24 Questions
What is the primary indication for the use of Nalidixic acid?
Urinary tract infections
Why are quinolones not recommended for use during pregnancy?
Risk of fetal toxicity
What is the primary mechanism of action of Sulphonamide and Trimethoprim combination?
Inhibiting folic acid synthesis
Which of the following is NOT a 3rd generation fluoroquinolone?
Norfloxacin
What is the primary indication for the use of Rifampicin?
Tuberculosis treatment
Why are some antibiotics restricted in pregnancy and specific ages?
Due to toxicity concerns
What is the primary mechanism of action of Moxifloxacin?
Inhibiting DNA synthesis
Which of the following is an anaerobic antibiotic?
Clinafloxacin
What is the primary mechanism by which sulfa drugs are eliminated?
Glomerular filtration
What is the cause of crystalluria in patients taking sulfa drugs?
Insolubility of sulfa drugs in acidic urine
What is the risk of kernicterus in newborns associated with?
Displacement of bilirubin from binding sites on serum albumin
What is the mechanism of enzyme induction caused by rifampicin?
Induction of cytochrome P450
What is the common adverse effect of metronidazole?
Unpleasant metallic taste
What is the primary use of cotrimoxazole?
Urinary and respiratory tract infections
What is the consequence of sulfonamide use in infants < 2 months of age?
Kernicterus
What is the adverse effect of trimethoprim that is related to folic acid?
Megaloblastic anemia
What is the primary mechanism by which fluoroquinolones are absorbed?
Decreased absorption with antacids
Which of the following organisms is sensitive to levofloxacin?
Klebsiella
What is the primary route of elimination for most fluoroquinolones?
Renal route
What is a contraindication for the use of Moxifloxacin?
All of the above
What is the primary adverse effect of fluoroquinolones on the central nervous system?
Headache
What is the primary indication for the use of sulfonamides in inflammatory bowel disease?
Anti-inflammatory
What is a characteristic of fluoroquinolones that makes them effective against intracellular organisms?
Accumulation in macrophages
What is the primary reason why fluoroquinolones are avoided in children under 18 years of age?
Risk of arthropathy and ruptured tendons
Study Notes
Pharmacokinetics of Sulfonamides
- Well absorbed
- Penetrate well into cerebrospinal fluid and placental barrier, entering fetal tissues
- Metabolized in the liver through acetylation (metabolites are insoluble in acidic urine → Crystalluria)
- Eliminated by glomerular filtration
Adverse Effects of Sulfonamides
- Crystalluria and nephrotoxicity (↓ by adequate hydration and alkalinization of urine)
- Hypersensitivity: rashes, angioedema, and Stevens-Johnson syndrome
- Hemopoietic disturbances: Hemolytic anemia in patients with G6PD deficiency, leucopenia, and thrombocytopenia
- Kernicterus in newborns: displace bilirubin from binding sites on serum albumin
Contraindications of Sulfonamides
- Infants < 2 months of age
- Pregnant women
Trimethoprim
- Adverse effects: Folic acid deficiency, megaloblastic anemia, and leukopenia
Cotrimoxazole
- Combination of sulfamethoxazole and Trimethoprim (ratio 5:1)
- Bactericidal and broad-spectrum
- Antibacterial spectrum: Urinary and Respiratory Tract Infections, Systemic salmonella infections (Typhoid fever)
- Adverse effects: Sulfa and TMP
- Drug interactions: Sulfonamide ↑ free level of warfarin and Methotrexate (Transistent potentiation)
Rifampicin (Rifampin)
- Antimicrobial spectrum and uses: T.B. prophylaxis against meningitis
- Adverse effects: Red discoloration of urine, tears, and contact lenses, enzyme induction (serious drug interactions), flu-like syndrome, and hepatotoxicity
Metronidazole (Flagyl)
- Uses: Anaerobic protozoal infections (Amebiasis, Giardiasis, Trichomoniasis), Anaerobic bacterial infections (Pseudomembranous colitis due to clostridium difficile), and dental infections
- Adverse effects:
- GIT: unpleasant metallic taste, stomatitis, nausea, and vomiting
- BMS161:
Quinolones
- 1st generation: Nalidixic acid (used as urinary antiseptic)
- 2nd generation: Norfloxacin (UTI)
- 3rd generation: Levofloxacin (Respiratory FQ, Gram +ve Cocci, Staph)
- 4th generation: Moxifloxacin (Anaerobic, Clinafloxacin)
- Pharmacokinetics:
- Absorption: ↓ Absorption with antacids (Al, Mg) or dietary supplements (Zn & Ca)
- Distribution: High levels in bone, urine, kidney, prostatic tissue, and lung; penetrate into cerebrospinal fluid (except for ofloxacin); accumulate in macrophages
- Elimination: Excreted by renal route (except Moxifloxacin, which is excreted by liver)
- Adverse reactions:
- GIT: nausea, vomiting, and diarrhea
- CNS: Headache, dizziness (use cautiously in epilepsy)
- Phototoxicity, Connective tissue problems: Arthropathy and ruptured tendon in adults
This quiz covers the absorption, distribution, metabolism, and excretion of sulfa drugs, as well as their adverse effects, including crystalluria and hypersensitivity reactions.
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