Macrolides Overview Quiz

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Questions and Answers

What is the primary mechanism of action of macrolides?

Inhibit DNA synthesis

Bind to 50S ribosomal subunits (correct)

Inhibit folic acid synthesis

Inhibit cell wall synthesis

Which of the following statements about the pharmacokinetics of erythromycin is true?

It is primarily excreted unchanged in urine.

It is poorly absorbed when taken orally. (correct)

Erythromycin does not pass the placental barrier.

Erythromycin is not affected by gastric acidity.

Which of the following is NOT indicated for treatment with macrolides?

Chlamydia infections

Respiratory tract infections

Hypothyroidism (correct)

Acne vulgaris

Which of the following is a known adverse effect of erythromycin?

Cholestatic hepatitis Signup and view all the answers

Macrolides are generally effective against which type of bacteria?

Both Gram-positive cocci and bacilli Signup and view all the answers

Which drug is specifically mentioned as having less gut upset compared to erythromycin?

Clarithromycin Signup and view all the answers

What is the significance of macrolides being more active in alkaline medium?

They demonstrate increased antibiotic potency. Signup and view all the answers

Which macrolide is utilized as a prokinetic agent in diabetic gastroparesis?

Erythromycin Signup and view all the answers

What is the mechanism of action of tetracyclines?

Binding to 30S ribosomal subunit Signup and view all the answers

Which tetracycline is completely absorbed orally and not affected by food?

Doxycycline Signup and view all the answers

What adverse effect is associated with chloramphenicol in newborns?

Gray Baby Syndrome Signup and view all the answers

What significant effect do tetracyclines have on bone and teeth?

Precipitation with calcium Signup and view all the answers

Which of the following tetracyclines is effective in the treatment of urinary tract infections due to its renal excretion?

Oxytetracycline Signup and view all the answers

What is the primary reason tetracyclines are not commonly used despite having a broad spectrum?

Serious toxic effects Signup and view all the answers

How do tetracyclines affect drug clearance when administered with antacids or dairy products?

Decrease absorption and bioavailability Signup and view all the answers

What precaution should be taken when administering tetracyclines to breastfeeding individuals?

Avoid use due to excretion in breast milk Signup and view all the answers

What is the mechanism of action for Clindamycin and Lincomycin?

Inhibits protein synthesis by binding to the 50S ribosomal subunit Signup and view all the answers

Which of the following statements regarding the pharmacokinetics of Clindamycin is true?

Highly concentrated in teeth and bone Signup and view all the answers

What is one of the primary clinical indications for Chloramphenicol?

Treatment of acute typhoid fever Signup and view all the answers

Which adverse effect is associated with Chloramphenicol?

Bone marrow depression Signup and view all the answers

What is the spectrum of activity for Clindamycin?

Effective against Gram-positive, Gram-negative, and anaerobes, except Clostridium difficile Signup and view all the answers

Which of the following is NOT a common indication for the use of Clindamycin?

Viral infections Signup and view all the answers

What is the main adverse effect of Clindamycin that could lead to serious complications?

Pseudomembranous colitis Signup and view all the answers

What type of infections is Chloramphenicol primarily effective against?

Respiratory tract infections and Rickettsial infections Signup and view all the answers

Which of the following antibiotics acts as an HME inhibitor, similar to erythromycin and clarithromycin?

None of the above Signup and view all the answers

Study Notes

Macrolides

Types: Erythromycin, clarithromycin, azithromycin, Roxithromycin, Olendamycin, Spiramycin
Erythromycin Source: Natural
Absorption: Absorbed orally but destroyed by stomach acid, given enteric-coated. IV administration is also possible.
Blood-Brain Barrier (BBB) Penetration: Poor penetration
Placental Barrier: Crosses the placental barrier, safe for use in pregnancy
Metabolism: Metabolized in the liver
Excretion: Excreted in urine and bile
Mechanism of Action: Binds reversibly to 50S ribosomal subunits, inhibiting protein synthesis translocation. More active in alkaline environments.
Bactericidal/Bacteriostatic Action: Bacteriostatic or bactericidal, depending on concentration
Spectrum: Effective against Gram-positive cocci and bacilli, some Gram-negative cocci and bacilli (e.g., H. influenza)

Clarithromycin

Compared to Erythromycin: More active against atypical bacteria, better oral absorption, less stomach upset
Uses: Peptic ulcer treatment (eradicate H. pylori)
Mechanism of Action (similar to erythromycin)

Azithromycin

Compared to Erythromycin: More active against mycobacteria and Chlamydia, less active against Staphylococcus and Streptococcus
Tissue Concentration: High tissue concentration; slow release from tissues
Administration: Given once daily
Mechanism of Action (similar to erythromycin)

Ketolides (Telithromycin)

Type: Semi-synthetic macrolide
Administration: Given orally once daily, high tissue concentration
Spectrum: Active against Gram-positive, Gram-negative bacteria, and Chlamydia
Mechanism of Action (similar to erythromycin)
Uses: Useful in cases of bacterial resistance to macrolides

Lincosamides (Clindamycin & Lincomycin)

Absorption: Absorbed orally and intravenously (IV). High concentration in bone and teeth.
Metabolism: Metabolized by the liver, excreted in urine and bile
Mechanism of Action: Similar to macrolides
Spectrum: Similar to macrolides, but more active against anaerobes, except Clostridium difficile
Indications: Treatment of anaerobic infections, prophylaxis against endocarditis, treatment of intra-abdominal/female genital infections
Adverse Effects: Superinfection by Clostridium difficile (pseudomembranous colitis), gastrointestinal disturbances, liver dysfunction

Broad-Spectrum Antibiotics: Chloramphenicol

Source: Natural
Absorption: Well absorbed orally, inject or topical. Passes BBB.
Metabolism: Metabolized by liver. Excreted primarily in urine.
Mechanism of Action: Binds to 50S ribosomal subunit, inhibits peptidyl transferase leading to protein synthesis inhibition.
Spectrum: Effective against Gram-positive, Gram-negative bacteria, rickettsia, and anaerobes.
Indications: Respiratory tract infections, typhoid fever, meningitis, rickettsial infections, anaerobic infections and topical use (eye/ear).
Adverse Effects: Bone marrow depression (e.g., agranulocytosis).

Tetracyclines

Source: Natural and semi-synthetic
Absorption: Variable, many are incompletely absorbed with food. Doxycycline unaffected by food.
Chelation: Forms complexes with divalent cations (Ca2+, Mg2+, Al3+), reduces absorption.
Distribution: Poor penetration of BBB, except minocycline. High bone, tooth, and calcified tissue concentration.
Excretion: Primarily excreted via urine.
Mechanism of Action: Binds 30S ribosomal subunit, inhibits protein synthesis
Spectrum: Broad spectrum; gram positives and negatives, chlamydia, rickettsia, spirochetes, and amoeba (luminal)
Indications: Variety of infections (respiratory, urinary, GI, other)
Adverse Effects:
- Toxic effects
- Gastrointestinal disturbances
- Superinfections
- Caries
- Photosensitivity
- Teratogenicity
- Other toxicities (hepatotoxicity,Fanconi syndrome,nephrotoxicity, CNS disturbances);

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Description

Test your knowledge on macrolides, including types like erythromycin and clarithromycin. Learn about their absorption, metabolism, and spectrum of activity. This quiz will help you understand key pharmacological details of these antibiotics.