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Questions and Answers
What is the mechanism of action of Vancomycin?
What is the mechanism of action of Vancomycin?
- Inhibition of cell wall synthesis (correct)
- Inhibition of protein synthesis
- Inhibition of folic acid synthesis
- Inhibition of DNA replication
Which of the following antibiotics is effective against Gram +ve and -ve organisms and anaerobes?
Which of the following antibiotics is effective against Gram +ve and -ve organisms and anaerobes?
- Ertapenem
- Penicillin
- Aztreonam
- Imipenem (correct)
What is the main advantage of Meropenem over Imipenem?
What is the main advantage of Meropenem over Imipenem?
- Less renal degradation (correct)
- Narrower spectrum of activity
- Greater risk of convulsions
- Less risk of hypersensitivity
Why is cilastatin often given with Imipenem?
Why is cilastatin often given with Imipenem?
What is the main indication for the use of Vancomycin?
What is the main indication for the use of Vancomycin?
Which of the following antibiotics is considered safe in patients with a history of hypersensitivity to penicillin?
Which of the following antibiotics is considered safe in patients with a history of hypersensitivity to penicillin?
What is the advantage of Ertapenem over Imipenem?
What is the advantage of Ertapenem over Imipenem?
What is the purpose of combining clavulanic acid with amoxicillin in Augmentin?
What is the purpose of combining clavulanic acid with amoxicillin in Augmentin?
What is the main side effect of Imipenem?
What is the main side effect of Imipenem?
Which of the following is NOT a combination of a β-lactam antibiotic with a β-lactamase inhibitor?
Which of the following is NOT a combination of a β-lactam antibiotic with a β-lactamase inhibitor?
What is the mechanism by which probenecid increases the duration of action of penicillin?
What is the mechanism by which probenecid increases the duration of action of penicillin?
What is the primary mechanism of hypersensitivity reactions to penicillin?
What is the primary mechanism of hypersensitivity reactions to penicillin?
Which of the following routes of administration is dependent on the stability of the antibiotic to gastric acidity?
Which of the following routes of administration is dependent on the stability of the antibiotic to gastric acidity?
What is the primary mechanism of action of β-lactam antibiotics?
What is the primary mechanism of action of β-lactam antibiotics?
Which of the following is a characteristic of depot IM preparations of penicillin?
Which of the following is a characteristic of depot IM preparations of penicillin?
What is the primary site of excretion of penicillin?
What is the primary site of excretion of penicillin?
What is the primary goal of antimicrobial therapy after a pathogen is cultured?
What is the primary goal of antimicrobial therapy after a pathogen is cultured?
What is the difference between bactericidal and bacteriostatic antimicrobial drugs?
What is the difference between bactericidal and bacteriostatic antimicrobial drugs?
What is the classification of antimicrobial drugs based on their effect on bacteria?
What is the classification of antimicrobial drugs based on their effect on bacteria?
What is the primary consideration for choosing an antimicrobial agent?
What is the primary consideration for choosing an antimicrobial agent?
What is the significance of the minimum inhibitory concentration (MIC) in antimicrobial therapy?
What is the significance of the minimum inhibitory concentration (MIC) in antimicrobial therapy?
What is the primary mechanism of action of cell wall inhibitors?
What is the primary mechanism of action of cell wall inhibitors?
What is the classification of antimicrobial drugs based on their spectrum of activity?
What is the classification of antimicrobial drugs based on their spectrum of activity?
What is the primary consideration for dosing of β-lactam antibiotics in patients with impaired renal function?
What is the primary consideration for dosing of β-lactam antibiotics in patients with impaired renal function?
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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
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