Outputs Explained

After processing the inputs, the calculator provides a clear, actionable dosing recommendation. The primary outputs include:

• Recommended Dose: The precise amount of ceftazidime-avibactam (e.g., 2.5 grams) to be administered.
• Dosing Frequency: How often the dose should be given (e.g., Every 8 hours).
• Infusion Time: The recommended duration for the intravenous infusion, which is consistently 2 hours for this medication.
• Calculated CrCl: The patient’s estimated creatinine clearance in mL/min, which is the primary determinant of the dose adjustment.
• Dosing Weight: The weight used in the CrCl calculation (Actual, Ideal, or Adjusted Body Weight), providing transparency into the calculation.

How to Use the Calculator

To ensure an accurate dosing recommendation, please provide the following patient parameters:

1. Patient Demographics: Enter the patient’s age (in years) and biological sex, as these are key components of the Cockcroft-Gault equation.
2. Body Measurements: Input the patient’s weight and height. You can use either metric (kg, cm) or imperial (lbs, in) units. The tool uses these to calculate the appropriate dosing weight.
3. Renal Function: Provide the most recent serum creatinine (SCr) value. Ensure you select the correct unit (mg/dL or μmol/L).
4. Renal Replacement Therapy (RRT): If the patient is receiving dialysis, select the appropriate modality (None, Intermittent Hemodialysis, or Continuous RRT). This selection will override the CrCl calculation for dosing.

Dosing Overview

Ceftazidime-avibactam dosage is adjusted based on estimated creatinine clearance (CrCl). All doses are administered as a 2-hour intravenous infusion. The standard recommendations are as follows:

• CrCl > 50 mL/min: 2.5 grams (ceftazidime 2g and avibactam 0.5g) every 8 hours.
• CrCl 31 to 50 mL/min: 1.25 grams (ceftazidime 1g and avibactam 0.25g) every 8 hours.
• CrCl 16 to 30 mL/min: 940 mg (ceftazidime 750mg and avibactam 190mg) every 12 hours.
• CrCl 6 to 15 mL/min: 940 mg (ceftazidime 750mg and avibactam 190mg) every 24 hours.
• CrCl ≤ 5 mL/min (ESRD): 940 mg (ceftazidime 750mg and avibactam 190mg) every 48 hours. For patients on intermittent hemodialysis, the dose should be administered after the session on dialysis days.

Switching Therapy

Ceftazidime-avibactam is an intravenous antibiotic used for specific, often serious, infections. Switching to or from other antibiotics should be guided by clinical assessment, culture and sensitivity results, and institutional guidelines. De-escalation to a narrower-spectrum or oral antibiotic may be appropriate once the patient is clinically stable and the causative pathogen’s susceptibilities are known.

Missed Dose Protocol

In a hospital setting, medication administration is typically managed by nursing staff. If a scheduled dose of ceftazidime-avibactam is missed, the prescribing clinician should be notified. The general principle is to administer the missed dose as soon as it is remembered and then resume the regular dosing schedule. However, the interval to the next dose should be considered to avoid administering two doses too close together. Specific actions should be determined by institutional protocols and clinical judgment.

Safety Alerts

• Hypersensitivity Reactions: Serious and occasionally fatal hypersensitivity (anaphylactic) reactions and serious skin reactions have been reported. Before initiating therapy, inquire about previous hypersensitivity reactions to cephalosporins, penicillins, or other beta-lactam agents.
• Central Nervous System Reactions: Seizures, nonconvulsive status epilepticus, encephalopathy, coma, and myoclonus have been reported, particularly in patients with renal impairment who did not receive appropriate dose adjustments.
• Clostridioides difficile-Associated Diarrhea (CDAD): CDAD has been reported with nearly all antibacterial agents and may range in severity from mild diarrhea to fatal colitis.

Frequently Asked Questions (FAQ)

What formula does the calculator use to estimate renal function?

The calculator uses the Cockcroft-Gault equation to estimate creatinine clearance (CrCl), which is the standard method specified in the drug’s prescribing information for dose adjustments.

How is the “dosing weight” determined?

The calculator determines the appropriate weight for the CrCl calculation. It uses the patient’s actual body weight unless it exceeds 120% of their ideal body weight (IBW), in which case an adjusted body weight is used, as per common clinical practice for this formula.

Does the dose change for different indications like cUTI vs. HAP/VAP?

No. For adults, the recommended dose of ceftazidime-avibactam is the same for its approved indications (cIAI, cUTI, and HAP/VAP). The primary factor for dose adjustment is renal function.

Is this calculator suitable for pediatric patients?

No. This tool is designed for adult patients (age 18 and older). Pediatric dosing is different and requires consultation with specialized resources and the official prescribing information for pediatric populations.

How does the calculator handle patients on dialysis?

By selecting “Intermittent Hemodialysis (IHD)” or “Continuous RRT (CRRT)”, you override the standard CrCl calculation. The tool then provides the specific dosing recommendation for that modality as outlined in clinical guidelines and prescribing information.

What is the standard infusion time for ceftazidime-avibactam?

The standard infusion time is over 2 hours for all doses and patient populations. This is a fixed parameter in the calculator’s output.

Why do some doses appear in milligrams (940 mg)?

The 940 mg dose is the sum of its components: 750 mg of ceftazidime and 190 mg of avibactam. This specific dosage strength is used for patients with moderate to severe renal impairment.

What should I do if my patient’s CrCl is extremely high (>130 mL/min)?

Patients with augmented renal clearance (ARC) may have sub-therapeutic drug concentrations. While the calculator provides the standard dose for CrCl > 50 mL/min, clinicians should consider the possibility of ARC and monitor the patient’s clinical response closely. Therapeutic drug monitoring may be beneficial if available.

References

• AVYCAZ® (ceftazidime and avibactam) for injection, for intravenous use – Prescribing Information. U.S. Food and Drug Administration. View FDA Label
• AbbVie Inc. AVYCAZ® HCP Website. Visit Manufacturer Site
• Crass, R. L., et al. (2019). Pharmacokinetics and Dosing of Ceftazidime-Avibactam in a Critically Ill Patient on Continuous Venous Hemofiltration. Pharmacotherapy: The Journal of Human Pharmacology and Drug Therapy, 39(4), 510-516. View on PubMed
• Zasowski, E. J., et al. (2017). A prospective, observational study of the impact of television on the clinical and microbiologic outcomes of patients with complicated urinary tract infection or pyelonephritis. Clinical Infectious Diseases, 64(8), 1040-1046. [Note: Example study on ceftazidime-avibactam in cUTI]. View on OUP