Aztreonam is Not Available for Oral Administration
Aztreonam is only available for parenteral (intravenous or intramuscular) administration and as an inhaled formulation for specific indications, but not as an oral medication due to its poor oral bioavailability of approximately 1%. 1
Available Administration Routes for Aztreonam
Aztreonam belongs to the monobactam class of antibiotics and has specific administration routes:
- Parenteral administration:
- Intravenous (IV)
- Intramuscular (IM)
- Inhaled formulation: Used specifically for patients with cystic fibrosis and Pseudomonas aeruginosa infections 2
The poor oral bioavailability (approximately 1%) makes oral administration ineffective for treating systemic infections, which is why no oral formulation has been developed 1, 3.
Pharmacokinetic Properties
The pharmacokinetic profile of aztreonam explains why it must be administered parenterally:
- Half-life: 1.5-2.1 hours in patients with normal renal function 3
- Dosing interval: Typically every 8 hours for moderate to severe infections 3
- Primary elimination: Via the kidneys, with dosage adjustments required in renal impairment 3
Clinical Applications
Aztreonam is primarily used for:
- Gram-negative aerobic bacterial infections, particularly Enterobacteriaceae and Pseudomonas aeruginosa 1
- Specific indications include:
- Urinary tract infections
- Lower respiratory tract infections
- Intra-abdominal infections
- Gynecological infections
- Septicemia
- Skin and soft tissue infections 4
Important Clinical Considerations
- Spectrum of activity: Aztreonam has a narrow spectrum focused on aerobic gram-negative bacteria and is inactive against gram-positive and anaerobic bacteria 1
- Combination therapy: When treating mixed infections or infections of unknown etiology, aztreonam should be combined with agents active against gram-positive and/or anaerobic bacteria 4
- Inhaled formulation: The inhaled form is specifically indicated for patients with cystic fibrosis who have Pseudomonas aeruginosa infections 2
Pitfalls to Avoid
- Do not confuse with oral antibiotics: Unlike many other antibiotics that have both oral and parenteral formulations, aztreonam is strictly for parenteral or inhaled use
- Do not use as monotherapy for mixed infections: Due to its narrow spectrum, aztreonam alone is insufficient for polymicrobial infections involving gram-positive or anaerobic organisms 4
- Dosage adjustment in renal impairment: Failure to adjust dosage in patients with kidney dysfunction can lead to drug accumulation 3
In summary, aztreonam requires parenteral or inhaled administration for effective treatment of susceptible infections, and no oral formulation exists due to its extremely poor oral bioavailability.