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DAST 7 Exam 2 > Macrolide AB - 5Qs > Flashcards

Macrolide AB - 5Qs Flashcards

1
Q

Explain the meaning of Macrolides AB

A

Macro = large (14-16 memebered ring)

Lied = lactose glycoside

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2
Q

MOA of Macrolide AB

A

ALL are bacterioSTATIC

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3
Q

Are Macrolide ABs acidic or basic?

A

Bases

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4
Q

Name the most common Macrolide ABs used.

A

Salts and esters of erythromycin

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5
Q

Which Macrolide ABs is produced naturally?

A

Erythromycin (Saccharopolyspora erythraea)

All the rest are semi-synthetic

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6
Q

Name the target of Macrolide ABs

A

Inh of protein biosynthesis

Following binding to the 50s ribosomal subunit

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7
Q

What other ABs do Macrolide ABs share a common target with?

What’s the result of this similarity?

A

Lincosamides and chloramphenicol

They are CLINICALLY CROSS RESISTANT with one another

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8
Q

Name agents that are Macrolide ABs

A

Erythromycin
Clarothromycin
Azithromycin
Dirithromycin

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9
Q

What other ABs are equivalent to Macrolide ABs

A

1st gen Cephalosporin and 2nd gen Penicillin

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10
Q

What m.o. is most susceptible to Macrolide ABs

A

Legionella (gram -ve)

Mycoplasma (miscellaneous m.o.)

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11
Q

What m.o. are susceptible to Macrolide ABs

A

Gram tve - strep, staphy, Corneybacterium, B. anthracis

Gram -ve - Legionella, Haemophilis

Anaerobes - propionibacteria

Miscellaneous m.o. - Mycoplasma, Ureoplasma, Chlamydia, Rickettisiae

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12
Q

When do Macrolide ABs find special utility?

A

In pts allergic to Penicillin

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13
Q

List clinical uses of oral Macrolide ABs

A

Upper and lower respiratory tract inf. (Strep Pneumonia)
Upper and lower respiratory tract and otitis media (H. Influenza + sulfonamide)
Mycoplasmal pneumonia
Skin and soft tissue (streptococcus pyrogenes)
Legionnaires dx (Legionella)

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14
Q

What is Macrolide ABs used for PROPHYLAXIS?

A

Bacterial endocarditis (Strep viridans)

Similar to Pen G

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15
Q

What’s Macrolide ABs combo with to treat Mycobacterium avium complex inf in. AIDS, and somewhere STDs?

A

Rifabutin

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16
Q

What Macrolide ABs is used to treat gastric ulcer due to H. Pylori?

A

Clarithromycin

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17
Q

How does resistance dev to Macrolide ABs

A

Alteration of ribosomal target (50S ribosome) by METHYLATION of a ribosomal DNA base leading to weaker binding of AB

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18
Q

What mediates the resistance?

A

R-factor mediated.

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19
Q

Name alternate resistance to Macrolide ABs

A

Efflux pump
Reduced uptake
By destroying enzymes e.g. esterases and phosphotransferases

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20
Q

Effect of food on Erythromycin

A

Absorption is irregular with food.

Propulsive agent (Motilin agonist) causing GI upset

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21
Q

What does liver metabolism of the ff entail
A. Erythromycin

B. Clarithromycin

A

A. N-demethylation

B. C-hydroxylation at C-14

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22
Q

Effect of erythromycin on CP450

A

Erythromycin can inh P-450 enzymes t4 affecting several drugs e.g.
Carbamazepine, cyclosporine, terfernadine, midazolam, warfarin

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23
Q

What is the effect of erythromycin on astemizole and terfernadine?

A

Could lead to v serious CV effect e.g. fibrillation and Arrythmias

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24
Q

What’s the effect of acid medium on erythromycin?

A

Erythromycin is unstable in acid medium due to internal KETAL formation

25
Q

Does erythromycin have a bitter taste?

A

Yes

26
Q

What may happen after prodrug form of erythromycin?

