Bioinformatics & Pharmacology

Loewe Additivity Calculator

Dose-additivity reference modeling & real-time isobolographic analyzer

Principal Developers & Maintainers Dr. Pon Nivedha Rajamanickam, Dr. Jothi Nedunchezhian & Dr. Radha Arulkumar
Academic Department Biotechnology & Bioinformatics
Institution Holy Cross College (Autonomous), Trichy

Batch Excel / CSV Data Processing

Upload multiple combination dose pairs to evaluate CI across full checkerboard plates simultaneously.

Drag and drop your .xlsx, .xls, or .csv file here, or click to browse.

Primary Parameters

100 µM
50 µM
30 µM
15 µM
Combination Index (CI) Calculating
0.600
dA/DA + dB/DB = 0.300 + 0.300 = 0.600
Evaluating dose interaction...

Cartesian Isobologram Plot

1 Dose Plotted

Data points falling below the dashed diagonal isobole (CI = 1.0) represent synergistic combinations.

CI < 0.9
Synergy
0.9 ≤ CI ≤ 1.1
Additivity
CI > 1.1
Antagonism

Loewe Additivity & High-Throughput Checkerboard Screening

A reference framework for pharmacodynamic synergy and combination therapy evaluation

The Loewe Equation

The Loewe Additivity Model computes the Combination Index (CI) as:

CI = (dA / DA) + (dB / DB)
  • dA, dB: Doses of Drug A and Drug B in the combination.
  • DA, DB: Standalone equipotent doses (e.g., IC₅₀ or MIC).

Expected Excel Format

The uploaded Excel file should have columns matching:

Sample_ID, Dose_A, Dose_B, Solo_DA, Solo_DB

If Solo_DA or Solo_DB are omitted in rows, the global standalone IC₅₀ values from the top parameters panel are used automatically.