12 Questions
Which of the following bacteria are resistant to ciprofloxacin?
Bacteroides fragilis, Clostridium difficile, and most anaerobes
Which of the following routes of administration is NOT mentioned for ciprofloxacin?
Intramuscular
Which of the following adverse effects of ciprofloxacin is NOT mentioned in the text?
Muscle weakness and fatigue
Which newer fluoroquinolone has greater activity against streptococci and some activity against anaerobes?
Moxifloxacin
Which of the following is NOT mentioned as a bacterium susceptible to ciprofloxacin?
Acinetobacter baumannii
Which of the following drug interactions with ciprofloxacin is NOT mentioned in the text?
Increased plasma concentration of theophylline
What is the mechanism of action of nalidixic acid?
Inhibition of DNA gyrase enzyme in gram-negative bacteria
Which bacteria is nalidixic acid NOT effective against?
Pseudomonas
What is the main adverse effect associated with fluoroquinolones?
Central nervous system (CNS) effects
What is the mechanism of action of fluoroquinolones?
Inhibition of DNA gyrase enzyme in gram-negative bacteria
Which of the following is a second-generation fluoroquinolone?
Ofloxacin
What is the antibacterial spectrum of ciprofloxacin?
Highly effective against aerobic gram-negative organisms
Study Notes
Quinolones and Fluoroquinolones
- The first quinolone, nalidixic acid, is a urinary antiseptic effective against gram-negative bacteria including E. coli, Proteus, Klebsiella, Enterobacter, Salmonella, and Shigella, but not Pseudomonas.
- Nalidixic acid inhibits DNA gyrase enzyme and interferes with the replication of bacterial DNA.
- It is useful in the treatment of uncomplicated UTI due to gram-negative bacteria and diarrhea due to Shigella or Salmonella.
Mechanism of Action
- Fluoroquinolones (FQs) inhibit bacterial DNA synthesis (bactericidal) by inhibiting DNA gyrase in gram-negative bacteria and topoisomerase IV in gram-positive bacteria.
Antibacterial Spectrum
- Ciprofloxacin is the prototype drug and is highly effective against aerobic gram-negative organisms:
- E. coli
- Coli
- Enterobacter
- Proteus
- Klebsiella
- Salmonella
- Shigella
- H. ducreyi
- H. influenzae
- N. gonorrhoeae
- N. meningitidis
- V. cholerae
- Campylobacter jejuni
- Ciprofloxacin also has activity against S. aureus, Pseudomonas aeruginosa, and M. tuberculosis.
Pharmacokinetics
- Ciprofloxacin is administered by oral, i.v., or topical routes.
- It is well absorbed from the gut, but food delays its absorption.
- It is widely distributed in the body and reaches high concentration in kidney, lung, prostatic tissue, bile, macrophages, etc.
- It is excreted mainly in urine.
Adverse Effects
- Common adverse effects are related to the Gl tract (nausea, vomiting, abdominal discomfort), CNS (headache, dizziness, insomnia, confusion, hallucinations, convulsions), and skin (rashes, urticaria, itching, eosinophilia, photosensitivity).
- Tenosynovitis and tendon rupture can occur, especially in athletes.
- Moxifloxacin can cause prolongation of QT interval.
Contraindications and Precautions
- FQs are contraindicated in pregnancy.
- FQs should be avoided in young children due to the risk of cartilage damage.
Drug Interactions
- Ciprofloxacin increases the plasma concentration of theophylline, warfarin, etc., by inhibiting their metabolism.
- Nonsteroidal anti-inflammatory drugs (NSAIDs) may potentiate CNS side effects of FQs (confusion, irritability, and rarely convulsions).
- Absorption of FQs is reduced by antacids, ferrous salts, and sucralfate.
Test your knowledge about the first quinolone, nalidixic acid, its mechanism of action, and its effectiveness against various gram-negative bacteria including E.coli, Proteus, and Klebsiella.
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