Pharmacology Quiz: Macrolides & Glycopeptide Antibiotics

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Questions and Answers

What is the primary route of excretion for erythromycin and azithromycin?

Lungs

Kidneys

Bile (correct)

Liver

How does food affect the absorption of erythromycin and azithromycin?

Variable effect

Decreases absorption (correct)

No effect

Increases absorption

What is the half-life of azithromycin?

6-8 hours

1-1.5 hours

40-60 hours (correct)

12-24 hours

What percentage of azithromycin is bound to proteins?

12-50% Signup and view all the answers

What is a characteristic of azithromycin's tissue penetration?

High penetration, especially in infected tissue Signup and view all the answers

What is a characteristic of erythromycin's microsomal enzyme inhibition?

High inhibition Signup and view all the answers

What is a characteristic of azithromycin's spectrum of activity?

Broader spectrum, including gram-negative bacteria and chlamydia Signup and view all the answers

What is a characteristic of erythromycin's gastric acid stability?

Requires enteric coating Signup and view all the answers

Which of the following is true about the spectrum of activity of erythromycin?

More active against gram-positive bacteria Signup and view all the answers

Which of the following are considered macrolide antibiotics?

Clarithromycin Signup and view all the answers

What is the primary mechanism of action of macrolides?

Inhibiting RNA-dependent protein synthesis Signup and view all the answers

At therapeutic doses, macrolides are primarily known for which effect?

Bacteriostatic Signup and view all the answers

Which of the following infections can be treated with erythromycin?

Syphilis Signup and view all the answers

Which bacterium is treated with azithromycin?

Streptococcus pneumoniae Signup and view all the answers

In which situation is erythromycin commonly used?

In patients allergic to penicillin Signup and view all the answers

What is a common bacterial infection treated with clarithromycin?

Pertussis Signup and view all the answers

What is a common side effect of motilin activation?

Nausea Signup and view all the answers

Which form of erythromycin is most likely to cause cholestatic jaundice?

Estolate form Signup and view all the answers

Which macrolide antibiotic was first isolated in 1952?

Erythromycin Signup and view all the answers

What effect do higher doses of macrolides have on bacteria?

They may be bactericidal Signup and view all the answers

Which of the following is NOT a common hypersensitivity reaction to erythromycin estolate?

Diarrhea Signup and view all the answers

What cardiac side effect is erythromycin known to be associated with?

QT prolongation Signup and view all the answers

How does azithromycin compare to erythromycin in terms of spectrum of activity?

Azithromycin has a broader spectrum Signup and view all the answers

What is the role of antitoxin in infections caused by Corynebacterium diphtheriae?

To prevent the establishment of carriers Signup and view all the answers

What does the term "cross-resistance" mean in the context of azithromycin and erythromycin?

Bacteria resistant to one drug are likely resistant to the other Signup and view all the answers

Which condition is Azithromycin the drug of choice for?

Non-gonococcal urethritis caused by Chlamydia trachomatis Signup and view all the answers

Which of these statements is TRUE regarding motilin activation?

It can cause abdominal discomfort and diarrhea Signup and view all the answers

Which antibiotic is indicated for the treatment of community-acquired pneumonia of mild severity?

Clarithromycin Signup and view all the answers

Which of these is a side effect specifically associated with the estolate form of erythromycin?

Cholestatic jaundice Signup and view all the answers

What type of distress is an adverse effect of erythromycin?

Epigastric distress Signup and view all the answers

Which statement accurately describes the relationship between azithromycin and erythromycin?

Azithromycin is a synthetic derivative of erythromycin Signup and view all the answers

Which adverse effect of erythromycin is due to motilin-receptor agonism?

Epigastric distress Signup and view all the answers

What condition is not treated by Azithromycin?

Acute bacterial exacerbation of chronic obstructive pulmonary disease Signup and view all the answers

Which of the following is a use for Clarithromycin?

Acute maxillary sinusitis due to Haemophilus influenzae Signup and view all the answers

Which pathogen is associated with acute otitis media treated by Clarithromycin?

Haemophilus influenzae Signup and view all the answers

Which of the following is not an indication for Azithromycin?

Acute bacterial exacerbation of chronic obstructive pulmonary disease Signup and view all the answers

What is the primary mechanism of action of vancomycin and teicoplanin?

Inhibition of cell wall synthesis Signup and view all the answers

Which part of the bacterial cell wall do vancomycin and teicoplanin bind to?

