Macrolides

Question 1

MOA

macrolides

Answer 1

reversibly binds to the 50 S ribosomal subunit of bacteria – decrease protein synthesis

bacteriostatic

Question 2

Mechanism of resistance

macrolides

Answer 2

• dec permeability of the cell envelope
• altered 50 S ribosomal receptor site
• enzymatic inactivation of erythromycin by esterases

Question 3

Absorption of erythromycin

Answer 3

inactivated by gastric acid

better in fasting state

Question 4

Which erythromycin is not affected by food?

Answer 4

Emycin Estolate

Question 5

Distributes in ______ longer than in _____.

what is the resulting effect?

macrolides

Answer 5

tissue longer than in blood

very high conc in alveolar macrophages and leukocytes compared to extracellular fluids

Question 6

primary route of excretion of erythromycin

Answer 6

biliary excretion

only small % in urine

Question 7

How is erythromycin metabolized (inactivated) in the liver?

Answer 7

Demethylation

Question 8

Where and how is Clarithromycin metabolized?

Answer 8

liver
oxidation and hydrolysis

20-30% drug excreted into the urine unchanged

Question 9

Metabolism/excretion of Azithromycin?

Answer 9

small portion metabolized

Biliary excretion mainly

long half life (68 hrs)

Question 10

What allows for the 5 day regimen of Azithromycin?

Answer 10

long half life (68 hrs) which is consistent with a slow release of drug from tissues

Question 11

What are some ADR for Erythromycin?

Answer 11

• GI - cramps, N/V/D
• Thrombophelbitis
• Allergic rx
• Cholestatic hpatitis
• Ototoxicity, QT prolongation

Question 12

What can lead to cholestatic hepatitis?

Answer 12

Estolate preperation - adults and pregnant patients

Question 13

ADR for Clarithromycin/Azithromycin

Answer 13

GI, HA, Dizziness, Allergic rxn

Question 14

How do the three drugs affect p-450 enzymes?

macrolides

Answer 14

Erythromycin/Clarithromycin metabolites form inactive complexes with p-450 enzymes –> decreased metabolism of theophylline, warfarin, carbamazepine, cyclosporine

Azithromycin does not inactivate p-450 enzymes

Question 15

Spectrum of activity - how is Clarithromycin/Azithromycin different from Erythromycin?

Answer 15

All:
Gram pos - staph and strep
Atypicals

Clarith/Azith:
H. flu, M. Cat

Question 16

Uses

macrolides

Answer 16

PCN allergic patients
CAP (only Cl/Az)
Mycoplasma pneumoniae
Legionnaire's disease 
Chlamydia trachomatis nongonococcal urethritis and cervicitis (not the estolate form during pregnancy)