24 Questions
What is the mechanism of action of Vancomycin?
Inhibition of cell wall synthesis
Which of the following antibiotics is effective against Gram +ve and -ve organisms and anaerobes?
Imipenem
What is the main advantage of Meropenem over Imipenem?
Less renal degradation
Why is cilastatin often given with Imipenem?
To inhibit its renal metabolism
What is the main indication for the use of Vancomycin?
MRSA infections
Which of the following antibiotics is considered safe in patients with a history of hypersensitivity to penicillin?
Aztreonam
What is the advantage of Ertapenem over Imipenem?
Less risk of convulsions
What is the purpose of combining clavulanic acid with amoxicillin in Augmentin?
To irreversibly inhibit β-lactamase
What is the main side effect of Imipenem?
All of the above
Which of the following is NOT a combination of a β-lactam antibiotic with a β-lactamase inhibitor?
Cefoperazone + tazobactam
What is the mechanism by which probenecid increases the duration of action of penicillin?
By inhibiting the renal tubular secretion of penicillin
What is the primary mechanism of hypersensitivity reactions to penicillin?
Immune reaction to penicilloic acid
Which of the following routes of administration is dependent on the stability of the antibiotic to gastric acidity?
Oral
What is the primary mechanism of action of β-lactam antibiotics?
Inhibition of cell wall formation
Which of the following is a characteristic of depot IM preparations of penicillin?
Slow absorption into the circulation
What is the primary site of excretion of penicillin?
Kidneys
What is the primary goal of antimicrobial therapy after a pathogen is cultured?
To choose an antimicrobial based on the pathogen's susceptibility
What is the difference between bactericidal and bacteriostatic antimicrobial drugs?
Bactericidal drugs kill the organism, while bacteriostatic drugs stop the growth of the organism
What is the classification of antimicrobial drugs based on their effect on bacteria?
Bactericidal vs. bacteriostatic
What is the primary consideration for choosing an antimicrobial agent?
The site of infection
What is the significance of the minimum inhibitory concentration (MIC) in antimicrobial therapy?
It is the concentration of the antimicrobial that inhibits the growth of the pathogen
What is the primary mechanism of action of cell wall inhibitors?
Inhibition of cell wall formation
What is the classification of antimicrobial drugs based on their spectrum of activity?
Narrow spectrum vs. extended spectrum
What is the primary consideration for dosing of β-lactam antibiotics in patients with impaired renal function?
Dose adjustment based on the patient's renal function
Study Notes
Irreversible Inhibitors of β-Lactamase
- Combine with β-lactam antibiotics to protect against β-lactamase-producing organisms
- Examples:
- Amoxicillin + clavulanic acid (Augmentin)
- Ampicillin + sulbactam (Unasyn) (IV)
- Ticarcillin + clavulanic acid (Timentin) (IV)
- Piperacillin + tazobactam (Zosyn) (IV)
- Cefoperazone + sulbactam (Sulperazone)
Pharmacokinetics of Penicillins
- Absorption: oral, IV, or IM, depending on stability to gastric acidity and severity of infection
- Depot IM preparations: procaine penicillin G and benzathine penicillin G
- Can cross the placenta, but are not teratogenic
- Can cross the blood-brain barrier (BBB) in inflamed meninges (e.g., meningitis)
- Excretion: primarily renal, with probenecid inhibiting renal tubular secretion
- Distribution: bone, with low levels persisting over a long time period
Adverse Effects of Penicillins
- Hypersensitivity:
- Most important adverse effect
- Caused by penicilloic acid, a metabolite that reacts with proteins and serves as a hapten
- May cause rashes, angioedema, and anaphylaxis
- Allergic cross-sensitivity may occur between penicillins and 1st-generation cephalosporins
Other β-Lactam Antibiotics
- Carbapenems:
- Imipenem (given IV)
- Meropenem and ertapenem (broader spectrum and less renal toxicity)
- Monobactams:
- Aztreonam (given IV and IM)
- Narrow spectrum, effective against aerobic Gram-negative organisms
- No cross-allergy with penicillins
Vancomycin
- Mechanism of action: inhibits synthesis of bacterial cell wall phospholipids
- Spectrum and uses:
- Effective against Gram-positive organisms (e.g., MRSA and enterococcal infections)
- Used in severe infections in patients allergic to β-lactams
- Used in antibiotic-associated colitis due to C. difficile (e.g., clindamycin)
- Pharmacokinetics:
- Given by IV infusion
- May require dose adjustment in pregnancy and lactation
Choosing an Antimicrobial Agent
- Factors to consider:
- Organism's identity
- Site of infection
- Patient factors
- Safety of the agent
- Cost of therapy
- Classification of antibacterial drugs:
- Bactericidal (kill the organism)
- Bacteriostatic (stop the growth of the organism)
- According to the antibacterial spectrum:
- Narrow spectrum: effective against single or limited group of microorganisms
- Extended spectrum: effective against Gram-positive and a significant number of Gram-negative organisms
This quiz covers the combination of antibiotics with beta-lactamase inhibitors to protect against inactivation by beta-lactamase-producing organisms. It includes examples of antibiotic combinations and their pharmacokinetics.
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