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PoD Test 2 > Macrolides, Clindamycin, Chloramphenicol > Flashcards

Macrolides, Clindamycin, Chloramphenicol Flashcards

1
Q

What is the MoA of macrolides?

A

Reversible binds to the 50S-ribosomal subunit of bacteria, decreasing protein synthesis

Bacteriostatic

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2
Q

What are the mechanisms of resistance to macrolides?

A

Decreased permeability of the cell envelope

Alteration in 50S ribosomal receptor site

Enzymatic inactivation of erythromycin by esterases

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3
Q

Describe the absorption of erythromycin.

A

Erythromycin base is rapidly inactivated by gastric acid

Absorbed better in fasting state

Emycin estolate - not affected by food

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4
Q

Describe the distribution of macrolides..

A

Distributes in tissues longer than in blood

Very high concentrations in alveolar macrophages and leukocytes

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5
Q

What is significant about azithromycin tissue concentrations.

A

10-100x serum concentrations

Allows for 5 day course of therapy

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6
Q

How is erythromycin metabolized/excreted?

A

Inactivated in the liver by demethylation

Biliary excretion mostly, small percentage in urine

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7
Q

What is clarithromycin metabolized/excreted?

A

Metabolized in the liver by oxidation and hydrolysis

20-30% of drug excreted into urine unchanged

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8
Q

How is azithromycin metabolized/excreted?

A

Small proportion is metabolized

Biliary excretion

T1/2 = 68hrs - slow release from tissue, 5 day regimen

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9
Q

What are the ADRs of erythromycin?

A

GI - abdominal cramps

Thrombphelbitis

Cholestatic hepatitis (avoid estolate in pregnancy)

Large IV doses - ototocicity, QT prolongation

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10
Q

What are the ADRs of clarithromycin/azithromycin?

A

GI - less severe than erythromycin

HA

Dizziness

Allergic reaction

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11
Q

What are the drug interactions for erythromycin/clarithromycin?

A

Inactivates p450

Decreased metabolism: Theophylline, Warfarin, Carbamazepine, cyclosporine

*azithromycin doesn’t affect p450

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12
Q

What is the spectrum of activity for erythromycin?

A

G+ (staph and strep)

Atypicals

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13
Q

What is the spectrum of activity of Clarithromycin/Azithromycin?

A

H. flu, M. Cat** (difference from erythro.)

MAC

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14
Q

What is a prevpak?

A

Treatment for H. pylori

Amoxicillin 1gm BID, PPI BID, Clarithromycin 500mg BID

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15
Q

What are the indications for the macrolides?

A

Penicillin allergy

CAP (clar. and azith.)

M. pneumoniae

Legionnaire’s disease

Chlamydia trachomatis

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16
Q

What is the structure and MoA of clindamycin?

A

Derived from lincomycin, but more potent

Binding of 50S ribosome, inhibiting protein synthesis

17
Q

What is the bioavailability and metabolization of clindamycin?

A

Bio. - 90%, food delays absorption

Metabolized by liver

18
Q

What is the spectrum of activity for clindamycin?

A

Strep/Staph

Anaerobes (Bacteroides, Clostridium, Peptostrep. peptococcus)

Toxoplasmosis if sulfonamide allergy

19
Q

What are the ADRs of clindamycin?

A

Allergic reaction

Diarrhea

C. diff

Hepatotoxicity

20
Q

What is the MoA of Chloramphenicol?

A

Reversibly binds to the larger 50S subunit of the 70S ribosome

21
Q

What has to happen for chloramphenicol to be active?

A

Must be hydrolyzed in the intestines

IV form has incomplete hydrolysis - 70% serum concentrations of oral

22
Q

How is chloramphenicol distributed/metabolized?

A

Excellent CSF concentrations - 30-50% w/o inflammation

Metabolism via glucuronidation in the liver

Wide variations in metabolism and excretion in children

23
Q

What is the spectrum for chloramphenicol?

A

Gram positive and negative

Aerobes and Anaerobes

Rickettsia/Chlamydia

24
Q

What are the ADRs for chloramphenicol?

A

Hematologic - reversible bone marrow depression (anemia, leukopenia, thrombocytopenia)

Idiosyncratic aplastic anemia

25
Q

What are the indications for chloramphenicol?

A

Bacterial meningitis (H. influenza, Strep pneumo, N. meningitidis

Rickettsial infections

PoD Test 2 (23 decks)

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