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Pharmacology > Macrolides, Clindamycin, Streptogramins > Flashcards

Macrolides, Clindamycin, Streptogramins Flashcards

1
Q

Prototype drug of macrolides

A

Erythromycin

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2
Q

Are semisynthetic derivatives of erythromycin

A

Clarithromycin and azithromycin

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3
Q

Are a group of closely related compounds characterized by a macrocyclic lactone ring (14 to 16 atoms) to which deoxy sugars are attached

A

Macrolides

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4
Q

General structure: macrolide ring and 2 sugar moieties desosamine and cladinose attached to a 14 atom lactone ring

Poorly soluble in water but dissolves readily in organic solvents

A

Erythromycin

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5
Q

Is a combination of two streptogramins - _____, a streptogramin B and _____, a streptogramin A in a 30:70 ratio

A

Quinupristin - dalfopristin

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6
Q

Shares the same ribosomal binding site as the macrolides and clindamycin and thus inhibit protein synthesis in an identical manner

A

Streptogramins

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7
Q

Quinupristin-dalfopristin is rapidly bactericidal for most susceptible organisms except ______, which is killed slowly

A

Enterococcus faecium

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8
Q

Streptogramin has resistance to _______ due to modification of quinupristin binding site and enzymatic inactivation of dalfopristin, or efflux

A

E. Faecalis

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9
Q

Quinupristin-dalfopristin is active against

A

Gram positive cocci including
multidrug resistant strains of streptococci, penicillin resistant strains of S pneumoniae, methicillin susceptible and resistant strains of stap and E. faecium

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10
Q

Quinupristin-dalfopristin is eliminated by what route?

A

Fecal route

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11
Q

True or false: dose adjustment is not necessary in Quinupristin-dalfopristin for cases of renal failure, peritoneal dialysis or hemodialysis

A

True

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12
Q

True or false: Quinupristin-dalfopristin significantly inhibit CYP3a4 which metabolizes warfarin, diazepam, cisapride, cyclosporine etc

A

True (dosage reduction of cyclosporin may be necessary)

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13
Q

Clinical use of Quinupristin-dalfopristin

A

Treatment of infections caused by staphylococci or by vancomycin resistant strains of E faecium

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14
Q

Principal toxicities of Quinupristin-dalfopristin

A

Infusion related events such as pain at infusion site and arthralgia-myalgia syndrome

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15
Q

Is a chlorine subsituted derivative of lincomycin, an antibiotic that is elaborated by Streptomyces lincolnensis

A

Clindamycin

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16
Q

Like erythromycin, it inhibits protein synthesis by interfering with the formation of initiation complexes and with aminoacyl translocation reactions

A

Clindamycin

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17
Q

The binding site for clindamycin is on the ____ subunit of the bacterial ribosome identical with erythromycin

A

50S subunit

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18
Q

Clindamycin, 0.5-5 mcg/ml inhibits the ff:

A

Streptococci, staphylococci and pneumococci

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19
Q

Organisms resistant to clindamycin:

A

Enterococci and gram negative aerobic organism

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20
Q

Usually susceptible to clindamycin:

A

Bacteroides sp and other anaerobes (+ and -)

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21
Q

Resistance to clindamycin, which generally confers cross resistance to macrolides, is due to:

A
  1. Mutation of ribosomal receptor site
  2. Modification of the receptor by a constitutively expressed methylase
  3. Enzymatic inactivation of clindamycin
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22
Q

True or false: clindamycin is about 90% protein bound

A

True

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23
Q

Clindamycin penetrates well into most tissues except for _____ and ______.

A

Brain and CSF

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24
Q

Clindamycin is metabolized by the _______, and both active drug and active metabolites are excreted in _____ and ______.