D-alanyl-D-alanine Signup and view all the answers

What is the primary effect of vancomycin and teicoplanin binding to the bacterial cell wall?

Formation of an imperfect cell wall Signup and view all the answers

Why are vancomycin and teicoplanin ineffective against Gram-negative bacteria?

They are not able to penetrate the outer membrane Signup and view all the answers

Which of the following is NOT a characteristic of vancomycin and teicoplanin?

Effective against Gram-negative bacteria Signup and view all the answers

What is the primary reason for the bactericidal action of vancomycin and teicoplanin?

Inhibition of cell wall synthesis leading to cell lysis Signup and view all the answers

What is a potential consequence of an imperfect cell wall in bacteria treated with vancomycin or teicoplanin?

Entry of fluid into the bacteria Signup and view all the answers

What is the most likely reason for the limited effectiveness of vancomycin and teicoplanin against Gram-negative bacteria?

Their inability to penetrate the outer membrane Signup and view all the answers

Which of the following best describes the mechanism of action of vancomycin and teicoplanin?

Inhibiting the synthesis of the bacterial cell wall Signup and view all the answers

Study Notes

Macrolides

Commonly used family of antibiotics, with erythromycin as the first member isolated in 1952 from Streptomyces erythreus.
Key macrolides include erythromycin, clarithromycin, azithromycin, and roxithromycin.

Mechanism of Action

Macrolides inhibit RNA-dependent protein synthesis by binding to the 'P' site on the 50S ribosomal subunits.
This binding disrupts peptidyl tRNA dissociation, suppressing protein synthesis and inhibiting bacterial growth.
They are generally bacteriostatic at therapeutic doses but can be bactericidal at higher doses.

Therapeutic Uses

Erythromycin:
- Effective for penicillin-allergic patients and prophylaxis against bacterial endocarditis.
- Treats respiratory tract infections caused by Streptococcus pyogenes and pneumoniae, Mycoplasma pneumoniae, and pertussis.
- Used in diphtheria cases as an adjunct to antitoxin.
Azithromycin:
- Treats acute bacterial exacerbations in chronic obstructive pulmonary disease.
- Effective for community-acquired pneumonia and streptococcal pharyngitis/tonsillitis.
- Drug of choice for non-gonococcal urethritis and cervicitis.
Clarithromycin:
- Indicated for pharyngitis, acute maxillary sinusitis, bacterial bronchitis exacerbations, and otitis media.
- Useful for community-acquired pneumonia due to multiple pathogens.

Adverse Effects of Erythromycin

Epigastric distress: Degraded to a hemiketal intermediate causing gastrointestinal contractions, leading to discomfort, nausea, and diarrhea.
Cholestatic jaundice: Associated with the estolate form, likely due to hypersensitivity.
Hypersensitivity reactions: May present as skin rashes, fever, and eosinophilia.
Cardiac side effects: Can prolong QT interval and cause ventricular arrhythmias, including torsades de pointes.

Comparison: Erythromycin vs. Azithromycin

Azithromycin: Semisynthetic derivative with broader activity and cross-resistance with erythromycin.
Food absorption: Both affected; erythromycin requires enteric coating for stability.
Half-life: Erythromycin (1-1.5 hours) vs. Azithromycin (40-60 hours).
Protein binding: Erythromycin (70%) vs. Azithromycin (12-50%).
Tissue penetration: Erythromycin has poor penetration; azithromycin shows high penetration, especially in infected tissues.
Spectrum of activity: Erythromycin is more effective against gram-positive bacteria, while azithromycin includes gram-negative bacteria and chlamydia.

Glycopeptide Antibiotics

Vancomycin & Teicoplanin Mechanism of Action:
- Both are bactericidal, inhibiting cell wall synthesis.
- Bind to D-alanyl-D-alanine in peptidoglycan, preventing elongation and cross-linking.
- Leads to formation of an imperfect cell wall, causing cell swelling and bursting.
- Alters cytoplasmic membrane permeability but is ineffective against gram-negative organisms due to larger size.

Uses and Adverse Effects of Vancomycin

Vancomycin is administered intravenously for various bacterial infections.
Adverse effects include nephrotoxicity, ototoxicity, and infusion-related reactions (Red Man syndrome).

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Description

This quiz covers macrolides, a family of antibiotics, including their discovery, derivatives, and types. It also touches on glycopeptide antibiotics.