Carboplatin AUC Dose Calculator (Calvert Formula)

Calculate Carboplatin AUC Dose

Carboplatin AUC Dose (Calvert Formula)

Formula

\[ \text{GFR} = \frac{(140 - \text{age}) \times \text{weight (kg)}}{72 \times \text{serum creatinine (mg/dL)}} \times 0.85 \;\text{(if female)} \] \[ \text{Carboplatin Dose (mg)} = \text{Target AUC} \times (\text{GFR} + 25) \]

Where:

\(\text{GFR}\) — glomerular filtration rate, estimated with the Cockcroft-Gault equation (mL/min)
\(\text{age}\) — patient age in years
\(\text{weight}\) — body weight in kilograms
\(\text{serum creatinine}\) — serum creatinine in mg/dL
\(0.85\) — correction factor applied for female patients
\(\text{Target AUC}\) — desired area under the concentration-time curve (mg/mL·min)
\(25\) — non-renal clearance of carboplatin (mL/min)

The first equation estimates kidney function using the Cockcroft-Gault method; the second, the Calvert formula, converts that estimate plus the target drug exposure (AUC) into a carboplatin dose in milligrams.

Carboplatin AUC Dose – Calculation Example

Example: a 25-year-old man weighing 70 kg with a serum creatinine of 1.0 mg/dL is prescribed carboplatin with a target AUC of 5.

\[ \text{GFR} = \frac{(140 - 25) \times 70}{72 \times 1.0} = \frac{8050}{72} \approx 111.81 \;\text{mL/min} \]

\[ \text{Dose} = 5 \times (111.81 + 25) = 5 \times 136.81 \approx 684.03 \;\text{mg} \]

Result: GFR ≈ 111.81 mL/min and a carboplatin dose of ≈ 684.03 mg. These match the calculator's default values, so you can reproduce them directly.

How to use the calculator

Select the patient's Gender (Male or Female). A factor of 0.85 is applied to the GFR estimate for female patients.
Enter the patient's Age in years.
Enter the Weight and choose the unit — kg or lb. Pounds are converted to kilograms automatically.
Enter the Serum Creatinine value in mg/dL from the patient's recent lab results.
Enter the prescribed Target AUC in mg/mL·min — commonly 4 to 7, depending on the treatment protocol.
Read the results: the estimated GFR in mL/min and the Carboplatin Dose in mg.

What the Calvert formula means

Carboplatin is a platinum-based chemotherapy drug used to treat ovarian, lung, head and neck, and several other cancers. Unlike most cytotoxic drugs, it is dosed to a target area under the curve (AUC) rather than to body surface area. The AUC describes total drug exposure over time: a higher AUC means more drug effect — and more toxicity.

The Calvert formula, introduced in 1989, links the desired exposure to the dose that will produce it: dose = target AUC × (GFR + 25). The term GFR represents renal clearance, since carboplatin is eliminated almost entirely by the kidneys, while the constant 25 mL/min accounts for the small non-renal clearance. Because clearance varies widely between patients, this approach individualizes the dose far better than a fixed mg/m² regimen.

The calculator estimates GFR with the Cockcroft-Gault equation, which derives creatinine clearance from age, weight, sex and serum creatinine. The female factor of 0.85 reflects women's on-average lower muscle mass and thus lower creatinine production.

Interpreting the result: the output dose is the total amount of carboplatin (in mg) to administer for the chosen AUC, typically diluted and infused over 30–60 minutes. Typical targets are AUC 4–6 for combination regimens and AUC 5–7 for single-agent therapy, but the correct value always comes from the treatment protocol.

Assumptions, limitations and practical tips

Renal function estimate only. Cockcroft-Gault is an approximation. In patients with unstable kidney function, extremes of weight, or very low muscle mass, a measured or radionuclide GFR is preferred for Calvert dosing — this is a known source of dosing error.
Creatinine units matter. The calculator expects serum creatinine in mg/dL. If your lab reports µmol/L, divide by 88.4 before entering the value.
Use actual body weight cautiously. Cockcroft-Gault was developed with actual body weight; in markedly obese or very underweight patients, many protocols use adjusted or ideal body weight instead. Check your institutional guideline.
Overestimation risk. Overestimating GFR leads to overdosing and myelosuppression, the dose-limiting toxicity of carboplatin. When in doubt, prescribers often cap the GFR estimate.
Not for carboplatin desensitization or high-dose protocols. Some settings use different formulas or measured clearance.
Clinical decision tool. This calculator supports verification and education; the final dose must be confirmed by an oncologist or clinical pharmacist against the specific protocol.

For related calculations, see the Half-Life Time calculator to estimate drug elimination, the Dosage Infusion calculator for infusion rate calculations, or the Dialysis Dose (Kt/V) calculator for assessing dialysis adequacy in patients with severe renal impairment.

Frequently Asked Questions

Why does the Calvert formula add 25 to the GFR?

The 25 mL/min constant represents carboplatin's non-renal clearance — the small fraction of the drug cleared by routes other than the kidneys. Total clearance equals renal clearance (approximated by GFR) plus this fixed 25 mL/min, so the dose formula becomes \( \text{AUC} \times (\text{GFR} + 25) \). Even patients with severely reduced kidney function still receive some drug clearance through this non-renal component.

What is a normal GFR value for carboplatin dosing?

Healthy adults typically have a GFR of 90–120 mL/min, which Cockcroft-Gault approximates reasonably well in average-built patients. Values below 60 mL/min indicate reduced kidney function and yield lower carboplatin doses. Note that Cockcroft-Gault can overestimate true GFR in elderly or low-muscle-mass patients, which is why many protocols cap the GFR used in the Calvert formula at around 125 mL/min.

How do I convert serum creatinine from µmol/L to mg/dL?

Divide the µmol/L value by 88.4 to get mg/dL. For example, a creatinine of 80 µmol/L equals about 0.90 mg/dL. Entering µmol/L values directly would massively underestimate GFR and produce a dangerously low dose, so double-check the units on the lab report before calculating.

Which AUC value should I use — 4, 5, 6 or 7?

There is no universal answer; the target AUC comes from the specific treatment protocol. Commonly, AUC 4–6 is used in combination chemotherapy (e.g., with paclitaxel), while AUC 5–7 is typical for single-agent carboplatin. Higher AUC values increase both efficacy risk-balance and toxicity, especially suppression of blood counts. The prescribing oncologist determines the correct target for each patient and cycle.

Should I use actual, ideal or adjusted body weight in the formula?

Cockcroft-Gault was originally developed with actual body weight, and that is what this calculator uses. However, in markedly obese patients actual weight can overestimate GFR, and in very underweight patients it can underestimate it. Many institutions substitute adjusted body weight (ABW) or ideal body weight (IBW) for obese patients — always check your local guideline before dosing.

Can this calculator be used for children or patients on dialysis?

No. The Cockcroft-Gault equation was validated in adults and performs poorly in children, where other GFR-estimating formulas are used. Patients on dialysis or with severely impaired renal function require special dosing approaches, sometimes with measured clearance or protocol-specific caps on the GFR term. These situations need individualized decisions by an oncology specialist.

Is the calculated dose given every treatment cycle?

Yes — the result is the total dose in mg for one carboplatin administration, usually infused over 30–60 minutes, and it is recalculated each cycle because renal function can change during treatment. Always confirm the final dose, dilution and infusion time with the treating oncologist or clinical pharmacist; this tool is for verification and education, not for independent clinical decisions.

Carboplatin AUC Dose Calculator