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Questions and Answers
What is the mechanism of action of macrolides in inhibiting protein synthesis?
What is the mechanism of action of macrolides in inhibiting protein synthesis?
- Inhibiting tRNA synthesis
- Stimulating peptidyl tRNA synthesis
- Binding to the 30s ribosomal subunit
- Reversibly binding to the 50s ribosomal subunit (correct)
Which macrolide has a similar antimicrobial spectrum as erythromycin but is more effective against certain gram-negative bacteria?
Which macrolide has a similar antimicrobial spectrum as erythromycin but is more effective against certain gram-negative bacteria?
- Azithromycin
- Roxithromycin (correct)
- Clarithromycin
- Telithromycin
What is the primary site of metabolism for erythromycin?
What is the primary site of metabolism for erythromycin?
- Liver (correct)
- Kidneys
- Lungs
- Intestines
Which statement best describes the pharmacokinetics of macrolides?
Which statement best describes the pharmacokinetics of macrolides?
What effect does macrolide binding have on the ribosome?
What effect does macrolide binding have on the ribosome?
What is the half-life (t½) of erythromycin?
What is the half-life (t½) of erythromycin?
What is the primary route of excretion for erythromycin?
What is the primary route of excretion for erythromycin?
Which enzyme does erythromycin strongly inhibit?
Which enzyme does erythromycin strongly inhibit?
What are some of the potential life-threatening drug interactions associated with erythromycin?
What are some of the potential life-threatening drug interactions associated with erythromycin?
What percentage of patients may experience gastrointestinal adverse effects from erythromycin?
What percentage of patients may experience gastrointestinal adverse effects from erythromycin?
In which patients is hepatic cholestatic toxicity from erythromycin more common?
In which patients is hepatic cholestatic toxicity from erythromycin more common?
Which macrolide antibiotic has a longer half-life compared to erythromycin?
Which macrolide antibiotic has a longer half-life compared to erythromycin?
Which macrolide antibiotic is extraordinarily well-tolerated and has very few drug interactions?
Which macrolide antibiotic is extraordinarily well-tolerated and has very few drug interactions?
Which mechanism of antibiotic resistance involves methylation of the 23s rRNA of the 50s ribosomal subunit?
Which mechanism of antibiotic resistance involves methylation of the 23s rRNA of the 50s ribosomal subunit?
Which resistance mechanism for macrolides is associated with enzymatic inactivation of erythromycin by esterases or phosphotransferases?
Which resistance mechanism for macrolides is associated with enzymatic inactivation of erythromycin by esterases or phosphotransferases?
What types of microorganisms belong to the Gram-negative group that shows primary resistance to macrolides due to decreased permeability?
What types of microorganisms belong to the Gram-negative group that shows primary resistance to macrolides due to decreased permeability?
Which bacterial protein synthesis inhibitor reversibly binds to the 50s ribosomal subunit and interferes with the elongation phase?
Which bacterial protein synthesis inhibitor reversibly binds to the 50s ribosomal subunit and interferes with the elongation phase?
What is a general characteristic of erythromycin's metabolism?
What is a general characteristic of erythromycin's metabolism?
Which macrolide antibiotic has a similar antimicrobial spectrum as erythromycin and is more effective against certain gram-negative bacteria?
Which macrolide antibiotic has a similar antimicrobial spectrum as erythromycin and is more effective against certain gram-negative bacteria?
What is the primary route of excretion for erythromycin?
What is the primary route of excretion for erythromycin?
Which resistance mechanism for macrolides is associated with enzymatic inactivation of erythromycin by esterases or phosphotransferases?
Which resistance mechanism for macrolides is associated with enzymatic inactivation of erythromycin by esterases or phosphotransferases?
What effect does macrolide binding have on the ribosome?
What effect does macrolide binding have on the ribosome?
What is the mechanism of action of azithromycin in inhibiting protein synthesis?
What is the mechanism of action of azithromycin in inhibiting protein synthesis?
What factor contributes to macrolide resistance among most Gram-negative bacteria?
What factor contributes to macrolide resistance among most Gram-negative bacteria?
Which macrolide antibiotic is most likely to inhibit cytochrome P450 enzymes?
Which macrolide antibiotic is most likely to inhibit cytochrome P450 enzymes?
What adverse effect is more common with higher doses of clarithromycin?
What adverse effect is more common with higher doses of clarithromycin?
Which antibiotic has a longer half-life compared to azithromycin?
Which antibiotic has a longer half-life compared to azithromycin?
What is the primary route of excretion for azithromycin?
What is the primary route of excretion for azithromycin?
Which macrolide antibiotic is associated with lifethreatening drug interactions such as with midazolam, quinidine, and warfarin?
Which macrolide antibiotic is associated with lifethreatening drug interactions such as with midazolam, quinidine, and warfarin?
What is the primary site of metabolism for clarithromycin?
What is the primary site of metabolism for clarithromycin?
What percentage of patients may experience gastrointestinal adverse effects from azithromycin?
What percentage of patients may experience gastrointestinal adverse effects from azithromycin?
In which patients is hepatic cholestatic toxicity from erythromycin more common?
In which patients is hepatic cholestatic toxicity from erythromycin more common?
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Study Notes
Mechanism of Action
- Macrolides inhibit protein synthesis by binding to the 50s ribosomal subunit, interfering with the elongation phase.
Azithromycin
- Has a similar antimicrobial spectrum as erythromycin but is more effective against certain gram-negative bacteria.
- Has a longer half-life compared to erythromycin.
Erythromycin
- Primary site of metabolism is in the liver.
- Half-life (t½) is 1.5-2 hours.
- Primary route of excretion is through the bile.
- Strongly inhibits cytochrome P450 enzymes.
- Can cause gastrointestinal adverse effects in up to 30% of patients.
- Hepatic cholestatic toxicity is more common in elderly patients.
Macrolide Resistance
- Can occur through methylation of the 23s rRNA of the 50s ribosomal subunit.
- Can occur through enzymatic inactivation of erythromycin by esterases or phosphotransferases.
- Decreased permeability contributes to primary resistance in Gram-negative bacteria.
Clarithromycin
- Has a longer half-life compared to azithromycin.
- Is associated with life-threatening drug interactions such as with midazolam, quinidine, and warfarin.
- Primary site of metabolism is in the liver.
- Higher doses can cause gastrointestinal adverse effects.
- Can cause hepatic cholestatic toxicity, more common in elderly patients.
Pharmacokinetics
- Macrolides have a narrow therapeutic window and are metabolized in the liver.
Ribosome Binding
- Macrolide binding causes a conformational change in the ribosome, blocking the exit tunnel and inhibiting protein synthesis.
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