A

Liver
Bile
Urine

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25
Q

True or false: clindamycin penetrates well into abscesses and is actively taken up and concentrated by phagocytic cells

A

True

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26
Q

Clinical use of clindamycin

A

Treatment of skin and soft tissue infections caused by strep and staph

Active against community acquired strains of MRSA

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27
Q

True or false: clindamycin is also indicated for the treatment of infections caused by bacteroides sp and other anaerobes

A

True

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28
Q

Drugs used to treat penetrating wounds of the abdomen and gut; infections originating in the female genital tract (eg PID, septic abortion) and lung abscess

A

Clindamycin + aminoglycoside or cephalosporin

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29
Q

Clindamycin is now recommended rather than erythromycin for prophylaxis of ______ in pts with specific valvular dse who are undergoing _____ procedures and have allergy to penicillin

A

Endocarditis

Dental procedures

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30
Q

Is an effective alternative to Trimethoprim-sulfamethoxazole for moderate to moderately severe P. jiroveci pneumonia in AIDS pts

A

Clindamycin + primaquine

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31
Q

Indicated for AIDS related toxoplasmosis of the brain

A

Clindamycin + pyrimethamome

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32
Q

Administration of clindamycin is a risk factor for diarrhea and colitis due to ______

A

C. Difficile

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33
Q

True or false: the antibacterial action of erythromycin and other macrolides may be excitatory or bacteriostatic, particularly at higher concentrations for susceptible organisms.

A

False. Inhibitory or bactericidal

34
Q

True or false: erythromycin’s activity is enhanced at acidic pH.

A

False. Alkaline pH

35
Q

Inhibits protein synthesis occurring via binding to the 50S ribosomal RNA.

The binding site is near the peptidyltransferase center and peptide chain elongation is prevented by blocking of the polypeptide exit tunnel

A

Erythromycin

36
Q

True or false: in clindamycin, peptidyl-tRNA is dissociated from the ribosome.

A

False. Erythromycin

37
Q

Erythromycin is active against susceptible strains of:

A

Gram positive organisms ( pneumococci, strep, staph and corynebacteria)

Gram negative organisms
(Neisseria sp, Bordetella pertussis, Bartonella sp, Rickettsia sp.

38
Q

True or false: T. Pallidum and Campylobacter sp. are susceptible to erythromycin.

A

True

39
Q

True or false: H. influenzae is less susceptible to erythromycin

A

True

40
Q

Resistance to erythromycin is usually ________-encoded?

A

Plasmid-encoded

41
Q

_____ and _____ are the most important resistance mechanisms in gram positive organisms

A

Efflux and Methylase production

42
Q

Constitutive methylase production confers resistance to structurally unrelated but mechanistically similar compounds such as clindamycin and streptogramin B called ______, which share the same ribosomal binding site

A

Macrolide-lincosamide-streptogramin B or MLS type B

43
Q

Erythromycin base is destroyed by _________ and must be be administered with ______ coating

A

Stomach acid, enteric coating

44
Q

True or false: food does not interfere with absorption while taking erythromycin

A

False

45
Q

_____ and ____ are fairly acid resistant and somewhat better absorbed

A

Stearates and esters

46
Q

Is the best absorbed oral preparation for erythromycin

A

Erythromycin estolate (lauryl salt of propionyl ester of erythromycin)

47
Q

True or false: dialysis can removed erythromycin

A

False. Large amount is excreted in the bile and lost in feces and only 5% excreted in the urine

48
Q

True or false. Erythromycin is distributed widely except to the brain and CSF

A

True

49
Q

True or false: erythromycin is taken up by PMN leukocytes and macrophages

A

True

50
Q

True or false: erythromycin does nit traverse the placenta and reaches the fetus

A

False

51
Q

Traditional drug of choice in corynebacterial infections ( diphtheria, sepsis, erythrasma) and in respiratory, neonatal, ocular or genital chlamydial infections

A

Erythromycin

52
Q

True or false. Macrolide resistance is increasing in pneumococci and M. pneumoniae

A

True

53
Q

True or false. Erythromycin resistance in staph and in strains of Group A strep has made macrolides less attractive as first line agents for treatment of pharyngitis and skin and soft tissue infections

