Pharmacokinetics of Aztreonam

Pharmacokinetics of Aztreonam

• Aztreonam is not absorbed orally and is administered as an IM injection
• Half-life in adults with normal renal function: 1.4-2.2 hours
• 60-70% of the drug is eliminated in the urine within 8 hours

Adverse Reactions of Aztreonam

• Common: gastric distress, diarrhea, nausea/vomiting, hypersensitivity, and thrombophlebitis at the injection site
• Rare: anaphylaxis, hepatitis, jaundice, thrombocytopenia, and prolonged bleeding time
• Caution: low risk of allergic reaction in those allergic to penicillins or cephalosporins

Aminoglycosides

• Includes: amikacin, gentamycin, tobramycin, and neomycin (oral)
• Mechanism of Action: bind irreversibly to the 30S ribosomal subunit, inhibiting protein synthesis and leading to cell death
• Indications: serious or life-threatening Gram-negative infections, especially those caused by Pseudomonas, E. coli, Proteus, Klebsiella, Serratia, and enterococci
• Pharmacokinetics:
  • Strongly polar molecules, do not distribute to the CNS
  • Tissue concentrations are low
  • Eliminated by the kidneys in people with normal renal function
  • Plasma half-life: 2-3 hours
  • Monitoring plasma concentrations is essential to ensure therapeutic concentrations without adverse reactions

Chloramphenicol

• Bacteriostatic agent effective against Gram-negative and Gram-positive organisms and anaerobes
• Indications: Haemophilus influenzae, Streptococcus pneumoniae, and Neisseria meningitidis
• Contraindications: pre-existing bone marrow suppression and/or blood dyscrasias
• Mechanism of Action: inhibits protein synthesis by binding to the 50S sub-unit of the bacterial ribosome

Lincosamides

• Includes: lincomycin and clindamycin
• Mechanism of Action: inhibits protein synthesis by binding to the 50S ribosomal sub-unit and preventing peptide bond formation
• Indications: serious streptococcal and staphylococcal infections
• Pharmacokinetics:
  • Half-life in adults: 2-3 hours
  • Reaches peak blood concentrations within 0.75-1 hour of oral administration in adults, 1 hour in children, and 3 hours after IM injection
  • May cause thrombocytopenia, leucopenia, eosinophilia, and neutropenia; full blood count should be monitored during therapy

Tetracyclines

• Includes: doxycycline, minocycline, and tetracycline
• Mechanism of Action: inhibits protein synthesis by reversibly blocking the 30S sub-unit of the ribosome and preventing access of tRNA to the mRNA-ribosome complex
• Indications: acne vulgaris, actinomycosis, anthrax, bacterial urinary tract infections (UTIs), bronchitis, and numerous systemic bacterial infections
• Adverse Reactions:
  • Common: dizziness (minocycline), esophagitis (doxycycline), ataxia, gastrointestinal distress, photosensitivity, discoloration of infants' or children's teeth
  • Rare: hepatotoxicity, pancreatitis, and benign intracranial hypertension

Inhibitors of DNA Synthesis

Fluoroquinolones

• Includes: ciprofloxacin, moxifloxacin, norfloxacin, and ofloxacin
• Mechanism of Action: interferes with bacterial topoisomerase II (DNA gyrase) and topoisomerase IV, essential for DNA duplication, transcription, and repair
• Indications: bone and joint infections, Legionella pneumonia, epididymo-orchitis, prostatitis, and complicated UTIs
• Combination with trimethoprim is synergistic, blocking a further step in folic acid synthesis

Methenamine Hippurate

• Used to treat UTIs
• Mechanism of Action: formaldehyde is released, which may be bactericidal or bacteriostatic, causing denaturation of bacterial protein
• Effective in acid medium, ineffective in alkaline urine
• Indications: long-term suppression of infections, due to its low toxicity and low incidence of resistance

Nitrofurantoin

• Bactericidal agent effective against E. coli and S. aureus
• Mechanism of Action: reduced by bacteria to reactive substances that inactivate or alter cell wall synthesis, bacterial ribosomal proteins, and DNA and RNA function
• Indications: acute UTIs and prophylaxis of recurrent UTIs
• Pharmacokinetics:
  • Well absorbed
  • Half-life: 20-60 minutes
  • 65% excreted, mainly as unchanged drug in the urine
• Adverse Effects:
  • Acute allergic pneumonitis
  • Rarely, chronic irreversible interstitial pulmonary fibrosis in older patients following chronic treatment (>6 months)
  • Contraindications: nitrofurantoin hypersensitivity, peripheral neuropathy, lung disease, or moderate-to-severe renal impairment

Learn about the administration, half-life, and adverse reactions of Aztreonam, an antibiotic used to treat bacterial infections.