Macrolides

Question 1

What are the 3 Macrolides?

Answer 1

Erythromycin (E-mycin)
Clarithromycin (Biaxin)
Azithromycin (Zithromax)

Question 2

Are Macrolides Bacteriocidal or Bacteriostatic?

Answer 2

BACTERIOSTATIC

Question 3

What is the Mcarolide mechanism of action?

Answer 3

REVERSIBLY binds to the 50S-ribosomal subunit of bacteria to decrease protein synthesis.

Question 4

What 3 methods to bacteria use to gain resistance against Macrolides?

Answer 4

• Decreased permeability of the cell envelope
• Alter 50S ribosomal subunit
• Enzymatic inactivation of erythromycin by esterases

Question 5

Why is Erythromycin often enterically coated?

Answer 5

Rapidly inactivated by gastric acid

Question 6

Why is stomach irritation often an adverse effect of taking Erythromycin?

Answer 6

Taken on empty stomach because absorbed better when fasting

(however E-mycin Estolate not affected by food.

Question 7

Compare Macrolide tissue distribution to blood.

Where do Macrolides accumulate the best?

Answer 7

Tissues > Blood

Lungs and Leukocytes most

Question 8

Why is there a problem with resistance development and macrolide usage?

Answer 8

Long half lives leaves residual amounts of drug in tissue long after terapy completed

Question 9

Describe excretion of each of the Macrollides.

Answer 9

Erythromycin: biliary excretion mostly as hepatically inactivated metabolite

Clarithromycin: biliary excretion with 20% renal excretion

Azithromycin: biliary excretion as active drug

Question 10

What adverse side effects are associated with Erythromycin?

Answer 10

• abdominal cramps, N/V/D
• Thrombophelbitis (IV)
• Cholestatic hepatitis (rare) with Estolate preparation in adults and pregnant women
• Ototoxicity, QT prolongation (rare)

Question 11

What adverse side effects of Erythromycin is associated with large doses?

Answer 11

Ototoxicity, QT prolongation

Question 12

What adverse side effects of Erythromycin is associated with Estolate form and pregnant women and adults (why you shouldn’t give E-mycin Estolate to pregnant women)?

Answer 12

Cholestatic hepatitis

Question 13

Why is Erythromycin often given to patients who have gastroparesis (specially in diabetic gastroparesis)?

Answer 13

E-mycin stimulates motilin receptors, resulting in gastromobility

Question 14

Which Macrolide leaves a strong metallic taste in patients’ mouths after taking it?

Answer 14

Clarithromycin

Question 15

What adverse side effects are associated with Clarithromycin and Azithromycin?

Answer 15

• GI - not as severe as erythromycin
• Headache
• Dizziness
• Allergic reactions

Question 16

Why do Erythromycin and Clarithromycin slow metabolism of Theophylline, Warfarin, Carbamazepine, & Cyclosporine?

Answer 16

Their metabolites form inactive complexes with p- 450 enzymes

Question 17

What affect does Azithromycin have on Cytochrome P450s?

Answer 17

NONE

Question 18

What bugs are covered by Macrolides?

Answer 18

Staph
Strep

Atypicals

H. Pylori (Clarithromycin)

H. Flu (Clarithromycin, Azithromycin)
M. Cat (Clarithromycin, Azithromycin)
Mycobacterium Avium Complex (Clarithromycin, Azithromycin)

Question 19

What bugs are covered by all Macrolides?

Answer 19

Staph
Strep

Chlamydia
Mycoplasma
Legionella

Question 20

What bugs are covered by Clarithromycin and Azithromycin but not Erythromycin?

Answer 20

H. Flu (Clarithromycin, Azithromycin)
M. Cat (Clarithromycin, Azithromycin)
Mycobacterium Avium Complex (Clarithromycin, Azithromycin)

Question 21

What bug is covered by Clarithromycin but not any other Macrolide (hint ulcers)?

Answer 21

H. Pylori

Question 22

Why is it bad to treat Chlamydia infections during pregnancy with an estolate form of a macrolide?

Answer 22

Cholestatic hepatitis

Question 23

What ABX would you use to treat a patient with walking pneumonia?

With Legionaire’s Disease?

Answer 23

any Macrolide

any Macrolide