A

True

54
Q

Although ________ is the best absorbed salt, it imposes the greatest risk of adverse reactions

A

Erythromycin estolate

55
Q

Oral erythromycin is sometimes combined with ______ or ________ for preoperative preparation of the colon

A

Oral neomycin or kanamycin

56
Q

__________ is the most common reason for discontinuing erythromycin and substituting another antibiotics

A

Gastrointestinal intolerance

57
Q

Erythromycin estolate can produce _______, probably as a hypersensitivity reaction

A

Acute cholestatic hepatitis

58
Q

True or false: most pts can recover from acute cholestatic hepatitis, but it recurs if the drug is readministered

A

True

59
Q

Erythromycin metabolites inhibit CYP P450 enzymes and thus increase serum concentrations of:

A 
Theophylline
Warfarin
Cyclosporine
Methylprednisolone
Oral digoxin (increase bioavailability)
60
Q

Is derived from erythromycin by addition of a methyl group and has improved acid stability and oral absorption compared with erythromycin

A

Clarithromycin

61
Q

Clarithromycin is similar with erythromycin with respect to antibacterial activity except it is more active against:

A

Mycobacterium avium complex

62
Q

Clarithromycin also has activity against:

A

M. leprae
T. gondii
H. influenzae

63
Q

True or false: clarithromycin has a longer half life (6 hr) compared with erythromycin which permits twice daily dosing

A

True

64
Q

Clarithromycin is metabolized in the _____. The major metabolite is ______.

A

Liver

14 hydroxyclarithromycin

65
Q

True or false: clarithromycin is eliminated in the urine

A

True

66
Q

True or false: in clarithromycin, dosage requirement is not needed for patients with creatinine clearances of less than 30 ml/min

A

False. Dosage reduction is recommended

67
Q

What is the advantage of giving clarithromycin compared with erythromycin?

A

Lower incidence of GI intolerance and less frequent dosing

68
Q

Is a 15 atom lactone macrolide ring compound, is derived from erythromycin by addition of a methylated nitrogen into the lactone ring

A

Azithromycin

69
Q

Azithromycin is:

a
A. active against:

B. slightly less active than erythromycin and clarithromycin against:

C. Slightly more active against:

D. Highly effective against:

A

A. M. avium complex and T. gondii

B. Staph and strep

C. H. influenzae

D. Chlamydia sp.

70
Q

Azithromycin may prolong ________ due to an effect on potassium ion channels

A

QT interval ( prolongation of the QT interval can lead to torsades de pointes arrythmia

71
Q

True or false: recent studies have suggested that azithromycin may be associated with a small increased risk of cardiac death

A

True

72
Q

True or false: azithromycin is slowly released from tissues ( half life 2-4 days ) to produce an elimination half life approching 3 days

A

True

73
Q

Has unique properties that permit once daily dosing and shortening of the duration of treatment in many cases

A

Azithromycin

74
Q

When should azithromycin be administered:

A

1 hr before or 2 hrs after meals

75
Q

True or false: azithromycin is rapidly absorbed and well tolerated orally

A

True

76
Q

True or false: Because azithromycin has a 15 member lactone ring, it does not inactivate CYP P450 enzymes and therefore free of drug interactions

A

True

77
Q

Are semisynthetic 14 membered ring macrolides, differing from erythromycin by substitution of a 3 keto group for neutral sugar L-cladinose

A

Ketolides

78
Q

E.g of ketolides approved for limited clinical use

A

Telithromycin

79
Q

Telithromycin is now indicated only for the treatment of ______ in the USA

A

Community acquired bacterial pneumonia

80
Q

Telithromycin was removed as an indication for respiratory tract infections due to:

A

It can result in hepatitis and liver failure

81
Q

Telithromycin is also contraindicated in pts with _________

A

Myasthenia gravis ( it may exacerbate this condition)

Pharmacology (12 decks)

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