Exam 7: Tetracyclines and Macrolides Flashcards Preview

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Flashcards in Exam 7: Tetracyclines and Macrolides Deck (28)
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1
Q

What is the structure of tetracyclines?

A

4 rings…

2
Q

What shouldn’t you consume with Tetracyclines? Why?

A

Dairy products or antacids

They bind to Calcium, decreasing their absorption

3
Q

Which Tetracycline is preferred for IV administration? When is it used?

A

Doxycycline (long-acting Tetracycline)

Used for serious infections and when oral use causes GI upset.

4
Q

What precaution should you take when taking a Tetracycline? Why?

A

Drink with lots of water, standing up

They are prone to causing esophageal ulceration

5
Q

How are tetracyclines excreted? Exception?

A

By the kidneys through glomerular filtration
Also in the bile/feces
Doxycycline is excreted mostly non-renal mechanisms (useful for patients with renal failure)

6
Q

Tetracycline Mechanism

A

Inhibit bacterial protein synthesis by binding to the 30S Ribosomal Subunit, preventing addition of amino acids onto peptide chains
Enter the bacteria via passive diffusion and active transport
STATIC AGENTS

7
Q

Mechanisms of Resistance to Tetracyclines

A

Efflux pumps spit the drug out of the bacteria (gram negatives and Staph)
Tet(M) ribosomal protection protein in Gram positives
** Tetracyclines are a good marker for MDR because plasmids usually also have resistance genes for Aminoglycosides, Sulfonamides, and Chloramphenicol.

8
Q

Tetracycline Spectrum

A

Lots of resistance with Gram positives (staph/strep)
Pseudomonas and Enterobacteraceae are resistant.
Anaerobes tened to be resistant
Good against Atypical Bacteria (Spirochetes, Rickettsiae, Mycoplasma pneumo, Chlamydia)

9
Q

Uses of Tetracyclines

A

Rickettsial (RMSF) Doxycycline
Mycoplasma (atypical pneumonia) Doxycycline
Chlamydia (doxy)
Spirochetes/Lyme disease (doxy)
Periodontitis- useful because they are both antibacterial and are collagenase inhibitors** (doxy/minocycline)
Acne (doxy/tetra/minocycline)

10
Q

Tetracycline Adverse Effects

A

GI Upset, make sure to take with food
Superinfection (C diff)
** Can be deposited into growing teeth/bones because they bind to calcium. Cause teeth discoloration/enamel and bone deformities in babies when given to pregnant women.
When used past expiration date, they can cause renal damage
Photosensitivity
Can inhibit ADH and cause a DI-like state (could be used to treat SIADH)

11
Q

Tetracycline Contraindication ** Probably on test

A

Pregnant women and children under 8 years old

Calcium/tetracycline complexes get deposited into bones/teeth and cause tooth discoloration and bone/enamel deformities

12
Q

Tigecycline

A

Newer Tetracycline

Used in Skin/intraabdominal infections

13
Q

What is the tissue distribution of macrolides?

A

Most tissues, but DO NOT enter CSF

14
Q

Macrolide elimination mechanism

A

Metabolized by p450 system

No need to adjust dose for renal failure

15
Q

How can macrolide absorption be increased?

A

Enteric coating or esthrization improve oral absorption

16
Q

Macrolide Mechanism

A

Static usually, can be cidal
Bind to 50S subunit and prevent movement of polypeptide chains from the acceptor site to the donor site (block protein synthesis)

17
Q

Macrolide Resistance Mechanism

A

Modification of the 50S ribosomal subunit by methylase

Also Efflux pumps

18
Q

Erythromycin Spectrum

A

GAS, some other strep and staph, Corynebacterim

19
Q

Uses of Macrolides

A

Mycoplasma pneumonia (USE THE MACROLIDE IF THE PATIENT IS PREGNANT, NOT THE TETRACYCLINE*****)
Legionella
Community acquired pneumonia
Non strep pharyngitis (corynebacterium)
Chlamydia
Alternative to beta lactams when bacteria is resistant

20
Q

Adverse Effects of Macrolides

A

GI Upset due to direct GI motility stimulation (can be used to improve GI motility)

21
Q

Erythromycin Adverse Effect

A

Can inhibit p450 enzymes, messing with other drugs

Associated with sudden cardiac death when interacting with other medications

22
Q

Clarithromycin/Azithromycin General Features

A
Newer macrolide
Better oral absorption
Less GI intolerance
Longer half life
Clarithromycin inhibits P450 like erythromycin, but Azithromycin does not.
23
Q

Azithromycin Half life? Why?

A
3 days (very long)
It concentrates in the tissues and slowly releases over time
24
Q

Uses of Clarithromycin/Azithromycin

A

Mycobacterium Avium
Very good against H flu, especially Azithromycin
Azithromycin is highly effective against Chlamydia, also Gonorrhea at high doses
Respiratory and skin infections

25
Q

Azithromycin Consideration

A

May lead to deadly arrhythmias

Highest risk was in patients with preexisting heart problems

26
Q

Telithromycin

A

New Macrolide
Used for Community Acquired Pneumonia
Inhibits CYP 3A4 can cause liver toxicity

27
Q

How should you treat Gonorrhea?

A

First line- Ceftriaxone plus Azithromycin or Doxycycline
Second line- Cefixime + Azithromycin or Doxycycline
Make sure you treat for Chlamydia (co-infection is common)

28
Q

How should you treat Chlamydia?

A

Azithromycin (1 dose) or Doxycycline (7 days)