MACROLIDES AND AZALIDES

Question 1

What is the prototype drug in this group?

Answer 1

erythromycin

Question 2

What are the two drugs within the MACROLIDES AND AZALIDES group?

Answer 2

erythromycin and clindamycin

Question 3

What is a chemically an azalide derived from erythromycin?

Answer 3

azithromycin (Zithromax)

Question 4

What is the preferred and constitutes the vast majority of macrolide use?

Answer 4

azithromycin
Due to the drug interaction and side effect profiles of erythromycin and clarithromycin,

Question 5

Macrolides exhibit what kind of properties that help in their effectiveness in infections and cystic fibrosis?

Answer 5

exhibit immunomodulating properties

Question 6

What is the MOA of macrolides and azalides?

Answer 6

reversibly binds to the P site of the 50S ribosomal subunit of susceptible organisms and may inhibit RNA-dependent protein synthesis by stimulating the dissociation of peptidyl-tRNA from ribosomes.

Question 7

What activity do macrolides and azalides have?

Answer 7

Atypical and intracellular organisms commonly resistant to beta-lactam antibiotics

Question 8

What activity does Clarithromycin have?

Answer 8

greater activity than erythromycin or azithromycin against gram-positive organisms such as Streptococcus species and MSSA

Question 9

Best macrolide in treating H. influenzae?

Answer 9

Azithromycin

Question 10

How is resistance mediated for macrolides and azalides?

Answer 10

(1) reduced permeability of the cell membrane or active efflux,
(2) modification of the ribosomal binding site by chromosomal mutation, or
(3) production of esterase by Enterobacterales that hydrolyze macrolides.

Question 11

How are macrolides and azalides absorbed?

Answer 11

Well-absorbed from the duodenum following oral administration
Minimal absorption occurs after topical or ophthalmic use.

Question 12

How are macrolides and azalides distributed?

Answer 12

Distribute readily to body tissues and enter pleural fluid, ascitic fluid, middle-ear exudates, and sputum. When meninges are inflamed, macrolides enter the CSF.

Question 13

How are macrolides and azalides metabolized?

Answer 13

Partially metabolized by the liver, and clarithromycin is converted to active metabolites

Question 14

How are macrolides and azalides excreted?

Answer 14

Excreted mainly unchanged in bile; the drug is also excreted unchanged in urine in varying degrees

Question 15

Why does erythromycin have so many drug interactions?

Answer 15

Erythromycin is heavily metabolized by CYP3A4, which explains many of its drug interactions.

Question 16

Azithromycin needs to be given cautiously in which patients?

Answer 16

principally excreted via the liver. Patients with impaired hepatic function require cautious use of this drug

Question 17

What EKG changes must be monitored for macrolides and azalides use?

Answer 17

QT interval

Question 18

Erythromycin is contraindicated for patients with?

Answer 18

Preexisting liver disease

Question 19

Clindamycin dosing is dependent on?

Answer 19

Renal impairment with CrCl less than 30 mL/min, with or without hepatic impairment, requires that dosages be halved or the dosing interval doubled.

Question 20

Adverse reactions of macrolides and azalides

Answer 20

Dose-related GI symptoms. Liver abnormalities

Question 21

Why do Clarithromycin and erythromycin have the most drug interactions?

Answer 21

because they are strong inhibitors of the CYP enzymes, particularly CYP3A4.

Question 22

Clinical uses of erythromycin

Answer 22

Erythromycin ophthalmic ointment 0.5% is administered to all newborns to prevent ophthalmia neonatorum. Erythromycin is indicated in chlamydial conjunctivitis in newborns and chlamydial pneumonia in infants caused by C. trachomatis

Question 23

What is a major reason for selection of azithromycin over other drugs ?

Answer 23

the enhanced compliance caused by its convenient dosing schedule. However, with its once-daily dosing and short duration of 3 to 5 days, a single missed dose could jeopardize the successful outcome.