Aztreonam

Common Uses

Aztreonam is primarily used to treat severe infections caused by certain types of bacteria. Healthcare providers may prescribe the injectable form for the following conditions:

• Urinary tract infections: Including both simple and complicated infections of the bladder or kidneys.
• Respiratory infections: Such as pneumonia and other lower respiratory tract issues.
• Skin and soft tissue infections: Including infected wounds or ulcers.
• Abdominal infections: Such as peritonitis or other infections within the stomach area.
• Gynecologic infections: Including pelvic inflammatory disease and endometritis.
• Blood and brain infections: Such as septicemia (blood poisoning) and meningitis.

Cystic Fibrosis

An inhaled version of aztreonam is used specifically for people with cystic fibrosis. It helps improve lung function and reduce respiratory symptoms in patients who have a chronic infection caused by the bacteria Pseudomonas aeruginosa.

Special Considerations

Aztreonam is often used in hospital settings for serious or complex infections. It is frequently chosen as an alternative antibiotic for patients who have a known allergy to penicillin or cephalosporins, as it is generally considered safe for those individuals. In some cases, it is used in combination with other drugs to treat resistant bacteria, hospital-acquired pneumonia, or complicated intra-abdominal infections.

How Aztreonam Works

Aztreonam belongs to a class of antibiotics known as monobactams. It is designed to target and eliminate specific types of bacteria, known as aerobic Gram-negative bacteria, which are responsible for various types of infections.

Disrupting the Cell Wall

Bacteria require a sturdy outer layer called a cell wall to survive, maintain their shape, and protect themselves from their environment. Aztreonam works by binding to specific proteins within the bacterial cell. This action prevents the bacteria from properly synthesizing or repairing their cell walls. As the cell wall weakens, the bacteria can no longer contain their internal pressure, causing them to burst and die.

Targeted Action

Aztreonam is unique because of its narrow spectrum of activity. It primarily focuses on:

• Aerobic bacteria: Bacteria that need oxygen to grow and multiply.
• Gram-negative bacteria: A group of bacteria characterized by a specific cell wall structure that can be difficult for some other antibiotics to penetrate.

Because it targets these specific organisms, it does not typically affect Gram-positive bacteria or anaerobic bacteria (those that live without oxygen). This targeted approach helps treat specific infections in the lungs, urinary tract, blood, and other areas of the body.

Common Side Effects

The following side effects are more common and may occur during treatment:

• Nausea or vomiting
• Diarrhea
• Stomach pain
• Headache
• Dizziness
• Fever
• Skin rash
• Pain, redness, or swelling at the site of injection
• Cough, sore throat, or nasal congestion when using the inhaled form

Serious Side Effects

Seek medical attention immediately if you experience any of the following serious symptoms:

• Signs of a severe allergic reaction, including hives, itching, or swelling of the face, throat, or limbs
• Difficulty breathing, wheezing, or shortness of breath
• Severe watery or bloody diarrhea and stomach cramps, which may occur during treatment or several months after stopping the medication
• Unusual bruising or bleeding
• Yellowing of the skin or the whites of the eyes
• Chest pain or tightness

Hypersensitivity Reactions

Serious and occasionally fatal allergic reactions, including anaphylaxis, have been reported with the use of aztreonam. While this medication is often tolerated by individuals with penicillin or cephalosporin allergies, caution is necessary for those with a history of severe immediate reactions to beta-lactam antibiotics. There is a specific risk of cross-reactivity in patients allergic to ceftazidime due to structural similarities between the two drugs.

Clostridioides difficile-Associated Diarrhea

Treatment with aztreonam can alter the normal flora of the colon, leading to the overgrowth of Clostridioides difficile. This can result in diarrhea ranging in severity from mild to life-threatening colitis. This condition may occur during treatment or several months after the medication is discontinued.

Inhalation Precautions

The inhaled form of aztreonam may cause bronchospasm, which is a sudden narrowing of the airways that makes breathing difficult. This risk is higher in patients with a history of hyperreactive airways. Medical providers often recommend using a bronchodilator before each dose of the inhaled medication to reduce this risk.

Organ Impairment and Monitoring

Patients with decreased kidney or liver function may require dosage adjustments. Healthcare providers typically monitor renal and hepatic function during prolonged therapy, especially in patients with pre-existing impairment or in elderly patients who may have age-related declines in organ function.

Other Considerations

• Superinfection: As with other antibiotics, prolonged use may lead to the overgrowth of non-susceptible organisms, including fungi.
• Antibiotic Resistance: Using aztreonam in the absence of a proven or strongly suspected bacterial infection is unlikely to provide benefit and increases the risk of developing drug-resistant bacteria.
• Blood Disorders: Rare instances of blood cell changes, such as a decrease in certain white blood cells or platelets, have been observed during treatment.

Pregnancy

Studies in animals have not shown that aztreonam causes birth defects or other developmental problems. However, there are no adequate and well-controlled studies in pregnant women to confirm its safety. Aztreonam is known to cross the placenta and enter fetal circulation. Because of the limited human data, healthcare providers typically prescribe aztreonam during pregnancy only if the potential benefits outweigh the potential risks to the fetus.

Breastfeeding

Aztreonam is excreted in human breast milk in very low concentrations, often less than 1% of the dose the mother receives. While it is generally considered safe to use while nursing, healthcare providers may discuss the following considerations:

• The decision to continue or temporarily stop breastfeeding while taking the medication.
• The possibility of using infant formula during the course of treatment.
• Monitoring the nursing infant for any changes, such as diarrhea or diaper rash, which could indicate an effect on the baby's digestive system.

Always consult with a healthcare professional to determine the most appropriate course of action for your specific situation.

Injectable Forms

Aztreonam is commonly supplied in the following injectable formats:

• Powder for Injection: A sterile powder that must be mixed with a compatible liquid before being administered into a vein (intravenous) or a muscle (intramuscular).
• Premixed Solution: A ready-to-use liquid solution for intravenous infusion, often provided in frozen or plastic containers.

Inhalation Form

Aztreonam is available as a solution for inhalation. This form is specifically designed to be used with a nebulizer system to deliver the medication directly to the lungs.

Combination Products

Aztreonam may also be found in combination with other medications, such as avibactam, provided as a powder for intravenous infusion.

FDA Approval and Indications

Aztreonam was first approved by the U.S. Food and Drug Administration (FDA) in 1986. It is a monobactam antibiotic primarily used to treat infections caused by susceptible gram-negative bacteria. The injectable form is FDA-approved for the following conditions:

• Urinary tract infections
• Lower respiratory tract infections
• Septicemia (bloodstream infections)
• Skin and skin structure infections
• Intra-abdominal infections
• Gynecologic infections

The inhaled formulation of aztreonam is specifically approved to improve respiratory symptoms in patients with cystic fibrosis who have Pseudomonas aeruginosa lung infections. It is intended for use in patients aged 7 years and older.

Recent Regulatory Status

In 2024, the FDA approved a combination of aztreonam and avibactam for the treatment of complicated intra-abdominal infections, hospital-acquired bacterial pneumonia, and ventilator-associated bacterial pneumonia in adults. This combination is designed to treat infections where limited or no other treatment options are available.

Safety and Oversight

Aztreonam does not currently have any boxed warnings or Risk Evaluation and Mitigation Strategies (REMS) requirements. The medication remains under standard FDA monitoring for safety and efficacy across its various approved uses.