PHARM/PCS V5 · Procedure 10 Dose-Response and Potency
Relative Potency I
Find how many times more potent a test drug is than a standard, from a 2 and 2 assay or from full dose-response lines.
What it computes
Computes the potency ratio between two drugs from dose-response data. Two modes are supported, auto-detected from the number of points per drug:
- 2 and 2 assay: exactly two doses of each drug, at the same dose levels. Uses the closed-form Equation 10.2.
- Complete dose-response: more than two points per drug. Uses linear regression on log dose and measures the horizontal distance between the parallel lines.
Inputs and outputs
You provide
- The test drug's dose-response data first, then one or more standards, in the same block format
- For a 2 and 2 assay: two doses per drug, at the same dose levels
PHARM/PCS reports
- The relative potency of the test drug against each standard
- A plot of the test and standard dose-response lines
When to use it
When you want to know how many times more potent one drug is than another (or a standard) from their dose-response curves. Run Procedure 6 first to confirm parallelism, since a potency ratio only means something when the lines are parallel, and step up to Procedure 11 for confidence limits on the ratio.
Reading the results
The ratio is the horizontal distance between parallel log-dose lines, so parallelism is everything; a non-parallel pair gives a ratio that changes with response level and isn't a single number. The 2-and-2 shortcut is efficient but fragile, so a full curve is more robust when you have the points.
Several standards in one run
Like the 1986 program, the procedure detects which kind of assay you entered and applies the matching formula. Add more blocks and each standard is compared with the test drug in the same run. For a 2 and 2 assay it checks that both drugs share the same doses and tells you plainly if they do not.
This page describes the procedure. Calculations run inside the licensed PHARM/PCS V5 application. PHARM/PCS is a trademark of MCS Scientific LLC.