A

HIGHER blood levels can occur

Some pts get idiosyncratic and reversible cholestatic jaundice damaging the liver

27
Q

List erythromycin pdts with enhanced water solubility

A

Gluceptate salt used by IV infusion

Lactobionate salt used by IV infusion

28
Q

How’s Clarithromycin made?

A

6-O-Methylerythromycin

Note: Clarithromycin has NO cl

29
Q

Is erythromycin more lipophilic than Clarithromycin?

A

No.

Clarithromycin is more lipophilic

30
Q

Effect of acid medium on Clarithromycin

A

Acid stability is enhanced becuz of lack of internal KETAL formation

T4, no stomach cramps

31
Q

What’s the effect of extensive 1st pass metabolism at C-14 (hydroxylation)

A

Produces at active metabolite that’s active against H. Influenza

32
Q

What differentiates Azithromycin from the others?

A

M-methyl Grp is inserted btw C-9 & C-10

33
Q

How’s the stability of Azithromycin?

A

Increased stability, t/4 no Ketal formation

34
Q

How’s the spectrum of Azithromycin

A

Broad spectrum

Enhanced gram -ve activity

35
Q

Does Azithromycin exhibit postantibiotic effect?

A

Yes

36
Q

What’s dirithromycin hydrolysed to?

A

Erythromycyclamine

37
Q

Is drug-drug interaction a concern with dirithromycin?

A

Appears to be less than erythromycin

Becuz dirithromycin is not a good substrate for P-450

38
Q

What’s the diff btw Ketolides and Erythromycin?

A

A. No sugar at C-3 (erythromycin has 2 sugars)

B. oxidation occurs at C-3 from an alcohol to a ketone.

39
Q

What’s the effect of the oxidation at C-3?

A

Reduced polarity, high lipophilicity => increased bioavailability and reduced degradation in acid medium

40
Q

Whats the Target of Ketolides?

A

50s subunit, inh protein synthesis

41
Q

Resistant and Ketolides

A

Ketolides retain activity against macrolide resistant strains that are resistant due to METHYLATION process

42
Q

What are Ketolides most useful against?

A

Respiratory tract infection

43
Q

Are Ketolides and Macrolides cross-allergenic?

A

Yes

44
Q

What may cuz the drug-drug int btw Ketolides and telithromycin?

A

Ketolides is metabolized by P-450 3A4

Telitnromycin is a 3A4 inhibitor

45
Q

List agents that fall under Lincosamides

A

Lincomycin
Clindamycin
Clindamycin phosphate

46
Q

What unusual about lincomycin structure?

A

Contains an unusual thiomethyl amino-octoside

47
Q

How’s the stability of Lincosamides?

A

Very unstable, should be refrigerated

48
Q

Which of the Lincosamides is a natural pdt?

A

Lincomycin

49
Q

What’s the effect of the addition of Cl to clindamycin?

A

More lipophilic, more active, and better absorbed than lincomycin

50
Q

Whats the Target of clindamycin?

A

50s ribosome subunit

51
Q

MOA of clindamycin

A

BacterioSTATIC

52
Q

Is clindamycin cross-resistant with Macrolides?

A

Yes

53
Q

Compare clindamycin and erythromycin in terms of
A. Parental use

B. absorption after oral admin

A

Clindamycin is much less irritating

And about 90% is absorbed after oral admin

54
Q

Which clindamycin is used for
A. Parental admin

B. PO admin

A

A. Clindamycin C-2 phosphate pro-drug

B. the palmitate hydrochloride is a pro-drug for PO

55
Q

Main GI compliant of clindamycin?

A

Diarrhea

56
Q

Is clindamycin metabolite inactive?

A

No

It’s active.

57
Q

List main clinical uses of clindamycin

A

Gram tve cocci

Anaerobic bacterial inf

58
Q

What has recently reduced the popularity of clindamycin and lincomycin?

A

PMC

DAST 7 Exam 2 (9 decks)

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