

A

overgrowth of pseudomonas, proteus, staphylococci, resistant coliforms, clostridia and candida may give rise to anal pruritus, vaginal or oral candidiasis (yeast infection) or enterocolitis with shock and death

62
Q

Hepatic necrosis�

A

an adverse effect seen in pregnancy if pt his given IV tetracycline

63
Q

Renal insufficiency

A

tetracycline can accumulate
nitrogen retention
exceptions: doxycycline and tigecycline

64
Q

Vestibular reaction → dizziness, vertigo

A

Doxycycline

65
Q

Agents susceptible to clindamycin

A

Streptococci, staphylococci and pneumococci �ANaerobic Bacteriodes species �

66
Q

Agents resistant to clindamycin

A

enterococci and gram-ve aerobic �

67
Q

Bacterial resistance to Clindamycin

A

• Change in one AA can result of loss of affinity for the drug to the bacterial binding site
o Need a larger concentration of drug to achieve the same effect
• Constitutive expression of methylase will result in modification of the drug’s receptors
• Gram (—) are intrinsically resistant due to lack of permeability of cell wall

Enzymatic inactivation of clindamycin

68
Q

What sites do clindamycin penetrate well?

A

abscesses … treat pelvic abscesses

69
Q

Where does clindamycin concentrate?

A

phagocytic cells via active transport

70
Q

Where does clindamycin metabolize?

A

liver

71
Q

Where does clindamycin get excreted?

A

urine and bile

72
Q

Clindamycin and clinical use for the heart

A

prohpylaxis against endocardiatis in patients with vavular heart diseas�

73
Q

Clindamycin combined with primaquine

A

Forms an effective alternative to trimethoprim-sulfamethozazole against moderate to severe pneumocystis jirovei (result of AIDS or corticosteriods) in AIDS patients�

74
Q

Adverse effects of Clindamycin

A

impaired liver function - jaundice
neutropenia
severe diarrhea
pseudo membranous colitis - due to clostridium difficile
***Can create a super bug by killing off normal flora → bacteria that remain grow uninhibited and have resistance

75
Q

Chloramphenicol drug MOA

A

inhibits bacterial 50S ribosomes and prevent protein synthesis VIA INHIBITING TRANSPEPTIDATION

76
Q

Which agent is Chloramphenicol active against but not against Chlamydia

A

Rickettsia

77
Q

Which other agents are highly susceptible to chloramphenicol?

A

Haemophilus influenza, N meningitis and bacteriodes

78
Q

What enzyme is produced to confer resistance to chloramphenicol?

A

a plasmid encoded enzyme

CHLORAMPHENICOL ACYL TRANSFERASE

79
Q

Unlike tetracyclines and clindamycin, how is chloramphenicol distributed?

A

widely distributed throughout the body including the CNS and body fluids

80
Q

How is chloramphenicol metabolized/eliminated?

A

Conjugated in the liver (glucuronic acid) and eliminated in urine

81
Q

Which drug’s dose must be reduced in newborns and premature infants?

A

Chloramphenicol

because it can cause grey baby syndrome

82
Q

which two drugs’ doses do not need to be reduced in renal insufficiency?

A

clindamycin and chloramphenicol

83
Q

What is the second line drug for cholera?

A

Chloramphenicol

84
Q

Tx of serious rickettsial infection such as typhus and rocky mountain spotted fever

A

chloramphenicol

85
Q

Alternative to beta-lactam against meningococcal meningitis

A

chloramphenicol given in its wwho are either hypersensitive to penicillin or if the infection is penicillin-resistant

86
Q

Tx brain abscess (staph brain abscess)

A

chloramphenicol

87
Q

Topical tx of eye infection

A

chloramphenicol has good penetration into ocular tissues and aqueous humor

88
Q

why is chloramphenicol rarely used?

A

toxic

increased resistance

89
Q

Adverse effect

A

GI tract: Adults (but not children) commonly develop nausea, vomiting and diarrhea
�
Bone marrow disturbances: decreased production of red blood cells
Aplastic anemia (idiosyncratic) may be reversible but could be fatal

90
Q

Important Chloramphenicol effect in women

A

Risk of oral or vaginal candidiasis may occur (due to alteration of normal flora)

91
Q

What does chloramphenicol inhibit that reduces the rate of metabolism of phenytoin, tolbutamide, chlorpropamide, and warfarin

A

a CYP inhibitor
increase their half life
Need to adjust the doses of those drugs to avoid toxicity

92
Q

On which drugs does chloramphenicol have antagonistic effect?

A

penicillin (cell wall synthesis inhibitors) and aminoglycosides �(protein synthesis inhibitors)

Musculoskeletal System (27 decks)

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