Pharmacokinetics of Sulfa Drugs

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Questions and Answers

What is the primary indication for the use of Nalidixic acid?

Bone infections

Skin infections

Pneumonia

Urinary tract infections (correct)

Why are quinolones not recommended for use during pregnancy?

Unknown reasons

Increased risk of allergy

Risk of fetal toxicity (correct)

Inefficient in placental barrier

What is the primary mechanism of action of Sulphonamide and Trimethoprim combination?

Inhibiting cell wall synthesis

Inhibiting DNA synthesis

Inhibiting protein synthesis

Inhibiting folic acid synthesis (correct)

Which of the following is NOT a 3rd generation fluoroquinolone?

Norfloxacin Signup and view all the answers

What is the primary indication for the use of Rifampicin?

Tuberculosis treatment Signup and view all the answers

Why are some antibiotics restricted in pregnancy and specific ages?

Due to toxicity concerns Signup and view all the answers

What is the primary mechanism of action of Moxifloxacin?

Inhibiting DNA synthesis Signup and view all the answers

Which of the following is an anaerobic antibiotic?

Clinafloxacin Signup and view all the answers

What is the primary mechanism by which sulfa drugs are eliminated?

Glomerular filtration Signup and view all the answers

What is the cause of crystalluria in patients taking sulfa drugs?

Insolubility of sulfa drugs in acidic urine Signup and view all the answers

What is the risk of kernicterus in newborns associated with?

Displacement of bilirubin from binding sites on serum albumin Signup and view all the answers

What is the mechanism of enzyme induction caused by rifampicin?

Induction of cytochrome P450 Signup and view all the answers

What is the common adverse effect of metronidazole?

Unpleasant metallic taste Signup and view all the answers

What is the primary use of cotrimoxazole?

Urinary and respiratory tract infections Signup and view all the answers

What is the consequence of sulfonamide use in infants < 2 months of age?

Kernicterus Signup and view all the answers

What is the adverse effect of trimethoprim that is related to folic acid?

Megaloblastic anemia Signup and view all the answers

What is the primary mechanism by which fluoroquinolones are absorbed?

Decreased absorption with antacids Signup and view all the answers

Which of the following organisms is sensitive to levofloxacin?

Klebsiella Signup and view all the answers

What is the primary route of elimination for most fluoroquinolones?

Renal route Signup and view all the answers

What is a contraindication for the use of Moxifloxacin?

All of the above Signup and view all the answers

What is the primary adverse effect of fluoroquinolones on the central nervous system?

Headache Signup and view all the answers

What is the primary indication for the use of sulfonamides in inflammatory bowel disease?

Anti-inflammatory Signup and view all the answers

What is a characteristic of fluoroquinolones that makes them effective against intracellular organisms?

Accumulation in macrophages Signup and view all the answers

What is the primary reason why fluoroquinolones are avoided in children under 18 years of age?

Risk of arthropathy and ruptured tendons Signup and view all the answers

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

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Description

This quiz covers the absorption, distribution, metabolism, and excretion of sulfa drugs, as well as their adverse effects, including crystalluria and hypersensitivity reactions.