Standard Creatinine Clearance Formula Used in Tigecycline Dosing
Tigecycline dosing adjustments, as in tools from Pfizer's labeling or clinical calculators (e.g., MDCalc, GlobalRPh), rely on the Cockcroft-Gault formula to estimate creatinine clearance (CrCl). This determines if severe impairment (CrCl ≤30 mL/min) requires a 50% loading dose reduction and 75% maintenance dose reduction.[1]
Cockcroft-Gault equation:
CrCl (mL/min) = [(140 - age in years) × weight in kg × (0.85 if female)] / (72 × serum creatinine in mg/dL)
Key Inputs for Tigecycline Tools
- Age: Patient's age in years (older age lowers CrCl).
- Weight: Actual body weight in kg (ideal body weight sometimes used if obese, per tool variations).
- Serum creatinine: Most recent level in mg/dL (or μmol/L, converted by dividing by 88.4).
- Sex: Multiplier of 0.85 for females accounts for lower muscle mass.
Tools auto-convert units and flag adjustments: no change for CrCl >80 mL/min; reductions only for ≤30 mL/min (end-stage renal disease often needs dialysis review).[1][2]
Why Cockcroft-Gault Over CKD-EPI for Tigecycline?
Cockcroft-Gault remains the regulatory standard in tigecycline's FDA/EMA labels, despite CKD-EPI's accuracy in modern studies. Dosing trials (e.g., phase 3 data) validated it against measured clearance. Tools stick to this to match package insert recommendations.[1][3]
Adjustments and Limitations in Practice
| CrCl (mL/min) | Loading Dose | Maintenance Dose |
|---------------|--------------|------------------|
| >80 | 100 mg | 50 mg q12h |
| ≤30 | 50 mg | 25 mg q12h |
Limitations: Overestimates in obesity (use adjusted weight); underestimates in extremes of age/muscle mass. Hepatic impairment drives separate adjustments, not renal.[1] Always verify with measured CrCl if unstable.
Online Tools Using This Calculation
- MDCalc Tigecycline Doser: Inputs age, weight, sex, Cr, auto-applies Cockcroft-Gault.[2]
- GlobalRPh: Includes hepatic/renal combo tool with same formula.[4]
- Pfizer Resources: Label-linked calculators reference it directly.
[1]: Tigecycline Prescribing Information (Pfizer)
[2]: MDCalc Tigecycline Dosing
[3]: FDA Label Approval Summary
[4]: GlobalRPh Tigecycline Calculator