39 Questions
Which tetracyclines achieve therapeutic levels in the cerebrospinal fluid?
Doxycycline and minocycline
What is the primary route of elimination for doxycycline?
Bile into the feces
Which of the following body fluids has inadequate penetration of tetracyclines?
Cerebrospinal fluid
What is the reason for noncompliance with tetracyclines?
Epigastric distress
Which of the following is a unique characteristic of minocycline?
High concentrations in saliva and tears
Why is doxycycline preferred in patients with renal dysfunction?
It is primarily eliminated via the bile into the feces
What is the reason behind the toxic effects of high concentrations of chloramphenicol or tetracyclines?
Interaction with mitochondrial mammalian ribosomes
What is the unique feature of the transport mechanism of tetracyclines in susceptible organisms?
Energy-dependent transport protein mechanism
Where do tetracyclines concentrate in susceptible organisms?
Intracellularly
What is the mechanism of action of tetracyclines in inhibiting protein synthesis?
Preventing binding of tRNA to the mRNA-ribosome complex
What is the characteristic feature of the structure of tetracyclines?
Four fused rings with a system of conjugated double bonds
What is the effect of substitutions on the rings of tetracyclines?
Alters the individual pharmacokinetics and spectrum of antimicrobial activity
What percentage of parenteral aminoglycosides are excreted unchanged in the urine?
More than 90%
In which bodily fluids do aminoglycosides penetrate variably?
Most body fluids
What is the primary route of excretion for neomycin?
Feces
Why is therapeutic drug monitoring necessary for aminoglycosides?
To minimize dose-related toxicities
What is the primary risk factor for ototoxicity and nephrotoxicity?
Age
Where do aminoglycosides accumulate in the inner ear?
Endolymph and perilymph
Where are erythromycin and its metabolites excreted?
Bile
What is the most common adverse effect of macrolides?
Gastric distress and motility
Why should the dosage of clarithromycin be adjusted in some patients?
In patients with renal impairment
What is a rare effect of high doses of erythromycin?
Smooth muscle contractions
Which macrolide is associated with irreversible sensorineural hearing loss?
Azithromycin
What is the excretion pathway of clarithromycin and its metabolites?
Urine through the kidneys
What is the mechanism of anemia associated with glucose-6-phosphate dehydrogenase deficiency?
Hemolytic anemia
Why are neonates more susceptible to the adverse effects of chloramphenicol?
They have underdeveloped renal function
What is the effect of chloramphenicol on the metabolism of warfarin and phenytoin?
It decreases their metabolism
What is the mechanism of action of clindamycin?
Similar to that of macrolides
What type of organisms is clindamycin primarily used to treat?
Gram-positive bacteria
What is the relationship between clindamycin and erythromycin resistance?
Cross-resistance has been described
What is the primary site of metabolism for quinupristin and dalfopristin?
Liver
What is the result of quinupristin/dalfopristin's competition with the antibiotic for excretion?
Hyperbilirubinemia
What is the mechanism of action of oxazolidinones?
Binding to the bacterial 23S ribosomal RNA
What is the antibacterial spectrum of oxazolidinones primarily directed against?
Gram-positive organisms
What is the effect of quinupristin/dalfopristin on cytochrome P450 CYP3A4 isoenzyme?
Inhibits cytochrome P450 CYP3A4 isoenzyme
What is the primary excretion pathway of quinupristin and dalfopristin?
Feces
What is the result of administering quinupristin/dalfopristin through a peripheral rather than a central line?
Venous irritation
What is the effect of higher doses of quinupristin/dalfopristin?
Arthralgia and myalgia
What is the antibacterial activity of oxazolidinones against Mycobacterium tuberculosis?
Moderately active
Learn about the types of protein synthesis inhibitors, including chloramphenicol and tetracyclines, and their effects on bacterial and mammalian ribosomes. Understand the mechanisms of action and potential toxic effects of these antimicrobial agents.
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