Macrolides, Clindamycin, Tetracycline

Question 1

Macrolide
- Resistance Mechanism

Answer 1

1. Active Efflux
2. Ribosomal Methylation
3. Alteration of 50S RIbosomal Subunit
4. Enzyme Inactivation
5. Decreased permeability of cell wall

Question 2

Macrolides
- Adverse Effects

Answer 2

• GI
• Fetal Abnormalities (Clarithromycin)
• Increased QTC (Eryth > Clair > Azith)

Question 3

Macrolides
- Azithromycin vs Erythromycin vs Clarithromycin

Answer 3

Azithromycin has less drug interactions (CYP 3A4)

Azithromycin appears safe in pregnancy

Question 4

Macrolide
- Counseling

Answer 4

CYP 3A4 interactions (Exception: Azithromycin)

May take with food

Question 5

Clindamycin
- Resistance Mechanisms

Answer 5

1. Alteration of 50S ribosomal receptors
2. Alteration of 23S Ribosomal RNA of 50S ribosomal subunit
3. Enzyme inactivation
4. Intrinsic Resistance

Question 6

Clindamycin
- Adverse Effects

Answer 6

GI

Hepatotoxic

Question 7

Clindamycin
- Counseling

Answer 7

Not reduced by food

May decrease cyclosporine and macrolides

May enhance neuromuscular blocking agents

Question 8

Tetracycline
- Resistance Mechanisms

Answer 8

Decreased accumulation of drug
- Decreased influx
- Increased efflux

Resistance is transmitted via plasmid

Tigecycline: Has no resistance yet

Question 9

Tetracycline
- Adverse Effects

Answer 9

• Photosensitivity
• Hepatic / Renal toxicity

Question 10

Tetracycline
- Counseling

Answer 10

Absorption is reduced with dairy and cations (Doxy and Mino are reduced less)

Take with full glass of water in upright position

Avoid in pregnancy

Avoid in children younger than 8 unless no other alternatives