Compartmental pharmacokinetic modeling
Set up, run, and review this analysis in Lifescio.
Supported analysis
Choose one or two compartments. Positive parameters are fitted by nonlinear least squares. The app plots predictions and residuals and reports local approximate intervals and an identifiability diagnostic.
Supported scope: This is a single pooled curve with independent additive constant-variance errors. Oral absorption, repeated dosing and between-person random effects are not modeled. Local intervals are unreliable when parameters are weakly identified.
Prepare data and configure the analysis
Supply exactly Time and Concentration, with nonnegative values and strictly increasing times. Choose one or two compartments and provide the IV bolus dose in compatible units. The tool fits one concentration curve; there is no subject-ID column or population random-effects model.
The one-compartment fit estimates clearance and central volume; the two-compartment fit also estimates intercompartmental clearance and peripheral volume. Positive parameters are fitted on a transformed scale. At least one concentration must be positive and there must be more observations than parameters.
Input reference (3 fields)
Enter your data and prespecified choices. Ranges include both limits. For table fields, use cell editing, Paste data, or Import CSV / TSV. Review whether the first imported row contains headings and map the source columns before applying the import. Empty numeric cells are not treated as zero. Open file is for an exported Lifescio analysis JSON file, not a spreadsheet.
| Input | Format | Allowed range | Guidance |
|---|---|---|---|
| Concentration–time observations | Table | — | Columns in order: Time; Concentration. |
| Compartments | Selection | — | Choices: one, two. |
| IV bolus dose | Number | 0.000001–1000000 | — |
Run and review
- Give the analysis a descriptive name and review every example value. Record units, data preparation, and planning assumptions in Reproducibility & notes. For simulations, record the seed and replication or sampling settings.
- Choose Run analysis. Resolve input errors before interpreting output. In the connected app, a run uses a saved input revision; local preview runs need the page to stay open.
- Review Diagnostics for method limitations, warnings, and available numerical checks. A completed run means computation finished; it does not establish that the assumptions fit your study.
- Use the Result table selector to inspect each output. Editing inputs does not recalculate existing results: an earlier-input notice means you need to run again to obtain matching results.
Understand the outputs
PK parameters reports estimates and approximate 95% limits. Fit diagnostics gives residual degrees of freedom, residual standard deviation, and the Jacobian condition number. Read any weak-identification warning before interpreting parameter precision.
The PK fit curve spans the observed time range. Residuals compares concentration residuals with fitted concentrations. Intervals are local approximations from nonlinear least squares, not population variability or prediction intervals for a new individual.
Troubleshooting and common mistakes
A convergence or identification failure can reflect insufficient early/late sampling, redundant compartment structure, or incompatible units. Check the administration model and data before retrying a more complex fit.
A high condition number and broad intervals may warrant the simpler model or more informative observations. Oral, infusion, repeated-dose, and mixed-subject data should not be forced into the bolus form. Changing the dose solely to improve the curve alters the scientific input.
After correcting inputs, run again and check that the results belong to the new input snapshot. Increasing simulation draws improves numerical precision only; it does not repair invalid data or an unsuitable model.
Save, compare, and export
In the connected app, Save analysis retains the inputs in your account. Run history lets you inspect earlier runs, each with the input revision it used. In local preview, Save analysis downloads an input file instead; download results before leaving the page.
Use Result + inputs for a JSON archive containing the completed result and its inputs, Download CSV for the selected result table, PDF report for a report, and a chart's SVG button for its figure. Table displays round to three decimals; CSV and JSON exports retain calculation precision. Use those values when assessing a result near a decision boundary.
To reopen an archive, select the matching analysis method and choose Open file. Imported inputs start a new draft; a result archive can also display its retained result. It does not attach itself to an existing account analysis or recompute the result. Save or run the imported draft when you want a new account record.