20 Questions
What is the primary mechanism of absorption for aminoglycosides?
Not absorbed orally, due to polar compounds
What is the primary mode of elimination for aminoglycosides?
Renal elimination
What is the percentage incidence of nephrotoxicity associated with aminoglycosides?
6-7%
What is the effect of concurrent administration of aminoglycosides with neuromuscular blockers?
Neuromuscular paralysis
What is the primary mechanism of antibacterial effect of aminoglycosides?
Bacteriostatic activity
What is the effect of aminoglycosides on myasthenia gravis patients?
Particularly at risk of neuromuscular paralysis
What is the mechanism of action of quinolone antibiotics?
Inhibition of nucleic acid synthesis
Which of the following antibiotics is an antimetabolite?
Sulfonamides
What is the clinical use of sulfonamide antibiotics?
Gram-negative rod infections
Which of the following antibiotics is often used in combination with penicillin G or ampicillin to treat enterococcal infections?
Gentamicin
How is vancomycin eliminated from the body?
Renal filtration
What is a common side effect of vancomycin?
Red man syndrome
Which of the following penicillins is sensitive to beta-lactamase and has a narrow spectrum?
Penicillin G
What is the primary mechanism of elimination for most penicillins?
Active tubular secretion
Which of the following bacteria is NOT typically covered by the spectrum of ampicillin?
MRSA
What is the primary purpose of beta-lactamase inhibitors?
To protect penicillins from inactivation by beta-lactamases
What is the most common side effect of penicillin therapy?
Hypersensitivity
Which of the following penicillins undergoes enterohepatic cycling?
Ampicillin
What is the primary characteristic of benzathine penicillin G?
It is a repository form with a long half-life
Which of the following statements is TRUE about the spectrum of ticarcillin?
It has increased activity against Pseudomonas aeruginosa
Study Notes
Vancomycin
- Spectrum: MRSA, Enterococci, Clostridium difficile (backup drug)
- Resistance: Vancomycin-resistant staphylococcal (VRSA) and enterococcal (VRE) strains
- Pharmacokinetics: used IV and orally (not absorbed) in colitis, enters most tissues, eliminated by renal filtration
- Side effects: "Red man syndrome" (histamine release), ototoxicity (permanent, additive with other drugs), nephrotoxicity (mild, additive with other drugs)
Aminoglycosides
- Mechanism of action: inhibition of protein synthesis
- Spectrum: gram-negative rods; gentamicin, tobramycin, and amikacin often used in combinations
- Pharmacokinetics: polar compounds, not absorbed orally, widely distributed into tissues, renal elimination proportional to GFR
- Side effects: nephrotoxicity (6-7% incidence), ototoxicity (2% incidence), neuromuscular paralysis
Beta-Lactams
- Subgroups:
- Narrow spectrum, beta-lactamase sensitive: penicillin G and penicillin V (spectrum: streptococci, pneumococci, meningococci, Treponema pallidum)
- Very narrow spectrum, beta-lactamase resistant: nafcillin, methicillin, oxacillin (spectrum: known or suspected staphylococci, not MRSA)
- Broad spectrum, beta-lactamase sensitive: ampicillin and amoxicillin (spectrum: gram-positive cocci, E. coli, H. influenzae, Listeria monocytogenes, Borrelia burgdorferi, H. pylori)
- Extended spectrum, antipseudomonal, beta-lactamase sensitive: ticarcillin, piperacillin (spectrum: increased activity against gram-negative rods, including P. aeruginosa)
- Pharmacokinetics: most eliminated via active tubular secretion, dose reduction needed only in major renal dysfunction
- Side effects: hypersensitivity (5-7% incidence), GI distress, Jarisch-Herxheimer reaction in treatment of syphilis
This quiz covers the pharmacokinetics and side effects of aminoglycosides, including their use in treating bacterial infections and tuberculosis.
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