The Calvert formula doses carboplatin to a target exposure (AUC) rather than by body surface area, which is why it needs an accurate glomerular filtration rate. This page explains the formula, how GFR is estimated, why the 125 mL/min cap matters, and the hard limits on using any calculator for chemotherapy dosing.

How the Calvert formula works

Carboplatin's toxicity and efficacy track its exposure over time, measured as the area under the concentration-time curve (AUC). The Calvert formula sets the dose to hit a target AUC: total dose (mg) = target AUC × (GFR + 25), where GFR is in mL/min and the fixed 25 mL/min represents carboplatin's non-renal clearance. Because the dose scales directly with GFR, an inaccurate GFR translates one-for-one into an inaccurate — potentially dangerous — dose.

The target AUC is chosen by the treating oncology team for the specific regimen; common values are roughly AUC 5–7 for single-agent carboplatin, AUC 4–6 in combination, and about AUC 2 for weekly or radiosensitizing schedules.

Estimating GFR and the FDA 125 mL/min cap

When a measured GFR (for example from a nuclear-medicine clearance study) is not available, this tool estimates it with the Cockcroft-Gault equation from age, sex, weight, and serum creatinine. Cockcroft-Gault was developed before creatinine assays were standardized. With today's IDMS-traceable assays, reported creatinine is lower, which pushes the estimated GFR higher and would inflate the carboplatin dose.

To prevent this, the FDA recommended in 2010 that the GFR used in the Calvert formula be capped at 125 mL/min for patients with normal renal function, making the maximum dose AUC × (125 + 25) = AUC × 150. This calculator applies the cap by default; you can turn it off, but doing so is flagged as a potential overdose risk.

Limits and safe use

This calculator is an educational reference only. Real carboplatin orders depend on factors it does not model: the appropriate AUC target, actual versus ideal body weight in obesity, unstable or rapidly changing renal function, prior toxicity, drug interactions, and institutional dose-capping policies. Estimated GFR from a single creatinine can be unreliable, and measured GFR is preferred when precision matters.

Chemotherapy dosing is maximally high-risk. Every carboplatin dose must be calculated and independently double-checked by an oncology pharmacist or oncologist against the institutional protocol and current prescribing information before it is administered.