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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
Does erythromycin have a bitter taste?
Yes
26
What may happen after prodrug form of erythromycin?
HIGHER blood levels can occur Some pts get idiosyncratic and reversible cholestatic jaundice damaging the liver
27
List erythromycin pdts with enhanced water solubility
Gluceptate salt used by IV infusion Lactobionate salt used by IV infusion
28
How's Clarithromycin made?
6-O-Methylerythromycin Note: Clarithromycin has NO cl
29
Is erythromycin more lipophilic than Clarithromycin?
No. Clarithromycin is more lipophilic
30
Effect of acid medium on Clarithromycin
Acid stability is enhanced becuz of lack of internal KETAL formation T4, no stomach cramps
31
What's the effect of extensive 1st pass metabolism at C-14 (hydroxylation)
Produces at active metabolite that's active against H. Influenza
32
What differentiates Azithromycin from the others?
M-methyl Grp is inserted btw C-9 & C-10
33
How's the stability of Azithromycin?
Increased stability, t/4 no Ketal formation
34
How's the spectrum of Azithromycin
Broad spectrum Enhanced gram -ve activity
35
Does Azithromycin exhibit postantibiotic effect?
Yes
36
What's dirithromycin hydrolysed to?
Erythromycyclamine
37
Is drug-drug interaction a concern with dirithromycin?
Appears to be less than erythromycin Becuz dirithromycin is not a good substrate for P-450
38
What's the diff btw Ketolides and Erythromycin?
A. No sugar at C-3 (erythromycin has 2 sugars) B. oxidation occurs at C-3 from an alcohol to a ketone.
39
What's the effect of the oxidation at C-3?
Reduced polarity, high lipophilicity => increased bioavailability and reduced degradation in acid medium
40
Whats the Target of Ketolides?
50s subunit, inh protein synthesis
41
Resistant and Ketolides
Ketolides retain activity against macrolide resistant strains that are resistant due to METHYLATION process
42
What are Ketolides most useful against?
Respiratory tract infection
43
Are Ketolides and Macrolides cross-allergenic?
Yes
44
What may cuz the drug-drug int btw Ketolides and telithromycin?
Ketolides is metabolized by P-450 3A4 Telitnromycin is a 3A4 inhibitor
45
List agents that fall under Lincosamides
Lincomycin Clindamycin Clindamycin phosphate
46
What unusual about lincomycin structure?
Contains an unusual thiomethyl amino-octoside
47
How's the stability of Lincosamides?
Very unstable, should be refrigerated
48
Which of the Lincosamides is a natural pdt?
Lincomycin
49
What's the effect of the addition of Cl to clindamycin?
More lipophilic, more active, and better absorbed than lincomycin
50
Whats the Target of clindamycin?
50s ribosome subunit
51
MOA of clindamycin
BacterioSTATIC
52
Is clindamycin cross-resistant with Macrolides?
Yes
53
Compare clindamycin and erythromycin in terms of A. Parental use B. absorption after oral admin
Clindamycin is much less irritating And about 90% is absorbed after oral admin
54
Which clindamycin is used for A. Parental admin B. PO admin
A. Clindamycin C-2 phosphate pro-drug B. the palmitate hydrochloride is a pro-drug for PO
55
Main GI compliant of clindamycin?
Diarrhea
56
Is clindamycin metabolite inactive?
No It's active.
57
List main clinical uses of clindamycin
Gram tve cocci | Anaerobic bacterial inf
58
What has recently reduced the popularity of clindamycin and lincomycin?
PMC

DAST 7 Exam 2 (9 decks)

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